HK1242798B - Satellite radio-controlled watch - Google Patents

Description

Satellite radio clock

Technical Field

The present invention relates to a satellite radio clock.

Background Art

Satellite radio-controlled timepieces, which receive satellite radio waves containing both time and location information and adjust their time, are now being offered for practical use. Automatic time zone determination based on location information obtained from satellite radio waves is necessary to determine which time zone the current location belongs to.

The following patent document 1 describes an electronic device that receives satellite radio waves sent from a positioning information satellite to obtain positioning information and time information, sets only one time difference data for each segment divided into a certain size, stores block data composed of a specified number of segments without duplication, and obtains the time difference data of the segment corresponding to the positioning information in the block data.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Laid-Open No. 2010-210276

Summary of the Invention

Problems to be solved by the invention

Time zone boundaries do not necessarily follow longitude; instead, they curve in complex patterns depending on national borders and topography. Therefore, determining the time zone to which a satellite radio clock belongs requires data that can identify the time zone to which each location on the Earth's surface belongs. It is thought that such data could be used to divide the Earth's surface into a very detailed grid, assigning a time zone to each grid. However, this would require enormous storage capacity and increase the computational burden, making it unsuitable in terms of cost and power consumption.

In this regard, Patent Document 1 discloses a method for reducing data volume by aggregating a predetermined number of segments (grids) as block data and storing a correspondence between the blocks corresponding to the location information and the storage addresses corresponding to the blocks, thereby aggregating block data with the same arrangement of time difference data. However, while this method can be expected to achieve a certain degree of data reduction by aggregating the blocks with an appropriately set block size, it still requires a large amount of storage capacity, as it requires time difference data for each grid into which the ground surface is divided.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a satellite radio timepiece having a further reduced storage capacity for information used to determine a time zone from position information.

Technical solutions to problems

The invention disclosed in this application for solving the above-mentioned problems has multiple aspects, and the outline of representative aspects of these aspects is as follows.

(1) A satellite radio clock, characterized in that it comprises: a receiving unit that receives satellite radio waves including time information and position information; a storage unit that stores intersection information indicating the position of an intersection of a baseline and a time zone boundary line and time difference partition information of an area to which the intersection belongs, which is a wedge-shaped or strip-shaped area adjacent to the baseline, wherein the baseline is a baseline along a great circle orthogonal to a specific great circle of the earth or a baseline along a specific great circle of the earth or a circle parallel to the great circle; and a determination unit that determines a time zone based on the position information, the intersection information, and the time difference partition information.

(2) The satellite radio timepiece described in (1) further includes a time difference detail determination unit that determines at least one of daylight saving time and a city based on at least the position information, the intersection information, and the time difference zone information.

(3) In the satellite radio clock described in (1) or (2), the storage unit stores at least address information and time difference partition/intersection information, the address information includes an address representing at least any one of the time difference partition information and the intersection information according to each baseline, the time difference partition/point information includes the time difference partition information and the intersection information, and the time difference partition information and the intersection information can be viewed using the address according to each baseline to which they belong.

(4) In the satellite radio timepiece described in (3), the storage unit stores adjacent intersection point information included in the time difference zone/intersection point information.

(5) In the satellite radio clock described in (3) or (4), the address is the starting address of the time difference partition information and the intersection information of each of the baselines to which it belongs, and the time difference partition/intersection information includes a symbol representing the end point of the data of each of the baselines to which it belongs.

(6) In the satellite radio timepiece according to any one of (1) to (5), the storage unit stores time difference details information including at least any one of time zone information, daylight saving time information, and city information associated with the time difference partition.

(7) In the satellite radio timepiece according to any one of (1) to (6), the specific great circle is the equator.

(8) In the satellite radio timepiece according to any one of (1) to (7), the partitions are specified by two adjacent reference lines and a line orthogonal to the reference lines.

(9) The satellite radio clock described in (8) further includes an exception processing range setting unit, which uses the range specified by the two adjacent baselines and the line perpendicular to the two baselines separated by a specified distance as the exception processing range, and when the position represented by the position information is within the exception processing range, the time zone determination unit maintains the time zone.

(10) In the satellite radio clock described in any one of (1) to (9), the storage unit stores second intersection information indicating the position of the intersection of a second baseline adjacent to the first baseline and the boundary line, i.e., the second intersection, in association with first intersection information indicating the position of the first intersection between the first baseline and the boundary line, and the area is specified by the first baseline, the second baseline, and the line connecting the first intersection and the second intersection.

(11) The satellite radio clock described in (10) further includes an exception processing range setting unit, which sets a specified range including the intersection as an exception processing range, and when the position represented by the position information is within the exception processing range, the time zone determination unit maintains the time zone.

(12) In the satellite radio timepiece described in (11), the exception processing range is a range specified by the two adjacent baselines, a line passing through the first intersection and perpendicular to the baseline, and a line passing through the second intersection and perpendicular to the baseline.

(13) In the satellite radio clock described in (11), the exception processing range is an area specified by two adjacent baselines, a line parallel to the line connecting the first intersection point and the second intersection point and passing through the first intersection point, and a line parallel to the line connecting the first intersection point and the second intersection point and passing through the second intersection point.

(14) In the satellite radio timepiece described in any one of (1) to (13), when the time zone information associated with the time zone information indicates an indeterminate time zone, the time zone determination unit determines whether to maintain the time zone or adopt a specific time zone.

(15) The satellite radio timepiece described in any one of (1) to (14) further includes a high-latitude processing unit that maintains the time zone or adopts a specific time zone when the position indicated by the position information is above a predetermined latitude.

Effects of the Invention

According to the above-mentioned aspect (1) of the present invention, a satellite radio timepiece can be obtained in which the storage capacity of information for determining the time zone from position information is further reduced.

Furthermore, according to the above-mentioned aspect (2) of the present invention, a satellite radio timepiece can be obtained that determines a time difference more detailed than a time zone.

Furthermore, according to the above-mentioned aspect (3) of the present invention, a satellite radio-controlled timepiece can be obtained that stores time zone information and intersection information without duplication.

Furthermore, according to the above-mentioned aspect (4) of the present invention, a satellite radio timepiece can be obtained that can determine the time zone with higher accuracy based on the position information.

Furthermore, according to the above-mentioned aspect (5) of the present invention, a satellite radio timepiece can be obtained which stores information for determining a time zone based on position information in a variable length.

Furthermore, according to the above-mentioned aspect (6) of the present invention, a satellite radio timepiece can be obtained that stores time differences in more detail than time zones.

Furthermore, according to the above-mentioned aspect (7) of the present invention, a satellite radio clock can be obtained that uses a longitude or a latitude as a reference line.

Furthermore, according to the above-mentioned aspect (8) of the present invention, a satellite radio clock can be obtained in which the intersection points of the reference line and the time zone boundary line correspond one-to-one with the time zone divisions.

Furthermore, according to the above-mentioned aspect (9) of the present invention, a satellite radio timepiece can be obtained in which the time difference does not change in a predetermined area including the boundaries of time zones.

Furthermore, according to the above-mentioned aspect (10) of the present invention, a satellite radio timepiece can be obtained that specifies the area for determining the time zone more accurately relative to the time zone boundary line.

Furthermore, according to the above-mentioned aspect (11) of the present invention, a satellite radio timepiece can be obtained in which the time difference remains constant near the boundary of time zones.

Furthermore, according to the above-mentioned aspect (12) of the present invention, a satellite radio timepiece can be obtained in which the time difference remains constant within a range including the time zone boundary and within a range enclosed by two lines perpendicular to the reference line.

Furthermore, according to the above-mentioned aspect (13) of the present invention, a satellite radio clock can be obtained in which the time difference remains constant within a range including the time zone boundary and within a range specified by a line connecting the intersection of the reference line and the time zone boundary.

Furthermore, according to the above-mentioned aspect (14) of the present invention, a satellite radio timepiece can be obtained that can display the time even if the time zone is not fixed.

Furthermore, according to the above-mentioned aspect (15) of the present invention, a satellite radio timepiece can be obtained that suppresses frequent time corrections.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a plan view showing an example of the appearance of a satellite radio-controlled watch according to a first embodiment of the present invention.

FIG2 is a block diagram showing the internal structure of a satellite radio-controlled wristwatch according to the first embodiment of the present invention.

FIG3 is a functional block diagram showing the functions implemented by the satellite radio-controlled wristwatch according to the first embodiment of the present invention.

FIG4 is a schematic diagram showing time zone boundaries and time zone division areas handled in the satellite radio-controlled watch according to the first embodiment of the present invention.

FIG5 is a schematic plan view showing time zone boundaries and time zone division areas handled in the satellite radio-controlled wristwatch according to the first embodiment of the present invention.

FIG6 is a diagram showing a first example of time difference partition areas handled in the satellite radio-controlled wristwatch according to the first embodiment of the present invention.

FIG. 7 is a diagram showing address information stored in the satellite radio-controlled wristwatch according to the first embodiment of the present invention.

FIG8 is a diagram showing time zone/intersection information stored in the satellite radio-controlled wristwatch according to the first embodiment of the present invention.

FIG. 9 is a diagram showing detailed time difference information stored in the satellite radio-controlled wristwatch according to the first embodiment of the present invention.

FIG10 is a diagram showing a second example of time difference partition areas handled in the satellite radio-controlled wristwatch according to the first embodiment of the present invention.

FIG11 is a flowchart showing the time adjustment process performed by the satellite radio-controlled watch according to the first embodiment of the present invention.

FIG12 is a diagram showing an exception processing range set in a satellite radio-controlled wristwatch according to a first modification of the first embodiment of the present invention.

FIG13 is a diagram showing an exception processing range set in a satellite radio-controlled wristwatch according to a second modification of the first embodiment of the present invention.

14 is a flowchart showing exceptional processing for time adjustment performed by satellite radio-controlled wristwatches according to the first and second modified examples of the first embodiment of the present invention.

FIG15 is a diagram showing a first example of time difference partition areas handled in the satellite radio-controlled watch according to the second embodiment of the present invention.

FIG. 16 is a diagram showing time zone/intersection information stored in the satellite radio-controlled watch according to the second embodiment of the present invention.

FIG17 is a diagram showing a second example of time difference partition areas handled in the satellite radio-controlled watch according to the second embodiment of the present invention.

FIG18 is a diagram showing a third example of time difference partition areas handled in the satellite radio-controlled watch according to the second embodiment of the present invention.

FIG19 is a flowchart showing the time adjustment process performed in the satellite radio-controlled wristwatch according to the second embodiment of the present invention.

FIG20 is a diagram showing an example of an exception processing range in a satellite radio-controlled wristwatch according to a modification of the second embodiment of the present invention.

FIG21 is a flowchart showing exceptional processing for time adjustment performed in a satellite radio-controlled wristwatch according to a modification of the second embodiment of the present invention.

FIG22 is a schematic diagram showing another example of time zone boundaries and time zone division areas.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[First embodiment]

FIG1 is a plan view showing an example of the appearance of a satellite radio-controlled watch 1 according to a first embodiment of the present invention. The figure shows a dial 53, which is located within the main body (watch case) serving as the exterior of the satellite radio-controlled watch 1, and hour, minute, and second hands 52a, 52b, and 52c, which indicate the time. Furthermore, an operating unit 60, namely a crown 60a and a button 60b, is located on the side surface at the 3 o'clock position of the main body, allowing the user of the satellite radio-controlled watch 1 to perform various operations.

The satellite radio-controlled watch 1 has a windshield cover made of a transparent material such as glass attached to the main body, covering the dial 53. Furthermore, a back cover is attached to the main body opposite the windshield cover. In this specification, the direction in which the windshield cover of the satellite radio-controlled watch 1 is attached (toward the front of the paper in FIG1 ) is referred to as the front side, and the direction in which the back cover is attached (toward the back of the paper in FIG1 ) is referred to as the back side.

A solar cell 42 is located on the back side of the character plate 53, which can generate electricity using light incident from the front side. Therefore, the character plate 53 is formed of a material that can transmit light to a certain extent. A patch antenna for receiving satellite radio waves is located in an area that does not overlap with the solar cell 42. The front side of the patch antenna is the receiving surface for receiving radio waves from the satellite. The receiving surface of the patch antenna, the light-receiving surface of the solar cell 42, and the character plate 53 are arranged parallel to each other, all facing the front side. Alternatively, a chip antenna or an inverted F antenna can be used instead of the patch antenna.

In addition, in this specification, the term satellite radio-controlled watch is used to refer to a watch that has the function of receiving satellite signals from satellites such as GPS (Global Positioning System) satellites that transmit information about date and time (time information), and correcting the internal time that is the time information maintained inside the watch based on the time information included therein. However, the present invention is not limited to satellite radio-controlled watches, but can also be applied to small clocks that are not watches, such as pocket watches. In addition, the satellite radio-controlled watch also receives position information contained in the satellite signal. In addition, the satellite that transmits the satellite signal received by the satellite radio-controlled watch may also be a satellite used for purposes other than GPS satellites or a satellite planned to be used in the future, such as the GLONASS system, the European Galileo system, the BeiDou satellite navigation system (COMPASS), etc.

Satellite radio waves transmitted from GPS satellites are phase-shift keyed (PSK) modulated onto a carrier wave (L1 band) with a frequency of approximately 1.6 GHz. The signal encoded into the satellite radio wave is a superposition of a pseudorandom number (PRN) unique to each GPS satellite and a satellite signal containing time information. The satellite radio-controlled watch 1 receives multiple satellite radio waves transmitted from multiple satellites and determines which satellite's PRN correlates most strongly with each other to identify the satellite from which each of the multiple received satellite radio waves originates. In this specification, this satellite identification process is referred to as satellite radio tracking. The satellite signal includes time information, which consists of a TOW (Time of Week) indicating the current time, based on the start of the week (00:00 AM on Sunday), and a week number WN indicating the current week from a predetermined reference time. Therefore, depending on the situation, the satellite radio-controlled watch 1 may receive only the TOW or both the TOW and the week number WN. Furthermore, because GPS time deviates from Coordinated Universal Time due to leap seconds, GPS satellites also transmit leap second information to correct for this deviation. Therefore, the satellite radio-controlled watch 1 receives not only time information from the GPS satellites, but also this leap second information. Furthermore, the satellite signals also include position information. This position information includes the almanac, which provides position information for all satellites, and the ephemeris, which provides position information for each satellite. Based on this received position information, the satellite radio-controlled watch 1 calculates the distance to the multiple GPS satellites orbiting overhead and the latitude, longitude, and altitude of its current location.

In the example of the satellite radio-controlled watch 1 shown in FIG1 , the character plate 53 is surrounded by the characters "RX" (reception in progress) 53a, "OK" (reception successful) 53b, "NG" (reception failed) 53c, and "NA" (unclear process) 53d. The reception successful character 53b and the reception failed character 53c are indices (indices) that indicate the success or failure of the reception process performed by the satellite radio-controlled watch 1, for example, using the second hand 52c. Furthermore, the reception in progress character 53a indicates that the reception process is in progress. The unclear process character 53d indicates that an unclear process, described in detail later, has been performed. These indices can also be used to indicate the result of the previous reception process before the reception process is performed.

City display 53e indicates the representative city of the currently set time zone. In the example shown in FIG1 , the characters "LON" are used to indicate that the representative city is London. Alternatively, it may indicate whether daylight saving time is currently set. For example, the second hand 52c may indicate whether daylight saving time is in effect in the set time zone, or a separate auxiliary hand may be provided to indicate this.

The design of the satellite radio-controlled watch 1 shown in Figure 1 is an example. In addition to the design shown here, the main body may be designed in a polygonal form instead of a circular form. The presence, number, and placement of the crown 60a and push-button 60b are arbitrary. Furthermore, in this embodiment, the hands include the hour hand 52a, minute hand 52b, and second hand 52c. However, this is not limiting. The second hand 52c may be omitted, or various indicators such as the day of the week, time zone, the presence or absence of daylight saving time, radio reception status, and battery life may be added, as well as a date display.

The main body of the satellite radio watch 1 houses a driving mechanism 50 for driving the hands, a secondary battery 40 for storing power generated by a solar cell 42, a control circuit 30 for controlling the operation of the satellite radio watch 1, a receiving circuit 20 for processing received satellite signals, etc. The details will be described later.

FIG2 is a block diagram showing the internal structure of a satellite radio-controlled watch 1. As shown in the figure, the satellite radio-controlled watch 1 includes an antenna 10, a receiving circuit 20, a control circuit 30, a secondary battery 40, a switch 41, a solar cell 42, a drive mechanism 50, a time display unit 51, and an operating unit 60.

The antenna 10 receives satellite radio waves transmitted from a satellite as radio waves including time information. In particular, in this embodiment, the antenna 10 is a patch antenna that receives satellite radio waves transmitted from a GPS satellite.

The receiving circuit 20 decodes the satellite radio waves received by the antenna 10 and outputs a bit string (received data) indicating the contents of the satellite signal obtained as a result of the decoding. Specifically, the receiving circuit 20 includes a high-frequency circuit (RF circuit) 21 and a decoding circuit 22.

The high-frequency circuit 21 is an integrated circuit operating at high frequencies. It amplifies and detects the analog signal received by the antenna 10 and converts it into a baseband signal. The decoding circuit 22 is an integrated circuit performing baseband processing. It decodes the baseband signal output by the high-frequency circuit 21 to generate a bit string representing the content of the data received from the GPS satellite and outputs it to the control circuit 30.

The control circuit 30 is an information processing device such as a microcomputer, and includes a calculation unit 31 , a ROM (Read Only Memory) 32 , a RAM (Random Access Memory) 33 , an RTC (Real Time Clock) 34 , and a motor drive circuit 35 .

The calculation unit 31 performs various information processing according to the programs stored in the ROM 32. Details of the processing performed by the calculation unit 31 in this embodiment will be described later. The RAM 33 functions as the working memory of the calculation unit 31, into which data to be processed by the calculation unit 31 is written. In particular, in this embodiment, a bit string (received data) representing the contents of the satellite signal received by the receiving circuit 20 is sequentially written to a buffer area within the RAM 33. The RTC 34 supplies a clock signal used for timekeeping within the satellite radio-controlled watch 1. In the satellite radio-controlled watch 1 of this embodiment, the calculation unit 31 corrects the internal time, which is kept using the signal supplied from the RTC 34, based on the satellite signal received by the receiving circuit 20, thereby determining the time to be displayed on the time display unit 51 (displayed time). Furthermore, the motor drive circuit 35 outputs a drive signal for driving the motor included in the drive mechanism 50 (described later) based on the determined displayed time. Thus, the displayed time generated by the control circuit 30 is displayed on the time display unit 51.

The secondary battery 40 is a battery that stores electricity generated by the solar cell 42 and is, for example, a lithium-ion battery. This stored electricity is supplied to the receiving circuit 20 or the control circuit 30. A switch 41 is provided midway along the power supply path from the secondary battery 40 to the receiving circuit 20. This switch 41 is switched on/off by a control signal output by the control circuit 30. By switching the switch 41 on/off by the control circuit 30, the operating timing of the receiving circuit 20 is controlled. The receiving circuit 20 operates only while power is supplied from the secondary battery 40 via the switch 41, decoding satellite radio waves received by the antenna 10 during this period.

The solar cell 42 is disposed on the back side of the dial 53 , generates electricity using external light such as sunlight that hits the satellite radio-controlled watch 1 , and supplies the generated electricity to the secondary battery 40 .

The drive mechanism 50 includes a stepping motor and a gear train that operate in response to a drive signal output from the aforementioned motor drive circuit 35. The rotation of the stepping motor is transmitted through the gear train, thereby rotating the hands 52. The time display unit 51 includes the hands 52 and a dial 53. The hands 52 include an hour hand 52a, a minute hand 52b, and a second hand 52c. The rotation of these hands 52 on the dial 53 displays the current time.

The operating unit 60, which includes a crown 60a and buttons 60b, receives operations from the user of the satellite radio-controlled watch 1 and outputs the details of these operations to the control circuit 30. The control circuit 30 performs various processes based on the details of the operational inputs received by the operating unit 60. In particular, in this embodiment, the control circuit 30 receives satellite signals based on the user's operational inputs to the operating unit 60.

The following describes a specific example of the processing performed by the calculation unit 31 of the control circuit 30 in this embodiment. As shown in Figure 3, by executing the program stored in the ROM 32, the calculation unit 31 can functionally implement the functions of the time zone determination unit 31a, the time difference details determination unit 31b, the exception processing range setting unit 31c, the high latitude processing unit 31d, and the time adjustment unit 31e.

The time zone determination unit 31a determines the time zone to which the satellite radio-controlled watch 1 belongs based on the position information 33a stored in the RAM 33 and the time zone information and intersection information included in the time zone/intersection information 32b stored in the ROM 32. The ROM 32, serving as a storage unit, stores address information 32a for each reference line. This address information 32a includes an address indicating at least one of the time zone information and the intersection information. Furthermore, the ROM 32 stores time zone/intersection information 32b, which includes the time zone information and the intersection information. The time zone information and the intersection information can be accessed (referenced, compared) using the address for each reference line. Furthermore, the ROM 32 stores time zone details 32c, associated with the time zone, including at least one of time zone information and daylight saving time information and city information.

The time difference detail determination unit 31b determines at least one of daylight saving time and a city based on at least the position information, the intersection information, and the time difference zone information.

The exception processing range setting unit 31c sets the range for the time zone determination unit 31a to perform exception processing. When the position indicated by the position information 33a is within the exception processing range, the time zone determination unit 31a maintains the time zone unchanged.

When the location indicated by the position information 33a is above a predetermined latitude, the high latitude processing unit 31d maintains the time zone or sets it to a specific time zone. In the satellite radio-controlled watch 1 of this embodiment, when the location indicated by the position information 33a is above 80° north latitude or 80° south latitude, the high latitude processing unit 31d maintains the time zone unchanged.

The time adjustment unit 31e receives the time difference determined by the time difference detail determination unit 31b and adjusts the internal time kept within the satellite radio-controlled watch 1.

FIG4 is a schematic diagram showing time zone boundaries 71 and time zone divisions 70 processed by the satellite radio-controlled watch 1 according to the first embodiment of the present invention. FIG5 is a schematic diagram showing, in plan view, time zone boundaries 71 and time zone divisions 70 processed by the satellite radio-controlled watch according to the first embodiment of the present invention.

Figures 4 and 5 show two time zone boundaries 71 as examples. The time zone boundaries 71 shown in these figures are broken lines with their ends at the North Pole (90° north latitude) and the South Pole (90° south latitude). However, time zone boundaries 71 are not limited to ending at the North Pole and the South Pole; a closed area on the Earth's surface may also be selected as a time zone.

In the satellite radio-controlled watch 1 of this embodiment, a reference line along a great circle orthogonal to a specific great circle of the Earth can be used as a reference line for designating the time zone division area 70. Specifically, the specific great circle is the equator (the latitude of 0°), and the great circle orthogonal to the specific great circle is a meridian. In this embodiment, the time zone division area 70 is the area sandwiched between two meridian lines serving as the two reference lines. As described later, a reference line along a specific great circle of the Earth or a circle parallel to the great circle can also be used as a reference line. In this case, if the specific great circle is the equator, the circle parallel to the specific great circle is a latitude. In this embodiment, the time zone division area 70 is defined by dividing the northeast, northwest, southeast, and southwest regions into 1-minute longitude intervals. In other words, the time zone division area 70 is a wedge-shaped area (or a strip-shaped area when represented using the Mercator projection) with a 1-minute longitude, located between 0° and 90° north latitude or 0° and 90° south latitude.

In the examples shown in Figures 4 and 5, the time zone zone for the area enclosed by the time zone boundary 71 is "1." Furthermore, the time zone zone to the west of this zone is "0," and the time zone zone to the east of this zone is "2." As will be described later, a time zone zone is associated with at least one of a time zone, daylight saving time, and city. By determining to which time zone the satellite radio-controlled watch 1 belongs, detailed time adjustment can be performed.

4 and 5, the time zone 70 is located in the northeast. In the satellite radio-controlled watch 1 of this embodiment, the earth's surface is divided into four zones: northeast, northwest, southeast, and southwest, eliminating the need to process negative latitudes and simplifying the data structure.

FIG6 illustrates a first example of a time zone zone 70 processed by the satellite radio-controlled watch 1 according to the first embodiment of the present invention. In this example, the time zone zone 70 is the area between 0° and 90° north latitude and between E1 and E2 east longitude. A first reference line 72 designating the time zone zone 70 is the meridian of longitude E1 east, and a second reference line 73 is the meridian of longitude E2 east. The first reference line 72 intersects the time zone boundary line 71 four times. These intersections are referred to as the first intersection at latitude N1 north, the second intersection at latitude N2 north, the third intersection at latitude N3 north, and the fourth intersection at latitude N4 north.

The time zone zones handled by the satellite radio-controlled watch 1 of this embodiment are wedge-shaped or strip-shaped areas adjacent to a reference line. Each zone is defined by the intersection of the reference line and the time zone boundary line 71. Specifically, each zone is defined by two adjacent reference lines (a first reference line 72 and a second reference line 73) and a line perpendicular to the reference lines (a zone boundary line 74). Zone boundary line 74 is a latitude line. In this example, within the range of east longitudes E1 and E2, the time zone zone for the area from 0°N to N1°N is "1," the time zone zone for the area from N1 to N2°N is "0," the time zone zone for the area from N2 to N3°N is "1," the time zone zone for the area from N3 to N4°N is "0," and the time zone zone for the area from N4 to 80°N is "1." Regardless of the east longitude, the time zone zone for the area above 80°N is "NA" (Not Applicable), meaning no time zone is assigned. This setting also applies to areas above 80° S. The reason for this is that if time zone divisions are set near the poles at latitudes above 80° S, relatively small movements near the poles will cause large changes in longitude, resulting in frequent changes in the time zone to which the satellite radio-controlled watch 1 belongs, which would in turn impair practicality.

When the location indicated by the location information 33a is above a specified latitude, the high latitude processing unit 31d maintains the time zone or sets it to a specific time zone. In the satellite radio-controlled watch 1 of this embodiment, when the latitude (north or south) of the current location is above 80°, the high latitude processing unit 31d sets the time zone to UTC (Coordinated Universal Time). The latitude of 80° is used as a reference here as an example. The high latitude processing unit 31d may also set the time zone to UTC when the latitude of the current location is above 85°, for example. Alternatively, it may set another time zone difference instead of UTC+0. Furthermore, the high latitude processing unit 31d may determine to maintain the time zone when the location indicated by the location information 33a is above a specified latitude. In this case, the time zone in polar regions changes depending on the longitude at which one approaches the polar regions. Alternatively, the user of the satellite radio-controlled watch 1 may be able to select whether the high latitude processing unit 31d maintains the time zone or sets it to a specific time zone.

In the satellite radio-controlled watch 1 of this embodiment, when the high-latitude processing unit 31d performs processing to maintain the time zone or set the time zone to a specific time zone, the second hand 52c indicates the "NA" time zone by indicating the "undefined processing" character 53d. This allows the user of the satellite radio-controlled watch 1 to confirm that the time zone is "undefined" during processing. The satellite radio-controlled watch 1 of this embodiment can reduce the need for frequent time adjustments in polar regions. Furthermore, the execution of exceptional processing can be visually confirmed.

The time zone determination unit 31a of the satellite radio-controlled watch 1 of this embodiment calculates the current location from the position information 33a included in the satellite signal and determines to which time zone zone 70 the current location belongs. Furthermore, the latitude of the intersection of the baseline specifying the time zone zone 70 and the time zone boundary line 71 is compared with the latitude of the current location to determine to which time zone the current location belongs, and the time zone of the current location is determined based on the time zone zone. Furthermore, the time zone details determination unit 31b determines the daylight saving time and city of the current location based on the time zone zone. Once the time zone and daylight saving time are determined, the time difference can be fully determined. The following describes the various information required for this time zone determination.

FIG7 illustrates address information 32a stored in the ROM 32 of the satellite radio-controlled watch 1 according to the first embodiment of the present invention. Address information 32a includes an address representing at least one of time zone information and intersection information for each baseline (in this embodiment, for each minute of longitude). In this embodiment, the address represents the starting address of the time zone information and intersection information for each baseline. Address information 32a is stored in the order of northeast, northwest, southeast, and southwest. While the figure shows address information 32a in detail for the northeast region as an example, similar information is stored for the northwest, southeast, and southwest regions.

To simplify the data structure, the figure shows the addresses of the memory used to store address information 32a. Address = 0 stores the first starting address. This first starting address is the address of the time zone/intersection information 32b to be referenced when the current location belongs to the time zone between 0°0′ and 0°1′ east longitude. Similarly, address = 1 stores the second starting address, which is the address of the time zone/intersection information 32b to be referenced when the current location belongs to the time zone between 0°1′ and 0°2′ east longitude. In this embodiment, the time zones are divided into 1-minute longitude zones for the northeast, northwest, southeast, and southwest regions. Therefore, for example, the number of address information 32a in the northeast region is 180 × 60 = 10,800. Since the same applies to the northwest, southeast, and southwest regions, the total number of address information 32a is 10,800 × 4 = 43,200. The address information 32a in the northwest region is stored in addresses = 10800 to 21599, the address information 32a in the southeast region is stored in addresses = 21600 to 32399, and the address information 32a in the southwest region is stored in addresses = 32400 to 43199.

The address information 32a may be repeated for multiple time difference partition areas. When the time zone boundary line is a line of a certain latitude, multiple baselines intersect with the same latitude. In this case, if the time difference partition information and intersection information are stored separately for multiple time difference partition areas specified by multiple baselines, a waste of storage capacity will occur. Therefore, for multiple time difference partition areas with the same time difference partition information and intersection information, the same starting address is stored, and the same time difference partition information and intersection information are referenced. This allows the time difference partition information and intersection information to be stored without duplication, reducing storage capacity. In addition, the amount of stored time difference partition information and intersection information is different for each time difference partition area. Therefore, if each time difference partition information and intersection information is stored in a manner to ensure a certain data length, it will have to match the longest data length, resulting in unused data areas for most of the time difference partition areas and a waste of storage capacity. In this regard, if the start address of the time difference partition/intersection information 32b is specified using the address information 32a, the time difference partition information and intersection information can be stored in a variable length for each time difference partition area, thereby making it possible to use the storage capacity without waste.

FIG8 shows the time zone/intersection information 32b stored in the satellite radio-controlled watch 1 according to the first embodiment of the present invention. The intersection information indicates the location of the intersection between the baseline and the time zone boundary line 71. The time zone information is associated with the time zone information, daylight saving time information, and city information for the area (a wedge-shaped or strip-shaped area adjacent to the baseline) where the intersection of the baseline and time zone boundary line 71 resides. The time zone/intersection information 32b includes the time zone information and the intersection information. These information can be referenced using the addresses included in the address information 32a for each baseline to which the time zone/intersection information belongs.

FIG8 shows the time zone information and intersection information for the time zone area 70 shown in FIG6 . The time zone/intersection information 32b has a data structure that alternately stores the time zone information and the intersection information. The memory storing the time zone/intersection information 32b stores information indicating a time zone of 1 at the starting address 0, and the latitude of the first intersection, 8°34′(N1), at the next address. This data structure indicates that the time zone within the range of longitudes E1 to E2 east and latitudes 0° to 8°34′(N1) north is "1." Similarly, the time zone/intersection information 32b indicates that the time zone for the range between longitudes E1 and E2 east and latitudes 8°34′ (N1) and 28°6′ (N2) north is "0," the time zone for the range between latitudes 28°6′ (N2) and 45°24′ (N3) north is "1," and the time zone for the range between latitudes 45°24′ (N3) and 65°0′ (N4) north is "0." Furthermore, the time zone information "Time Zone = 1" stored at address 8 and the "END" information (a symbol indicating the end point of the data for each reference line) stored at address 9 indicate that the time zone for the range between latitudes 65°0′ (N4) and 80° north is "1," indicating that there is no intersection between the first reference line 72 and the time zone boundary line 71 north of 65°0′ (N4). The "END" information stored at address 9 can also be set to "Intersection = 80°." The information stored after the start address = 10 is the time zone information and intersection information for the time zone area located east of the second reference line 73. Thus, the time zone/intersection information 32b stored in the satellite radio-controlled watch 1 of this embodiment has a data structure in which the time zone information and intersection information correspond one-to-one.

Furthermore, the structure of address information 32a and time zone/intersection information 32b is not limited to the above-described structure. For example, address information 32a may not be stored. Instead, the above-described data structure may be used as time zone/intersection information 32b, and time zone/intersection information 32b may be sequentially read starting from address = 0. The number of "end" data is counted to obtain time zone information and intersection information corresponding to the longitude of the current location. Alternatively, address information 32a may not be stored, and time zone information and intersection information may be stored with equal data length for each time zone area 70. In this case, the corresponding time zone information and intersection information can be obtained by simply determining the time zone area 70 to which the current location belongs and offsetting the storage address of time zone/intersection information 32b from address = 0 by an amount corresponding to the longitude of the current location.

FIG9 shows detailed time zone information 32c stored in the satellite radio-controlled watch 1 according to the first embodiment of the present invention. The detailed time zone information 32c includes time zone information associated with the time zone information, as well as at least one of daylight saving time information and city information. In this embodiment, the detailed time zone information 32c indicates the time zone, daylight saving time, and city information associated with each time zone. The time zone is represented by an offset from UTC (Coordinated Universal Time). The time zone in the time zone "0" coincides with UTC, the time zone in the time zone "1" is one hour ahead of UTC, and the time zone in the time zone "2" is one hour ahead of UTC. Daylight saving time is the time observed during the summer months of the year. In the time zone "0," daylight saving time is not in effect, so "NA" (denoting no designation) is stored. In the time zone "1," daylight saving time is observed from date ST1 to date ED1, and the time is one hour ahead. Furthermore, in the area of time zone "2," daylight saving time is observed from date ST2 to ED2, advancing time by 0.5 hours. The areas of time zone "1" and "2" share the same time zone, but differ in the period of daylight saving time implementation and the amount of correction. "City" indicates the name of a representative city in each time zone. Specific names are not listed here, but for example, the area of time zone "0" is named "A," the area of time zone "1" is named "B," and the area of time zone "2" is named "C."

FIG10 illustrates a second example of a time zone zone 70 handled by the satellite radio-controlled watch 1 according to the first embodiment of the present invention. In this example, the area bounded by a time zone boundary line 71 passing through the second intersection of latitude N2 and a third intersection of latitude N3 represents an area where international time zone agreement has not been reached. An example of such an area is a disputed region. In this case, in the satellite radio-controlled watch 1 according to this embodiment, the time zone zone bounded by a zone boundary line 74 passing through the second intersection of latitude N2 and a third intersection of latitude N3 is designated as NA (a symbol indicating that the zone is not set). When the time zone zone is NA, the associated time zone is indicated as "undefined" in the time zone details information 32c. When the time zone associated with the time zone information is indicated as "undefined," the time zone determination unit 31a determines whether to maintain the time zone or set it to a specific time zone. In the satellite radio-controlled watch 1 according to this embodiment, when the time zone is "undefined," the time zone determination unit 31a determines to maintain the time zone. In the example shown in FIG10 , if the range between longitudes E1 and E2 east moves northward from latitude 0° north, it initially belongs to time zone "0." Therefore, according to the time zone detailed information 32c shown in FIG9 , the associated time zone is UTC+0. When crossing latitude N1 north, it enters time zone "2," a region where the time zone is UTC+1 and +0.5 hours of daylight saving time is implemented from ST2 to ED2. Further north, crossing latitude N5 north, it enters time zone "1," a region where the time zone is UTC+1 and +1 hour of daylight saving time is implemented from ST1 to ED1. Further north, crossing latitude N6 north, it enters time zone "2," a region where the time zone is UTC+1 and +0.5 hours of daylight saving time is implemented from ST2 to ED2. Further crossing north latitude N2, the zone enters time zone "NA," maintaining the time zone of UTC+1 with +0.5 hours of daylight saving time from date ST2 to date ED2. Furthermore, crossing north latitude N3, the zone enters time zone "0," and the time zone becomes UTC+0. On the other hand, if the area between longitudes E1 and E2 moves southward from 80° north latitude, it initially belongs to time zone "1," meaning the time zone is UTC+1 with +1 hour of daylight saving time from date ST1 to date ED1. Then, crossing north latitude N4, the zone enters time zone "0," and the time zone becomes UTC+0. Further crossing north latitude N3, the zone enters time zone "NA," maintaining the time zone of UTC+0. Furthermore, crossing north latitude N2, the zone enters time zone "2," and the time zone is UTC+1 with +0.5 hours of daylight saving time from date ST2 to date ED2. Furthermore, crossing N6 North Latitude enters time zone "1," where the time zone is UTC+1 and daylight saving time is +1 hour from date ST1 to date ED1. Thus, depending on the direction from which one enters an area with uncertain time zones, the time zone used by the satellite radio-controlled watch 1 varies, and the time adjustment performed by the time adjustment unit 31e also varies. Thus, the satellite radio-controlled watch 1 of this embodiment can display the time even when the time zone is uncertain.

When the time zone determination unit 31a performs the time zone uncertainty processing, the satellite radio-controlled watch 1 of this embodiment displays the uncertainty processing character 53d with the second hand 52c, indicating that the time zone is "NA." This allows the user of the satellite radio-controlled watch 1 to confirm that the time zone uncertainty processing is being performed. In this embodiment, the time zone determination unit 31a maintains the time zone when the time zone is "NA," but it can also determine to set the time zone to a specific time zone, such as UTC+0.

FIG11 is a flowchart illustrating the time adjustment process of the satellite radio-controlled watch 1 according to the first embodiment of the present invention. The satellite radio-controlled watch 1 of this embodiment begins the time adjustment process upon user operation of the operating unit 60. The watch first receives satellite radio signals ( S1 ). It then obtains the time information and position information contained in the satellite signals and stores them in the RAM 33 ( S2 ).

Next, the time zone determination unit 31a determines whether the latitude of the current position represented by the acquired position information is above 80° (S3). When the latitude of the current position is not above 80°, it is determined that the current position belongs to one of the northeast, northwest, southeast, and southwest regions (S4). Then, the numbers below the second in the longitude of the current position are rounded off (S5) to determine which time zone area the current position belongs to. For example, when the value after rounding off the numbers below the second in the east longitude of the current position is E1, it belongs to the time zone area 70 shown in Figure 6. On the other hand, when the value after rounding off the numbers below the second in the east longitude of the current position is E2, it belongs to the time zone area located on the east side of the second reference line 73.

After determining the time zone area to which the current location belongs, the corresponding starting address can be determined (S6). After determining the starting address, the address of the time zone/intersection information 32b to be referenced can be clearly determined. Then, based on the intersection information, the latitude line starting from the intersection is compared with the latitude of the current location (S7). By determining which intersection latitude the latitude of the current location is between, the time zone of the current location is determined (S8). Then, by referring to the time zone details information 32c, the time zone corresponding to the determined time zone is determined. In addition, the time zone details determination unit 31b determines the details of the time difference such as daylight saving time and city time (S9).

On the other hand, when the current latitude is greater than 80°, the high latitude processing unit 31d determines the current time zone to be UTC+0 (S10). As described above, the high latitude processing unit 31d may maintain the current time zone and inherit the previous time zone.

After determining the detailed information on the time difference at the current location of the satellite radio-controlled watch 1, the time adjustment unit 31e adjusts the time based on the information on the time difference (S11). The above process completes the time adjustment process of the satellite radio-controlled watch 1.

FIG12 shows an exception processing range 75 set in a satellite radio-controlled watch 1 according to a first variation of the first embodiment of the present invention. The time zone division area 70 shown in FIG12 is the same as the time zone division area shown in FIG6 . However, in the satellite radio-controlled watch 1 according to this variation, the exception processing range setting unit 31 c sets the exception processing range 75 near the time zone boundary.

In the time zone area 70 shown in Figure 12, the intersections of the first reference line 72 and the time zone boundary line 71 are located at north latitudes NL1, NL2, NL3, and NL4, starting from the south. Furthermore, the intersections of the second reference line 73 and the time zone boundary line 71 are located at north latitudes NR1, NR2, NR3, and NR4, starting from the south. Here, the intersection of the first reference line 72 and the time zone boundary line 71 at north latitude NL1 is referred to as the first intersection, and the intersection of the second reference line 73 and the time zone boundary line 71 at north latitude NR1 is referred to as the second intersection. The exception processing range 75 is defined by two adjacent reference lines (the first reference line 72 and the second reference line 73), a line passing through the first intersection and perpendicular to the reference lines (the latitude of north latitude NL1), and a line passing through the second intersection and perpendicular to the reference lines (the latitude of north latitude NR1). In the example shown in Figure 12, there are four exception processing ranges 75, each with a different latitudinal width. The width of the exception processing range 75 in the latitudinal direction increases or decreases according to the inclination of the time zone boundary line 71 .

In this variation, after determining the time zone area 70 to which the current location belongs, but before determining the time zone for the current location, the exception processing range setting unit 31c reads the intersection points belonging to the time zone area 70 and sets an exception processing range 75. Furthermore, when the location indicated by the position information 33a is within the exception processing range 75, the time zone determination unit 31a maintains the time zone. For example, within the range of longitudes E1 to E2 east, assuming a northward movement from a point at latitude 0° north, the satellite radio-controlled watch 1 initially belongs to time zone "1." Thereafter, even if the time zone passes north latitude NL1, the time zone remains unchanged, and time zone "1" remains. Further north, past latitude NR1, the time zone becomes "0," and the time zone changes. From this point, if the direction of travel is reversed and the time zone is southward, even if the time zone passes north latitude NR1, the time zone corresponding to time zone "0" remains unchanged. Further south, past latitude NL1, the time zone becomes "1," and the time zone changes. Therefore, according to the satellite radio-controlled watch 1 of this modification, the time difference does not change near the time zone boundary, and the original time difference is maintained.

FIG13 shows an exception processing range 75 set in a satellite radio-controlled watch 1 according to a second variation of the first embodiment of the present invention. The time zone division area 70 shown in FIG13 is the same as the time zone division area shown in FIG6 . However, in the satellite radio-controlled watch 1 of this variation, an exception processing range 75 having a constant width in the latitudinal direction is set near the time zone boundary line 71 by the exception processing range setting unit 31 c.

The exception processing range 75 shown in Figure 13 is the area that includes the intersection of the baseline and the time zone boundary line 71. It is a range specified by two adjacent baselines and a line (latitude) that is perpendicular to the two baselines and separated by a specified distance. Specifically, the exception processing range 75 that includes the intersection at north latitude NL1 and the intersection at north latitude NR1 is a range specified by the first baseline 72 and the second baseline 73 and two latitudes separated by a specified distance in the latitudinal direction. In the example shown in Figure 13, there are four exception processing ranges 75, and the widths of these exception processing ranges 75 in the latitudinal direction are equal. In this way, by presetting the latitudinal width of the exception processing range 75, the exception processing range 75 can be set independently of the inclination of the time zone boundary line. Therefore, the computational burden can be reduced.

In the satellite radio-controlled watch 1 of this variation, after determining the time zone zone 70 to which the current location belongs, and before determining the time zone zone for the current location, the exception processing range setting unit 31c reads the intersection points belonging to the time zone zone 70 and sets an exception processing range 75. If the location indicated by the position information 33a is within the exception processing range 75, the time zone determination unit 31a maintains the time zone. Thus, according to the satellite radio-controlled watch 1 of this variation, the time zone remains unchanged within the specified area, including the time zone boundaries, and the original time zone is maintained.

In the satellite radio-controlled watch 1 according to the first and second variations of this embodiment, when exceptional time adjustment processing is performed, the second hand 52c indicates the indefinite processing character 53d, indicating that processing has been performed when the time zone is "NA." This allows the user of the satellite radio-controlled watch 1 to confirm that processing has been performed when the time zone is indefinite.

FIG14 is a flowchart illustrating the exceptional processing performed by the satellite radio-controlled watch 1 according to the first and second variations of the first embodiment of the present invention. The satellite radio-controlled watch 1 according to the first and second variations begins time adjustment processing upon user operation of the operating unit 60. The watch first receives satellite radio signals ( S20 ). The watch then acquires the time information and position information contained in the satellite signals and stores them in the RAM 33 ( S21 ).

Next, the time zone determination unit 31a determines whether the latitude of the current location indicated by the acquired location information is greater than or equal to 80° (S22). If the latitude of the current location is not greater than or equal to 80°, it is determined that the current location belongs to one of the northeast, northwest, southeast, and southwest zones (S23). Next, the longitude of the current location is rounded off to the nearest second (S24) to determine which time zone zone the current location belongs to.

After determining the time zone to which the current location belongs, the corresponding starting address is determined (S25). The exception processing range setting unit 31c then reads the intersection information and sets the exception processing range 75 using the latitude line (S26). In the satellite radio-controlled watch 1 of the first modification, the exception processing range setting unit 31c sets the exception processing range 75 using the latitude line passing through the intersection of the baseline and the time zone boundary line. In the satellite radio-controlled watch 1 of the second modification, the exception processing range setting unit 31c sets the exception processing range 75 using the latitude line separated by a predetermined distance.

Next, a determination is made as to whether the location indicated by the location information 33a is within the exception handling range 75 (S27). If the current location is not within the exception handling range, the time zone/intersection information 32b is referenced from the determined starting address. Based on the intersection information, the latitude line starting from the intersection is compared with the latitude of the current location (S28). The time zone for the current location is determined by determining which intersection latitude the current location's latitude falls between (S29). Next, the time zone corresponding to the determined time zone is determined by referring to the time zone details information 32c. Furthermore, the time zone details determining unit 31b determines details of daylight saving time and time differences such as city time (S30).

On the other hand, if the current location is within the exception processing range, the time zone determination unit 31a determines to maintain the time zone (S31). Furthermore, if the current location's latitude is greater than 80°, the high latitude processing unit 31d determines the current location's time zone to be UTC+0 (S32). As previously mentioned, the high latitude processing unit 31d can also maintain the current location's time zone and inherit the previous time zone.

Thereafter, the time adjustment unit 31e adjusts the time based on the information regarding the determined time difference (S33). Through the above steps, the exceptional processing of the time adjustment performed by the satellite radio-controlled wristwatch 1 according to the first and second modified examples is completed.

[Second embodiment]

FIG15 illustrates a first example of a time zone area 70 handled by a satellite radio-controlled watch 1 according to a second embodiment of the present invention. The satellite radio-controlled watch 1 according to the second embodiment differs from the satellite radio-controlled watch 1 according to the first embodiment in the content of the stored time zone/intersection information 32b and the method for determining the time zone. Otherwise, the satellite radio-controlled watch 1 according to the first embodiment and the satellite radio-controlled watch 1 according to the second embodiment have similar structures. The following describes the differences between the satellite radio-controlled watch 1 according to the second embodiment and the satellite radio-controlled watch 1 according to the first embodiment.

The time zone area 70 shown in Figure 15 is the area between 0° and 90° north latitude and E1 and E2 east longitude. In the example shown in this figure, the first reference line 72 intersects the time zone boundary line 71 at latitudes NL1, NL2, NL3, and NL4. Furthermore, the second reference line 73 intersects the time zone boundary line 71 at latitudes NR1, NR2, NR3, and NR4. An intersection at latitude NR1 is considered an adjacent intersection to an intersection at latitude NL1. In this embodiment, ROM 32 stores adjacent intersection information paired with the intersection information as part of the time zone/intersection information 32b. An intersection at latitude NR2 is considered an adjacent intersection to an intersection at latitude NL2, and an intersection at latitude NR3 is considered an adjacent intersection to an intersection at latitude NL3. Similarly, an intersection at latitude NR4 is considered an adjacent intersection to an intersection at latitude NL4. If considering a line segment included in one time difference partition area 70 in the time zone boundary line 71, an intersection point and an adjacent intersection point are points located at both ends of one line segment.

15 shows the current position 76 of the satellite radio-controlled wristwatch 1 indicated by the position information 33a as a triangle. The current position 76 is at north latitude N and east longitude E. The north latitude N is between north latitude NL1 and north latitude NR1.

The time zone zones handled by the satellite radio-controlled watch 1 of this embodiment are wedge-shaped or strip-shaped areas adjacent to the baseline, and are defined by the intersections of the baseline and the time zone boundary lines. Specifically, these zones are designated by a first baseline 72, a second baseline 73, and a line connecting the first and second intersections (the adjacent intersections of the first intersection). An example of a zone zoned for time zone zones is a quadrilateral connecting the points at 0° North Latitude and E1 East, NL1 North Latitude and E1 East, NR1 North Latitude and E2 East, and 0° North Latitude and E2 East. The time zone zone for this zone is "1."

In the example shown in FIG15 , because the current position 76 is within the aforementioned area, the time zone is determined to be "1." On the other hand, when the satellite radio-controlled watch 1 according to the first embodiment of the present invention is at the same location, the time zone is determined to be "0" because the latitude of the current position 76 is greater than the north latitude NL1 and is less than or equal to NL2. However, even in the satellite radio-controlled watch 1 according to the first embodiment, if the width of the time zone area 70 in the longitude direction is sufficiently small (e.g., a width of 1 minute of longitude), the error caused by the inclination of the time zone boundary line 71 relative to the latitude is sufficiently small.

According to the satellite radio-controlled watch 1 of this embodiment, if the time zone boundary line 71 is formed of a straight line, the boundary of the area defining the time zone can be aligned with the time zone boundary line 71. Therefore, in the first embodiment, the longitudinal widths of the time zone regions 70 are all equal (specifically, 1 minute of longitude). However, in this embodiment, the longitudinal widths of the time zone regions 70 can also be varied depending on the location. For example, a reference line can be set at a longitude where the time zone boundary line 71 bends or converges, and linear interpolation can be performed between the intersections of the reference line and the time zone boundary line 71. By adopting this structure, the accuracy of determining the time zone can be maintained with high precision while significantly reducing the storage capacity of the information used to determine the time zone from the location information.

Specifically, the time zone determination in the satellite radio-controlled watch 1 of this embodiment is performed as follows. First, the ratio Z = (E - E1) / (E2 - E1) of the distance along the latitude from the first reference line 72 to the current position 76 to the distance along the latitude from the first reference line 72 to the second reference line 73 is calculated. Next, based on the calculated ratio, the north latitude NM1, the intersection point of the interpolated line connecting the point at north latitude NL1 at east longitude E1 and the point at north latitude NR1 at east longitude E2, and the meridian passing through the current position 76, is determined using the formula NM1 = NL1 + (NR1 - NL1) × Z. Similarly, based on the calculated ratio, the north latitudes NM2, NM3, and NM4, the intersection points of the meridian passing through the current position 76 with the interpolated lines, are determined. The time zone to which the current position 76 belongs is then determined by determining whether the north latitude N of the current position 76 falls between the latitudes NM1, NM2, NM3, and NM4. Furthermore, when the current position's north latitude N coincides with north latitude NM1, for example, the current position 76 can be determined to belong to the time zone south of north latitude NM1. Of course, the current position 76 can also be determined to belong to the time zone north of north latitude NM1.

A specific example of substituting numerical values is as follows. For example, if E1 = 10°00′, E2 = 10°01′, and the east longitude of current location 76 is E = 9°00′, then NM1 = 9°08′30″, NM2 = 27°55′30″, NM3 = 45°49′30″, and NM4 = 64°04′30″ can be calculated. This indicates that the north latitude N = 9°00′ of current location 76 is greater than 0° and less than NM1, and that the time zone for current location 76 is "1."

FIG16 shows the time zone/intersection information 32b stored in the satellite radio-controlled watch 1 according to the second embodiment of the present invention. The ROM 32 of the satellite radio-controlled watch 1 in this embodiment stores, in association with first intersection information indicating the position of a first intersection, namely, the intersection of a first reference line 72 and a time zone boundary line 71, second intersection information (adjacent intersection information) indicating the position of a second intersection, namely, the intersection of a second reference line 73 adjacent to the first reference line 72 and the time zone boundary line 71 (the adjacent intersection of the first intersection). The time zone/intersection information 32b has a data structure that repeatedly stores time zone information, intersection information, and adjacent intersection information. At the starting address 0 of the memory storing the time zone/intersection information 32b, information indicating time zone 1 is stored. The next address stores the latitude of the first intersection, namely, intersection 8°34′ (NL1). The next address stores the latitude of the second intersection, namely, adjacent intersection 9°20′ (NR1) (the latitude of the adjacent intersection relative to the first intersection). By adopting this data structure, the time zone of the quadrilateral area connecting the points at 0° North Latitude and East Longitude E1, 8°34′ North Latitude and East Longitude E1, 9°20′ North Latitude and East Longitude E2, and 0° North Latitude and East Longitude E2 is represented as "1." Furthermore, information about time zone 0 is stored at address 3, followed by information about intersection 28°06′ (NL2) and adjacent intersection 27°52′ (NR2). Thus, the time zone of the quadrilateral area connecting the points at 8°34′ North Latitude and East Longitude E1, 28°06′ North Latitude and East Longitude E1, 27°52′ North Latitude and East Longitude E2, and 9°20′ North Latitude and East Longitude E2 is represented as "0." Information stored after starting address 14 is the time zone information and intersection information for the time zone area located east of second reference line 73. As described above, according to the satellite radio-controlled watch 1 of this embodiment, the area for determining the time zone division can be specified more accurately relative to the time zone boundary line 71 .

Furthermore, the values stored as adjacent intersection information are the values of the intersection information in the adjacent baseline. Therefore, the numbers of the intersections of the second baseline 73 and the time zone boundary line 71 can be stored in the time difference partition/intersection information 32b, respectively, in association with the latitudes of the respective intersections of the first baseline 72 and the time zone boundary line 71. Here, the intersection numbers refer to the numbers indicating the storage order in the intersection information memory. In this embodiment, because the intersection information belonging to the Northern Hemisphere is stored from south to north (and from north to south in the Southern Hemisphere), the intersection numbers refer to the numbers of the intersections counted from latitude 0° to 90° north latitude for each baseline. For example, in the example shown in FIG15 , there are four intersections between the second reference line 73 adjacent to the first reference line 72 and the time zone boundary line 71, which can be referred to as the first intersection (intersection at north latitude NR1), the second intersection (intersection at north latitude NR2), the third intersection (intersection at north latitude NR3), and the fourth intersection (intersection at north latitude NR4) in order from the south. Furthermore, in the time difference zone/intersection information 32 b, the adjacent intersection number “1” may be stored in association with the latitude of the intersection of the first reference line 72 and the time zone boundary line 71, i.e., the intersection at north latitude NL1, the adjacent intersection number “2” may be stored in association with the latitude of the intersection at north latitude NL2, the adjacent intersection number “3” may be stored in association with the latitude of the intersection at north latitude NL3, and the adjacent intersection number “4” may be stored in association with the latitude of the intersection at north latitude NL4. If the numbers of adjacent intersections are known for a given intersection, the latitude of that adjacent intersection can be read, an interpolated line can be calculated, and the time zone of the current location can be determined by comparing it with the latitude of the current location. This data structure further reduces the storage capacity of the information used to determine the time zone from location information, while also allowing for highly accurate time zone determination.

17 shows a second example of time zone divisions 70 handled by the satellite radio-controlled watch 1 according to the second embodiment of the present invention. This figure shows two adjacent time zone divisions 70, with a time zone boundary line 71 partially branching at north latitude NM1.

The satellite radio-controlled watch 1 of this embodiment can uniquely define the time zone divisions even when the time zone boundary line 71 has branch points. In this embodiment, the time zone division/intersection information 32b is paired with adjacent intersection information for each intersection. Therefore, by drawing interpolation lines connecting intersections and adjacent intersections, the time zone divisions can be uniquely specified.

Specifically, in the example shown in FIG17 , among the intersections of first reference line 72 and time zone boundary line 71, the adjacent intersection of the intersection at north latitude NL1 is the intersection at north latitude NM1, the adjacent intersection of the intersection at north latitude NL2 is the intersection at north latitude NM1, and the adjacent intersection of the intersection at north latitude NL3 is the intersection at north latitude NM2. This information is written into the memory area of time difference partition/intersection information 32b, starting from the start address corresponding to time difference partition area 70 on the left side of FIG17 . Furthermore, among the intersections of second reference line 73 and time zone boundary line 71, the adjacent intersection of the intersection at north latitude NM1 is the intersection at north latitude NR1, and the adjacent intersection of the intersection at north latitude NM2 is the intersection at north latitude NR2. The time zone boundary line 71 branches at the intersection point at north latitude NM1, but by storing the intersection point and the adjacent intersection point together, an interpolation line connecting the intersection point and the adjacent intersection point can be uniquely drawn to uniquely specify the area of the time difference partition.

FIG18 shows a third example of a time zone area 70 processed by the satellite radio-controlled watch 1 according to the second embodiment of the present invention. In this example, the time zone boundary line 71 branches from west to east (from left to right in FIG18 ). In this embodiment, to ensure that the interpolation line can be uniquely drawn even in this case, the intersection of the branch points is associated with two pieces of intersection information.

Specifically, in the example shown in Figure 18 , the intersection points of first reference line 72 and time zone boundary line 71 at north latitude NM1 and north latitude NM2 are at the same latitude. In Figure 18 , for simplicity of explanation, the intersection points at north latitude NM1 and north latitude NM2 are staggered, but north latitude NM1 and north latitude NM2 are at the same latitude. The time difference partition/intersection information 32b stores that the adjacent intersection point of the intersection point at north latitude NM1 is the intersection point at north latitude NR1, and the adjacent intersection point of the intersection point at north latitude NM2 is the intersection point at north latitude NR2. In this way, by appropriately increasing the number of intersection points so that intersection points correspond one-to-one with adjacent intersection points, it is possible to uniquely draw interpolation lines connecting the intersection points and adjacent intersection points, thereby uniquely specifying the time difference partition area.

FIG19 is a flowchart illustrating the time adjustment process performed by the satellite radio-controlled watch 1 according to the second embodiment of the present invention. The satellite radio-controlled watch 1 of this embodiment begins the time adjustment process upon user operation of the operating unit 60. First, the watch receives satellite radio signals ( S40 ). Next, the watch obtains the time information and position information contained in the satellite signals and stores them in the RAM 33 ( S41 ).

Next, the time zone determination unit 31a determines whether the latitude of the current location indicated by the acquired location information is greater than or equal to 80° (S42). If the latitude of the current location is not greater than or equal to 80°, it determines to which of the northeast, northwest, southeast, and southwest zones the current location belongs (S43). The longitude of the current location is then rounded off to the nearest second (S44) to determine which time zone the current location belongs to.

After determining the time zone to which the current location belongs, the corresponding starting address is determined (S45). After determining the starting address, the address of the time zone/intersection information 32b to be referenced is determined. Then, based on the intersection information and adjacent intersection information, the interpolation line connecting the intersection and the adjacent intersection is compared with the latitude of the current location (S46). Next, by determining which interpolation line the current location's latitude lies between, the time zone of the current location is determined (S47). Then, referring to the time zone details information 32c, the time zone corresponding to the determined time zone is determined. In addition, the time zone details determination unit 31b determines the details of the time difference such as daylight saving time and city time (S48).

On the other hand, when the latitude of the current position is greater than or equal to 80°, the high latitude processing unit 31d determines the time zone of the current position to be UTC+0 (S49). As described above, the high latitude processing unit 31d may maintain the time zone of the current position and inherit the previous time zone.

After determining the detailed information on the time difference at the current location of the satellite radio-controlled watch 1, the time adjustment unit 31e adjusts the time based on the information on the time difference (S50). The above steps complete the time adjustment process of the satellite radio-controlled watch 1.

FIG20 shows an example of an exception processing range 75 in a satellite radio-controlled watch 1 according to a variation of the second embodiment of the present invention. The time zone division area 70 shown in FIG20 is the same as the time zone division area shown in FIG15 . However, in the satellite radio-controlled watch 1 according to this variation, the exception processing range 75 is set near the time zone boundary by the exception processing range setting unit 31 c.

The exception processing range setting unit 31c of the satellite radio-controlled watch 1 of this embodiment defines a range specified by two adjacent reference lines (a first reference line 72 and a second reference line 73), a line parallel to the line connecting the first and second intersection points (the adjacent intersection points of the first intersection point) and passing through the first intersection point, and a line parallel to the line connecting the first and second intersection points and passing through the second intersection point. Specifically, in the example shown in FIG20 , four exception processing ranges 75 are shown. The southernmost exception processing range 75 is a parallelogram defined by a line (an interpolated line) parallel to the line connecting the intersection point at north latitude NL1 (the first intersection point) and the intersection point at north latitude NR1 (the second intersection point), a line passing through the intersection point at north latitude NL1, and a line parallel to the interpolated line and passing through the intersection point at north latitude NR1. In the example shown in FIG20 , the four exception processing ranges 75 have the same area and the spacing between the parallel lines is the same.

In this variation, after determining the time zone area 70 to which the current position belongs, but before determining the time zone for the current position, the exception range setting unit 31c reads the intersection points and adjacent intersection points belonging to the time zone area 70 and sets an exception range 75. When the position indicated by the position information 33a is within the exception range 75, the time zone determination unit 31a maintains the time zone. The time zone of the satellite radio-controlled watch 1 is maintained when the watch enters the exception range 75 by crossing a line parallel to the interpolation line, and is changed when the watch leaves the exception range 75 by crossing a line parallel to the interpolation line. Setting the exception range 75 as in this variation allows for more accurate setting of the exception range for the time zone boundary line 71, compared to setting the exception range using a reference line or a line of latitude.

The satellite radio-controlled watch 1 of this modification, when performing exceptional time adjustment processing, indicates that the time zone is "NA" by indicating the indefinite processing character 53d with the second hand 52c. This allows the user of the satellite radio-controlled watch 1 to confirm that the time zone is indefinite.

FIG21 is a flowchart illustrating the exceptional processing for time adjustment performed by a satellite radio-controlled watch 1 according to a variation of the second embodiment of the present invention. The satellite radio-controlled watch 1 according to the variation of the second embodiment begins time adjustment processing upon user operation of the operating unit 60. The watch first receives satellite radio signals (S60). The watch then obtains the time information and position information contained in the satellite signals and stores them in RAM 33 (S61).

Next, the time zone determination unit 31a determines whether the latitude of the current location indicated by the acquired location information is greater than or equal to 80° (S62). If the latitude of the current location is not greater than or equal to 80°, it determines to which of the northeast, northwest, southeast, and southwest zones the current location belongs (S63). The longitude of the current location is rounded off to the nearest second (S64) to determine to which time zone the current location belongs.

After determining the time difference partition area to which the current position belongs, the corresponding start address is determined (S65). Thereafter, the exception processing range setting unit 31c reads the intersection information and adjacent intersection information and sets the exception processing range 75 using a line parallel to the interpolation straight line (S66).

Next, a determination is made as to whether the location indicated by the location information 33a is within the exception handling range 75 (S67). If the current location is not within the exception handling range, the time zone/intersection information 32b is referenced using the determined starting address. Based on the intersection information and adjacent intersection information, the interpolated line is compared with the latitude of the current location (S68). The time zone for the current location is determined by determining which interpolated line the latitude of the current location falls between (S69). Next, the time zone corresponding to the determined time zone is determined by referring to the time zone details information 32c. Furthermore, the time zone details determining unit 31b determines details of daylight saving time and other time differences, such as city time (S70).

On the other hand, if the current location is within the exception processing range, the time zone determination unit 31a determines to maintain the time zone (S71). Furthermore, if the current location's latitude is greater than 80°, the high latitude processing unit 31d determines the current location's time zone to be UTC+0 (S72). As previously mentioned, the high latitude processing unit 31d can also maintain the current location's time zone and inherit the previous time zone.

Thereafter, the time adjustment unit 31e adjusts the time based on the information regarding the determined time difference (S73). Through the above steps, the exceptional processing of the time adjustment performed by the satellite radio-controlled wristwatch 1 according to the modification of the second embodiment is completed.

The embodiments of the present invention are not limited to the above-described embodiments. FIG22 is a schematic diagram showing another example of a time zone boundary line 71 and a time difference partition area 70. In this example, the time difference partition area 70 is specified using a reference line along a specific great circle on the earth or a circle parallel to the great circle. Here, the specific great circle is the equator, and the circle parallel to the great circle is the latitude. When specifying the time difference partition area 70 as in this example, if the time difference partition area 70 is specified by, for example, obtaining a reference line every 1 minute in the latitude direction, and storing the intersection information of the latitude and the time zone boundary line 71 and the time difference partition information, then the time difference can also be determined in the same manner as in the previously described embodiment.

Claims (13)

1. A satellite radio-controlled clock, characterized in that it comprises: The receiving unit receives satellite radio waves, including time and location information. The storage unit stores intersection information representing the location of the intersection point of a baseline and a time zone boundary line, and time zone partition information for the region to which the intersection point belongs, which is a wedge-shaped or band-shaped region adjacent to the baseline; the baseline is a meridian orthogonal to the Earth's equator; and The time zone determination unit determines the time zone based on the location information, the intersection information, and the time difference partition information. The baseline intersects the boundary line of the time zone at multiple points. The storage unit stores the latitude information of multiple intersection points of each baseline. The region is defined by two adjacent baselines and a line intersecting the baselines. 2. The satellite radio-controlled clock as described in claim 1, characterized in that: It also has a time difference detail determination unit, which determines daylight saving time and at least one of the cities based on the location information, the intersection information and the time difference partition information. 3. The satellite radio-controlled clock as described in claim 1 or 2, characterized in that: The storage unit stores at least address information and time zone/intersection information. The associated address information includes addresses representing at least one of the time difference partition information and the intersection information according to each of the baselines. The time difference partition/intersection information includes the time difference partition information and the intersection information. The time difference partition information and the intersection information can be viewed based on the address according to the baseline to which each line belongs. 4. The satellite radio-controlled clock as described in claim 3, characterized in that: The storage unit stores adjacent intersection information that is paired with the intersection information. 5. The satellite radio-controlled clock as described in claim 3, characterized in that: The address is the starting address of the time difference partition information and the intersection information of each baseline. The time difference partition/intersection information includes a symbol representing the endpoint of the data belonging to each baseline. 6. The satellite radio-controlled clock as described in claim 1 or 2, characterized in that: The storage unit stores time difference details associated with the time difference partition information. The time difference details include time zone information, and at least one of daylight saving time information and city information. 7. The satellite radio-controlled clock as described in claim 1, characterized in that: It also has an exception handling range setting section. The exception handling range setting unit will include the range of the intersection points, and the range specified by the two adjacent baselines and a line orthogonal to the two baselines separated by a predetermined distance, as the exception handling range. When the location information indicates a location within the exception handling range, the time zone determination unit maintains the time zone. 8. The satellite radio-controlled clock as described in claim 1 or 2, characterized in that: The storage unit stores, in association with first intersection information indicating the position of a first intersection point (the intersection of a first baseline and the boundary line), second intersection information indicating the position of a second intersection point (the intersection of a second baseline adjacent to the first baseline and the boundary line). The region is defined by the first baseline, the second baseline, and the line connecting the first intersection point and the second intersection point. 9. The satellite radio-controlled clock as described in claim 8, characterized in that: It also includes an exception handling range setting unit, which sets a specified area including the intersection point as the exception handling range. When the location information indicates a location within the exception handling range, the time zone determination unit maintains the time zone. 10. The satellite radio-controlled clock as described in claim 9, characterized in that: The exception handling range is defined by the range of two adjacent baselines, a line passing through the first intersection point and orthogonal to the baseline, and a line passing through the second intersection point and orthogonal to the baseline. 11. The satellite radio-controlled clock as described in claim 9, characterized in that: The exception handling range is defined by the two adjacent baselines, the line parallel to the line connecting the first intersection and the second intersection and passing through the first intersection, and the line parallel to the line connecting the first intersection and the second intersection and passing through the second intersection. 12. The satellite radio-controlled clock as described in claim 6, characterized in that: When the time zone information associated with the time zone partition information indicates that the time zone is not specified, the time zone decision unit makes a decision to maintain the time zone or set it to a specific time zone. 13. The satellite radio-controlled clock as described in claim 1 or 2, characterized in that: It also has a high-latitude processing unit, which maintains the time zone or sets it to a specific time zone when the location information indicates a location above a specified latitude.