HK40002852A - Automatic pressure sensor output calibration for reliable altitude determination - Google Patents

Description

Automatic pressure sensor output calibration for reliable absolute altitude determination

The technical field is as follows:

the present disclosure relates to absolute altitude determination for electronic devices using barometric pressure sensors.

Technical background:

the positioning of the electronic device may be achieved using one or more of the following: GNSS satellites, Wi-Fi access points and cellular base stations, and the like. While GNSS can be used to locate outdoor electronic devices in three-dimensional space, indoor three-dimensional positioning presents challenges.

The absolute altitude may be determined by an atmospheric pressure sensor of the electronic device. The absolute altitude is calculated from the difference between the barometric pressure sensor output and the average sea level pressure. Since the barometric pressure sensor of an electronic device is often not calibrated, large deviations in determining the absolute height may occur. For example, different electronic devices containing similar hardware may deviate from each other by an absolute height of 12 meters.

To avoid bias due to an uncalibrated barometric pressure sensor, some electronic devices calculate a relative altitude, which is an absolute altitude difference over a selected period of time or distance. The determination of relative height has limited application due to the dependence on the starting position. For example, the determination of relative height may be used to determine whether a user transporting an electronic device is moving up or down but cannot determine a user floor in a multi-story building unless a starting floor is entered for reference.

Manual calibration of the barometric pressure sensor by the electronic device manufacturer may undesirably extend the production time of the electronic device and the delayed delivery of the electronic device. Manual calibration by the user of the electronic device is inconvenient and may be considered cumbersome, especially if the use of the electronic device is restricted before the calibration is complete.

To summarize:

according to an aspect of the present disclosure, there is provided a method of calibrating an output of an absolute barometric pressure sensor of an electronic device, comprising: determining, by a processor of the electronic device, that the location of the electronic device is at a known absolute altitude and outdoors; the processor receives a measured pressure from the absolute barometric pressure sensor; calculating in a processor a difference between the measured pressure and a reference pressure, the reference pressure determined by adjusting an average sea level pressure based on the known absolute height relative to an average sea level at the location of the electronic device; storing the difference in a memory of the electronic device; and applying the difference to the output of the absolute barometric pressure sensor; wherein determining that the electronic device is at a known absolute height and outdoors occurs without user input.

According to another aspect of the present disclosure, there is provided an electronic device including: an absolute barometric pressure sensor for generating an output indicative of an absolute altitude of the electronic device; and a processor in communication with the motion sensor and the GNSS subsystem for determining that the location of the electronic device is at a known absolute altitude and outdoors; the processor: the method includes receiving a measured pressure from an absolute barometric pressure sensor, calculating a difference between the measured pressure and a reference pressure, storing the difference in a memory of an electronic device in communication with a processor, and applying the difference to an output of the absolute barometric pressure sensor, the reference voltage determined by adjusting an average sea level pressure based on the known absolute altitude relative to an average sea level at a location of the electronic device.

According to another aspect of the present disclosure, there is provided a method of calibrating an output of an absolute barometric pressure sensor of an electronic device, comprising: determining, at a processor of the electronic device, that the location of the electronic device is at ground level when the first criterion and the second criterion satisfy a threshold time period; the processor receives a measured pressure from the absolute barometric pressure sensor; a processor calculates a difference between the measured pressure and a reference pressure, the reference voltage determined by adjusting an average sea level pressure based on the known absolute height relative to an average sea level at the location of the electronic device; storing the difference in a memory of the electronic device; and applies the difference to the output of the absolute barometric pressure sensor.

According to still another aspect of the present disclosure, there is provided an electronic device including: an absolute barometric pressure sensor for generating an output indicative of an absolute altitude of the electronic device; and a processor in communication with the motion sensor and the GNSS subsystem, for determining that the location of the electronic device is at ground level when the first criterion and the second criterion satisfy a threshold time period, the processor, after determining that the location of the electronic device is at ground level: receiving measured pressures from an absolute horizontal pressure and a reference pressure, storing the difference in a memory of an electronic device in communication with the processor, and applying the difference to an output of an absolute barometric pressure sensor, the reference voltage determined by adjusting an average sea level pressure based on the known absolute altitude relative to an average sea level at the location of the electronic device.

The attached drawings are as follows:

examples are given in the following figures, in which like reference numerals refer to like parts. The present disclosure is not limited to the embodiments shown in the drawings.

Fig. 1 is a block diagram of an electronic device for implementing the barometric pressure sensor calibration method according to the present disclosure.

FIG. 2 is a flow diagram of a method of calibrating an atmospheric pressure sensor according to one embodiment.

FIG. 3 is a graph of an output pattern of one embodiment of a motion sensor according to the electronic device of FIG. 1.

FIG. 4 is one embodiment of a signal-to-noise ratio (SNR) plot of GNSS signals received at the electronic device of FIG. 1.

FIG. 5 is a flow diagram according to one embodiment of a method of determining that a user is at ground level and outdoors.

Fig. 6 and 7 are schematic diagrams showing consumer electronics located at ground level and in a building, respectively.

Detailed description:

it will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the examples described herein. However, it will be understood by those of ordinary skill in the art that the examples described herein may be practiced without these specific details. Unless explicitly stated, the methods described herein are not limited to a particular order or sequence. Additionally, some of the described methods or elements thereof may occur or be performed at the same point in time. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the embodiments described herein. Moreover, this description is not to be taken as limiting the scope of the embodiments described herein.

Referring to FIG. 1, one embodiment of an electronic device 10, the electronic device 10 includes a main processor subsystem 16 that controls overall operation thereof. The main processor subsystem 16 includes a processor 18, a memory 20, and a communication interface 22. One embodiment of the main processor subsystem 16 is a Single Board Computer (SBC) having an Operating System (OS).

The communication interface 22 enables communication with the server 30 via a wireless or wired connection. The server 30 may be a single server or a group of servers in communication with each other. The electronic device 10 may additionally or alternatively communicate directly with another electronic device. In one embodiment, the electronic device 10 communicates with a navigation system of the vehicle through a communication interface 22.

The electronic device 10 includes a GNSS antenna 28 for receiving GNSS signals and a GNSS subsystem 12 in communication with the main processor subsystem 16 and the GNSS antenna 28. The GNSS subsystem 12 may be operable to generate digitized GNSS data corresponding to the GNSS signals for further processing by the main processor subsystem 16. Embodiments of the GNSS subsystem 12 include: a standalone GNSS receiver capable of producing a local position estimate, an assisted GNSS (A-GNSS) receiver that receives assistance data from another device to provide a position estimate, a Radio Frequency (RF) Front End (FE) associated with a Software Defined Radio (SDR) receiver at the electronic device 10 or distributed on one or more servers 30.

The barometric pressure sensor 24 communicates with the main processor subsystem 16 to send barometric pressure sensor output thereto. Barometric pressure sensor 24 may be any sensor capable of outputting an indication of absolute barometric pressure at the location of electronic device 10.

The motion sensor 26 communicates with the main processor subsystem 16 to send motion sensor output thereto. The motion sensor 26 may be an accelerometer, gyroscope, magnetometer, or other type of sensor capable of detecting motion of the electronic device 10.

The electronic device 10 is powered by a power supply 32, and the power supply 32 communicates with the main processor subsystem 16 through the power interface 14. In one embodiment, the power source 32 is one or more batteries. In another embodiment, power source 32 is a power source of a vehicle in which electronic device 10 is installed.

For example, the electronic device 10 may be a smartphone, a tablet, a laptop, an activity tracking device, a beacon, a router, a machine-to-machine (M2M) device, or a vehicle navigation system. The electronic device 10 includes an output device 34 to indicate to a user the absolute height of the electronic device 10. For example, the absolute height of the output may be a distance above or below ground level or a number of floors when the user of the delivery electronic device 10 is in a building. The output devices 34 communicate with the main processor subsystem 16 and may be, for example, one or more of a display, speakers, and other output devices. The electronic device 10 may further include an input device 36 in communication with the main processor subsystem 16 to receive user input.

Referring to fig. 2, a method of calibrating an output of an electronic device absolute barometric pressure sensor, comprising: at 40, the processor 18 determines that the location of the electronic device 10 is at ground level and outdoors, and at 42, the processor 18 receives the measured pressure (P) from the absolute barometric pressure sensor 24_SENSOR) At 44, the processor 18 calculates the difference (P) between the measured pressure and the reference pressure_REFERENCE) The reference pressure is determined by adjusting the average sea level pressure based on the ground level height relative to the average sea level at the location of the electronic device 10, storing the difference in the memory 20 of the electronic device 10 at 46, and applying the difference to the output of the absolute barometric pressure sensor 24 at 48.

As will be understood by those skilled in the art, the difference may be a positive value added to the subsequently measured pressure or a negative value added to the subsequently measured pressure.

Periodically updated average sea level pressures are available to various weather service providers around the world, such as custom weather inc. The frequency of the average sea level pressure update and the granularity of the area to which the average sea level pressure applies may be selected to achieve accuracy requirements and data transfer loads.

The ground level height relative to the average sea level varies depending on where the electronic device 10 is located in the world. The absolute altitude is determined from a topographic map that provides the absolute altitude of the average sea level relative to different locations in the world. The terrain maps may be obtained from many different sources, including government agencies (e.g., the terrain information center in canada). On-line topographic information resources (e.g., from Google)^TMThe resources of the map) are also available.

The average sea level pressure is adjusted according to the absolute height of the ground level to determine P by mathematical methods well known to those skilled in the art_REFERENCE. In one example, the determined absolute height of the ground plane is further adjusted by 1 meter in order to position the electronic device, for example, relative to the userIs substantially horizontal.

At 44, prior to calculating the difference, the electronic device 10 determines at 40 that the user transporting the electronic device 10 is at ground level and outdoors. In one embodiment, user input is relied upon to determine when the electronic device 10 is located at ground level and outdoors. For example, user input may be received in response to a query generated by processor 18 or in response to a user selecting an atmospheric pressure sensor calibration option via a user interface of electronic device 10.

Other example methods disclosed herein automatically determine that the electronic device 10 is at ground level and outdoors. Automatic determination of outdoor and ground level locations can be performed without user input and without making the user aware that a determination is being made. Electronic device users can enter and exit buildings and above and below ground all day long. The indoor user may be at any height relative to the ground level. This is also true for outdoor users. A user with gait-type movement may travel indoors or outdoors. When a user transporting the electronic device 10 travels in gait motion for a relatively long time, it can be determined that the user is outdoors and at ground level. When the first criterion and the second criterion satisfy the threshold time period, the location of the electronic device may be determined to be outdoors and at ground level.

The first criterion is met when the output from the motion sensor 26 indicates that the motion of the user transporting the device corresponds to the selected type of motion. The processor 18 determines whether the sensor output corresponds to the selected type of motion by matching the motion sensor output pattern to a known motion sensor output pattern. For example, the motion sensor output pattern may correspond to a gait of the user when the user transporting the electronic device 10 is walking or running. Referring to fig. 3, one embodiment of an accelerometer output pattern corresponding to a walking gait is shown. Other known motion sensor output patterns are also possible, for example, a sensor output pattern corresponding to a user transporting the electronic device 10 in a pocket while riding a bicycle. In general, the output from motion sensor 26 may match any known motion sensor output pattern from which it may be determined that electronic device 10 is at ground level.

The first criterion is satisfied when the output from the motion sensor 26 indicates that the motion of the user of the transport apparatus corresponds to the selected type of motion. The first criterion may alternatively be satisfied when the output from the GNSS subsystem 12 indicates that the motion of the electronic device 10 corresponds to the selected type of motion. In this embodiment, the movement of the electronic device 10 may be indicated in dependence of a difference in GNSS position of the electronic device 10 over a period of time. Walking can be determined when a speed of about 4km/h is determined. Similarly, when determining a speed of 30km/h or higher, it may be determined that the electronic device 10 is traveling in a vehicle such as an automobile, for example. When determining a speed indicative of a mode of transportation, a cycling or other mode of transportation may be determined. In embodiments where electronic device 10 is in communication with the electronic system of the vehicle, the first criterion may also be satisfied when the vehicle's transportation of electronic device 10 is determined based on, for example, the output of the vehicle's odometer. Similar to the embodiment of the GNSS, when a speed of 30km/h or higher is determined, it is determined that the electronic device 10 is traveling in a vehicle.

The selected type of motion is stored in the memory 20 of the main processor subsystem 16 and compared to one or more of the following: a motion sensor output, a GNSS based motion determination and an odometer based motion determination to determine whether a first criterion is met. According to one embodiment, determining the selected type of motion determined from the motion sensor output using the GNSS output may be performed. In this embodiment, when the sensor output pattern corresponds to a selected type of motion over a period of time, the GNSS output may be used to confirm that the corresponding expected distance has been traveled over the period of time. By using the GNSS output to confirm the selected type of motion determined by the motion sensor output, errors due to special situations, such as a user transporting the electronic device 10 around a roof track or on a treadmill, are avoided. Other validation checks may also be performed.

The second criterion is met when a signal-to-noise ratio (SNR) of the GNSS signals received at the electronic device 10 is above a threshold. The second criterion is not met if no GNSS signals are received at the electronic device 10, for example when the electronic device 10 is indoors. In one embodiment, the threshold is between 34dB and 35 dB. In another embodiment, the threshold is about 34 dB. Referring to fig. 4, an embodiment of the signal-to-noise ratio of GNSS signals received as an electronic device is time-varying.

One embodiment of a method of determining that a user-transported electronic device is at ground level and outdoors is shown in fig. 5. At 50, a timer is started. At 52, data indicative of the motion of the electronic device, such as motion sensor output, GNSS position data or odometer data, is collected, and at 56, SNR data for the GNSS signals is collected. At 54, the processor 18 of the electronic device 10 determines whether the first criterion has been met by determining whether the collected data corresponds to the selected type of motion. If not, the time is restarted and further motion sensor data collected at 50. At 58, the processor 18 of the electronic device 10 determines whether the second criterion has been met by determining whether the SNR data of the GNSS signals received at the electronic device 10 is above a threshold. If not, the time is restarted at 50 and further more SNR data for the GNSS signals is collected. At 60, if both criteria are met, it is determined whether a threshold time period has been exceeded. If so, the electronic device 10 is determined to be at ground level 62. If not, data indicative of device motion and SNR data for the GNSS signals continues to be collected at 52 and 56, respectively.

The threshold time period for which the first and second criteria are met in order to determine that the electronic device 10 is at ground level is between 2 and 30 minutes. In one embodiment, the threshold time period is about five minutes. Lower or higher threshold time periods are also possible.

According to one embodiment, an error indication associated therewith may be provided to a calibrated absolute barometric pressure sensor output. In this embodiment, the second criterion and the threshold time period comprise an error indication which may be combined to indicate an error in the calibrated barometric pressure sensor output. For example, SNRs below a threshold may be collected in fig. 5 and used to calculate differences in the method of fig. 2. The amount by which the SNR is below the threshold is then used to generate an indication of error. The electronic device 10 then outputs the height ± error. The error may be increased or decreased based on the time at which the first and second criteria are met. As will be appreciated by those skilled in the art, the output is more reliable if the time substantially exceeds the threshold time period. Similarly, if the time is less than the threshold time period, the output is less reliable.

The method of calibrating an atmospheric pressure sensor disclosed herein operates automatically such that a user of the electronic device 10 may not know that calibration is in progress. The method may be run continuously (continuously) in order to increase the reliability of the calculated difference. In this embodiment, the current difference (which may also be referred to as the current offset) of the barometric pressure sensor stored in memory 20 of electronic device 10 is replaced when a new difference is calculated that has a smaller error associated with it.

The method of calibrating the barometric pressure sensor may be performed by the main processor subsystem 16 of the electronic device 10 by executing one or more software applications stored as computer readable code in the memory 20. Alternatively, the method may be performed by dedicated hardware (e.g., an Application Specific Integrated Circuit (ASIC) or a Graphics Processing Unit (GPU)) of the main processor subsystem 16, e.g., by a combination of hardware and software. Optionally, portions of the method may be performed at one or more remote servers in communication with the electronic device 10.

The method may be performed entirely on the electronic device 10. In this embodiment, the average sea level pressure and the topographic map are downloaded to the electronic device 10 and the calculations are performed locally. In another embodiment, the average sea level pressure and the topographic map may be selectively stored at the server 30 and transmitted to the electronic device 10 in response to a request including the location of the electronic device 10. The method may then be performed locally. Alternatively, the method may be performed at the server 30 in response to a request from the electronic device 10, the request including the location of the electronic device 10 and the locally measured ground level pressure output from the absolute barometric pressure sensor.

The calibration output from the barometric pressure sensor is used to determine the absolute altitude of the electronic device 10. Fig. 6 shows a user carrying the electronic device 10 on a ground plane. Figure 7 shows a user located on the floor 4 of a building. Because the barometric pressure sensor 24 of the electronic device 10 carried by the user is calibrated according to the methods disclosed herein, the electronic device 10 is able to determine on which floor the user is when the user is in the building. An uncalibrated barometric pressure sensor may result in absolute altitude measurements up to 3 floors from the user's actual location, as shown by the user carrying electronic devices 10' and 10 ", which are shown on floors 1 and 7, respectively, of the building.

In another embodiment, the electronic device 10 automatically determines that the user transporting the electronic device 10 is at a known absolute altitude, such as ground level and outdoors, in response to the occurrence of an event. For example, the event may be a communication between the electronic device 10 and a beacon of an outdoor nearby network. In this embodiment, the beacons of the proximity network have known absolute heights, and the reference pressure (P) is determined by adjusting the average sea level pressure based on the absolute height of the average sea level at the location relative to the electronic device_REFERENCE). For example, communication between the beacon and the electronic device 10 may occur during a point-of-sale transaction or when the electronic device 10 receives a beacon broadcast from a nearby beacon.

In general, any method of automatically determining that the user transporting the electronic device 10 is at a known absolute height (e.g., ground level) and outdoors may be used. For example, an accurate two-dimensional GPS location of the electronic device 10 in combination with an accurate map including the architectural structure may be sufficient to provide confirmation that the electronic device 10 is at a known absolute height and outdoors.

As will be appreciated by those skilled in the art, outdoors may include covered outdoor locations, indoor locations adjacent to an open window or other indoor type locations where an atmospheric pressure sensor can indicate outdoor pressure.

The method described herein compensates for variability in the barometric pressure sensor output of the electronic device 10. By calibrating the barometric pressure sensor output, the absolute altitude determination of the electronic device is more likely to be accurate. Automatic calibration of the barometric pressure sensor output is convenient because calibration occurs without input from the user. Furthermore, it improves the reliability of the barometric pressure sensor output from the electronic device 10, since non-calibration, e.g. due to the user forgetting to start calibration, is avoided.

The methods disclosed herein are globally applicable. Calibration may be performed at any location in the world where current average sea level pressure and topographical information is available. Further, the altitude determined using the calibrated barometric pressure sensor output is an absolute altitude. Thus, the altitude determined by the electronic device 10 may be combined with other positioning systems to provide the location of the electronic device 10 in indoor and outdoor three-dimensional spaces.

Specific examples have been shown and described herein. However, modifications and variations will occur to those skilled in the art. All such modifications and variations are considered to be within the scope and range of the present disclosure.

Claims (20)

1. A method of calibrating an absolute barometric pressure sensor output of an electronic device, comprising:

determining, by a processor of an electronic device, that a location of the electronic device is at a known absolute altitude and outdoors;

the processor receiving a measured pressure from an absolute barometric pressure sensor;

the processor calculating a difference between the measured pressure and a reference pressure, the reference pressure determined by adjusting an average sea level pressure based on the known absolute height relative to an average sea level at the electronic device location;

storing the difference in a memory of the electronic device; and

applying the difference to an output of an absolute barometric pressure sensor;

wherein the location of the electronic device at a known absolute height and outdoors is determined without user input.

2. The method of claim 1, wherein the determining that the location of the electronic device is at a known absolute altitude and outdoors occurs in response to an event.

3. The method of claim 2, wherein the event is a beacon communication with a neighboring network, the beacon being located at the known absolute altitude and outdoors.

4. The method of claim 1, wherein the known absolute altitude is a ground level, and wherein the location of the electronic device is determined to be at the ground level and outdoors when the first criterion and the second criterion satisfy a threshold time period.

5. The method of claim 4, wherein the first criteria is motion sensor data corresponding to a selected type of motion, the selected type of motion comprising walking or running of a user transporting the electronic device.

6. The method of claim 4, wherein the first criterion is a GNSS output indicative of a travel speed of the electronic device.

7. The method of claim 4, wherein the second criterion is a signal-to-noise ratio (SNR) of GNSS signals received at the electronic device being above a threshold.

8. The method of claim 1, wherein the known absolute altitude is a ground level and determining that the location of the electronic device is outside of the ground level comprises:

receiving, by a processor of the electronic device, motion sensor data of the electronic device, the motion sensor data indicating a selected type of motion of a user within a threshold time period; and

a GNSS subsystem of the electronic device in communication with the processor receives GNSS signals and determines that a signal-to-noise ratio (SNR) of the GNSS signals is above a threshold during the threshold time period.

9. The method of claim 8, wherein the selected type of motion is walking or running of a user transporting the electronic device.

10. The method of claim 8, wherein the threshold time period is between 2 minutes and 30 minutes.

11. The method of claim 8, wherein the threshold period of time is about 5 minutes.

12. The method of claim 8, wherein the threshold is approximately 34 dB.

13. A non-transitory computer-readable medium having computer-readable code stored thereon, the computer-readable code being executable by at least one processor of the electronic device to perform the method of claim 1.

14. An electronic device, comprising:

an absolute barometric pressure sensor for generating an output indicative of an absolute altitude of the electronic device; and

a processor in communication with a motion sensor and a GNSS subsystem to determine that a position of the electronic device is at a known absolute altitude and outdoors, the processor: receiving a measured pressure from the absolute barometric pressure sensor, calculating a difference between the measured pressure and a reference pressure, storing the difference in a memory of the electronic device in communication with the processor, and applying the difference to an output of the absolute barometric pressure sensor, the reference pressure determined by adjusting an average sea level pressure based on the known absolute altitude relative to an average sea level at the location of the electronic device.

15. The electronic device of claim 14, wherein the known absolute altitude is a ground level, and wherein the location of the electronic device is determined to be at ground level and outdoors when the first criterion and the second criterion satisfy the threshold time period.

16. The electronic device of claim 15, wherein the first criteria is motion sensor data corresponding to a selected type of motion, the selected type of motion comprising walking or running of a user transporting the electronic device.

17. The electronic device of claim 15, wherein the first criterion is a GNSS output indicative of a travel speed of the electronic device.

18. The electronic device of claim 15, wherein the second criterion is a signal-to-noise ratio (SNR) of GNSS signals received at the electronic device being above a threshold.

19. The electronic device of claim 15, wherein the threshold period of time is approximately 5 minutes.

20. The electronic device of claim 18, wherein the threshold is approximately 34 dB.