WO2018142408A1

WO2018142408A1 - Navigation systems and methods

Info

Publication number: WO2018142408A1
Application number: PCT/IL2018/050119
Authority: WO
Inventors: Hanoch Cohen
Original assignee: Israel Aerospace Industries Ltd
Current assignee: Israel Aerospace Industries Ltd
Priority date: 2017-02-05
Filing date: 2018-02-04
Publication date: 2018-08-09
Anticipated expiration: 2019-08-05
Also published as: IL250459B1; IL250459A0; IL250459B2

Abstract

A navigation device is configured to communicate with at least one first device comprising a first clock with a first clock bias and configured to receive first signals from at least a first localization network, the navigation device comprising at least a second clock with a second clock bias, at least a receiver configured to receive second signals from a second localization network, and at least a signal generator synchronized with the second clock, and configured to generate a synchronization signal and send it to said first device, wherein data representative of reception of the synchronization signal by the first device provides information on a relationship between the first clock bias and the second clock bias, for calculating navigation data of the first device based at least on the first signals, the second signals and said relationship.

Description

NAVIGATION SYSTEMS AND METHODS

TECHNICAL FIELD

The presently disclosed subject matter relates to a solution for determining navigation data.

BACKGROUND

In the prior art, it is known to determine navigation data (such as position data) of a device based on signals received from a localization network (such as GPS signals).

There is now a need to propose new methods and systems for determining navigation data.

GENERAL DESCRIPTION

In accordance with certain aspects of the presently disclosed subject matter, there is provided a navigation device, configured to communicate with at least one first device comprising a first clock with a first clock bias and configured to receive first signals from at least a first localization network, the navigation device comprising at least a second clock with a second clock bias, at least a receiver configured to receive second signals from a second localization network, and at least a signal generator synchronized with the second clock, and configured to generate a synchronization signal and send it to said first device, wherein data representative of reception of the synchronization signal by the first device provides information on a relationship between the first clock bias and the second clock bias, for calculating navigation data of the first device based at least on the first signals, the second signals and said relationship.

According to some embodiments, the navigation data are calculated by a processing unit of the navigation device, or by a processing unit of the first device, or by a processing unit in communication with the navigation device and/or the first device. According to some embodiments, the navigation device and the first device are located at the same position, or at a distance less than a predefined threshold, or at a known distance. According to some embodiments, the navigation data comprise at least two position data, and the first signals are provided by two emitters of the first localization network and the second signals are provided by at least one emitter of the second localization network, or the first signals are provided by one emitter of the first localization network and the second signals are provided by at least two emitters of the second localization network. According to some embodiments, the navigation data comprise at least three position data, and the first signals are provided by three emitters of the first localization network and the second signals are provided by at least one emitter of the second localization network, or the first signals are provided by two emitters of the first localization network and the second signals are provided by at least two emitters of the second localization network, or the first signals are provided by one emitter of the first localization network and the second signals are provided by at least three emitters of the second localization network. According to some embodiments, the navigation device comprises a frequency analyser, configured to measure the frequency of a signal produced by the first device, and a processing unit configured to determine, based at least on the measurement provided by the frequency analyser, a relationship between a first clock drift of the first clock and a second clock drift of the second clock. According to some embodiments, the processing unit is configured to calculate navigation data of the first device based at least on the first signals, the second signals, and the relationship between the first clock drift of the first clock and the second clock drift of the second clock. According to some embodiments, the processing unit is configured to calculate navigation data of the first device at first period of time based at least on the first signals, the second signals, and the relationship between the first clock bias and the second clock bias, and calculate navigation data of the first device at a second period of time based at least on the first signals, the second signals, and the relationship between the first clock drift of the first clock and the second clock drift of the second clock.

These embodiments can be combined according to any of their possible technical combination.

In accordance with some aspects of the presently disclosed subject matter, there is provided a navigation system comprising at least one first device comprising a first clock with a first clock bias, and at least a receiver configured to receive first signals from at least a first localization network, a navigation device comprising at least a second clock with a second clock bias, at least a receiver configured to receive second signals from a second localization network, and at least a signal generator synchronized with the second clock, and configured to generate a synchronization signal and send it to said first device, wherein the navigation system is configured, by a processing unit to calculate a relationship between the first clock bias and the second clock bias based on data representative of the reception of the synchronization signal by the first device, for calculating navigation data of the first device based at least on the first signals, the second signals and said relationship.

According to some embodiments, the navigation system is further configured to calculate navigation data of the first device based at least on the first signals, the second signals and said relationship. According to some embodiments, the navigation device and the first device are located at the same position, or at a distance less than a predefined threshold, or at a known distance. According to some embodiments, the navigation device is in compliance with at least some of the embodiments described above.

In accordance with some aspects of the presently disclosed subject matter, there is provided a navigation device, configured to communicate with at least one first device comprising a first clock with a first clock drift, and configured to receive first signals from at least a first localization network, the navigation device comprising at least a second clock with a second clock drift, at least a receiver configured to receive second signals from a second localization network, and at least a frequency analyser, configured to measure the frequency of a signal produced by the first device, and a processing unit configured to determine, based at least on the measurement provided by the frequency analyser, a first relationship between the first clock drift and the second clock drift, for determining navigation data of the first device based at least on the first signals, the second signals and said first relationship.

According to some embodiments, the processing unit is configured to receive data indicative of a relationship between a first clock bias of the first clock and a second clock bias of the second clock at an initial time. According to some embodiments, the navigation data comprise at least two position data, and the first signals are provided by two emitters of the first localization network and the second signals are provided by at least one emitter of the second localization network, or the first signals are provided by one emitter of the first localization network and the second signals are provided by at least two emitters of the second localization network. According to some embodiments, the navigation data comprise at least three position data, and the first signals are provided by three emitters of the first localization network and the second signals are provided by at least one emitter of the second localization network, or the first signals are provided by two emitters of the first localization network and the second signals are provided by at least two emitters of the second localization network, or the first signals are provided by one emitter of the first localization network and the second signals are provided by at least three emitters of the second localization network. According to some embodiments, the navigation device comprises at least a signal generator synchronized with the second clock, and configured to generate a synchronization signal and send it to said first device, wherein data representative of the reception of the synchronization signal by the first device provides information on a second relationship between a first clock bias of the first clock and a second clock bias of the second clock, for calculating navigation data of the first device based at least on the first signals, the second signals, said first relationship and/or said second relationship.

In accordance with some aspects of the presently disclosed subject matter, there is provided a navigation system comprising at least one first device comprising a first clock with a first clock drift, and at least a receiver configured to receive first signals from at least a first localization network, a navigation device comprising at least a second clock with a second clock drift, at least a receiver configured to receive second signals from a second localization network, and at least a frequency analyser, configured to measure the frequency of a signal produced by the first device, and a processing unit configured to determine, based at least on the measurement provided by the frequency analyser, a first relationship between the first clock drift and the second clock drift, for determining navigation data of the first device based at least on the first signals, the second signals and said first relationship. According to some embodiments, the navigation device and the first device are located at the same position, or at a distance less than a predefined threshold, or at a known distance. According to some embodiments, the navigation device is in compliance with at least some of the embodiments described above.

In accordance with some aspects of the presently disclosed subject matter, there is provided a device comprising a processing unit, and a first clock with a first clock bias, and wherein the device is configured to receive first signals from at least a first localization network, and to communicate with a navigation device comprising at least a second clock with a second clock bias, at least a receiver configured to receive second signals from a second localization network, and at least a signal generator synchronized with the second clock, and configured to generate a synchronization signal and send it to said device, wherein the processing unit is configured to determine a relationship between the first clock bias and the second clock bias based at least on data representative of the reception of the synchronization signal by the device, for calculating navigation data of the device based at least on the first signals, the second signals and said relationship.

In accordance with some aspects of the presently disclosed subject matter, there is provided a device comprising a processing unit, and a first clock with a first clock drift, and wherein the device is configured to receive first signals from at least a first localization network, and to communicate with a navigation device comprising at least a second clock with a second clock drift, at least a receiver configured to receive second signals from a second localization network, and at least a frequency analyser, configured to measure the frequency of a signal produced by the device, and wherein the processing unit is configured to determine, based at least on the measurement provided by the frequency analyser, a first relationship between the first clock drift and the second clock drift, for determining navigation data of the first device based at least on the first signals, the second signals and said first relationship.

According to some embodiments, the navigation device and the first device are located at the same position, or at a distance less than a predefined threshold, or at a known distance. According to some embodiments, the navigation device is in compliance with at least some of the embodiments described above.

In accordance with some aspects of the presently disclosed subject matter, there is provided a method of determining navigation data of a first device comprising a first clock with a first clock bias and configured to receive first signals from at least a first localization network, the method comprising generating a synchronization signal with a signal generator of a navigation device, said navigation device comprising a second clock with a second clock bias and being configured to receive second signals from a second localization network, wherein the signal generator is synchronized with the second clock, sending said synchronization signal to the first device, determining, based on data representative of the reception of the synchronization signal by the first device, a relationship between the first clock bias and the second clock bias, for calculating navigation data of the first device based at least on the first signals, the second signals and said relationship.

According to some embodiments, the navigation data comprise at least two position data, and the first signals are provided by two emitters of the first localization network and the second signals are provided by at least one emitter of the second localization network, or the first signals are provided by one emitter of the first localization network and the second signals are provided by at least two emitters of the second localization network. According to some embodiments, the navigation data comprise at least three position data, and the first signals are provided by three emitters of the first localization network and the second signals are provided by at least one emitter of the second localization network, or the first signals are provided by two emitters of the first localization network and the second signals are provided by at least two emitters of the second localization network, or the first signals are provided by one emitter of the first localization network and the second signals are provided by at least three emitters of the second localization network. According to some embodiments, the method further comprises measuring, by a frequency analyser, the frequency of a signal produced by the first device, and determining, based at least on the measurement provided by the frequency analyser, a relationship between a first clock drift of the first clock and a second clock drift of the second clock. According to some embodiments, the method comprises determining navigation data of the first device based at least on the first signals, the second signals, and the relationship between the first clock drift of the first clock and the second clock drift of the second clock. According to some embodiments, the method comprises determining navigation data of the first device at a first period of time based at least on the first signals, the second signals, and the relationship between the first clock bias and the second clock bias, and determining navigation data of the first device at a second period of time based at least on the first signals, the second signals, and the relationship between the first clock drift of the first clock and the second clock drift of the second clock.

In accordance with some aspects of the presently disclosed subject matter, there is provided a method of determining navigation data of a first device comprising a first clock with a first clock drift and configured to receive first signals from at least a first localization network, the method comprising measuring, by a frequency analyser of a navigation device comprising a second clock drift and being configured to receive second signals from a second localization network, a signal produced by the first device, and determining, based at least on the measurement provided by the frequency analyser, a first relationship between the first clock drift and the second clock drift, for determining navigation data of the first device based at least on the first signals, the second signals and said first relationship.

According to some embodiments, the navigation device comprises at least a signal generator synchronized with the second clock, and is configured to generate a synchronization signal and send it to said first device, and the method comprises determining, based on data representative of the reception of the synchronization signal by the first device, information on a second relationship between a first clock bias and a second clock bias, for calculating navigation data of the first device based at least on the first signals, the second signals, said first relationship and/or said second relationship. According to some embodiments, the navigation data are determined by a processing unit of the device or of the navigation device.

In accordance with some aspects of the presently disclosed subject matter, there is provided a non-transitory storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method of determining navigation data of a first device comprising a first clock with a first clock bias and configured to receive first signals from at least a first localization network, the method comprising instructing a signal generator of a navigation device to generate a synchronization signal, said navigation device comprising a second clock with a second clock bias and being configured to receive second signals from a second localization network, wherein the signal generator is synchronized with the second clock, instructing the navigation device to send said synchronization signal to the first device, determining, based on data representative of the reception of the synchronization signal by the first device, a relationship between the first clock bias and the second clock bias, for calculating navigation data of the first device based at least on the first signals, the second signals and said relationship.

In accordance with some aspects of the presently disclosed subject matter, there is provided a non-transitory storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method of determining navigation data of a first device comprising a first clock with a first clock drift and configured to receive first signals from at least a first localization network, the method comprising instructing a frequency analyser of a navigation device to measure the frequency of a signal produced by the first device, wherein the navigation device comprises a second clock drift and is configured to receive second signals from a second localization network, and determining, based at least on the measurement provided by the frequency analyser, a first relationship between the first clock drift and the second clock drift, for determining navigation data of the first device based at least on the first signals, the second signals and said first relationship.

According to some embodiments, the proposed solution provides a navigation system which is able to benefit from signals emitted by multiple localization systems.

According to some embodiments, the proposed solution enables a low cost device to benefit from precise navigation data.

According to some embodiments, the proposed solution maintains the calculation of navigation data of a device even if some of the emitters of the localization system, with which the device is configured communicate, are not operable.

According to some embodiments, the proposed solution offers a more reliable and precise navigation solution.

According to some embodiments, the proposed solution can be beneficial for reducing power consumption.

According to some embodiments, the proposed solution can be used for determining navigation data of existing devices, even if it is not possible or if it is not desired to change the configuration of these existing devices.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it can be carried out in practice, embodiments will be described, by way of non-limiting examples, with reference to the accompanying drawings, in which:

- Fig. 1 illustrates a device in communication with a localization network;

- Fig. 2 illustrates an embodiment in which a navigation device is configured to communicate with the device of Fig. 1;

- Fig. 3 illustrates an embodiment of a method of determining navigation data of the device; - Fig. 4 illustrates an embodiment of a method of determining a relationship between the first clock bias and the second clock bias;

- Fig. 5 illustrates an embodiment of a system which can be used for determining navigation data of the device;

- Fig.6 illustrates an embodiment of a method of determining navigation data of the device;

- Fig. 7 illustrates another embodiment in which a navigation device can be configured to communicate with the device of Fig. 1;

- Fig. 8 illustrates another embodiment of a method of determining navigation data of the device;

- Fig. 9 illustrates another embodiment in which a navigation device can be configured to communicate with the device of Fig. 1;

- Fig. 10 illustrates another method of determining navigation data of the device.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the presently disclosed subject matter may be practiced without these specific details. In other instances, well-known methods have not been described in detail so as not to obscure the presently disclosed subject matter.

Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as "sending", "determining", "calculating", "receiving", "instructing" or the like, refer to the action(s) and/or processes) of a processor that manipulate and/or transform data into other data, said data represented as physical, such as electronic, quantities and/or said data representing the physical objects.

The term "processing unit" covers any computing unit or electronic unit that may perform tasks based on instructions stored in a memory, such as a computer, a server, a chip, a processor, etc. It encompasses a single processor or multiple processors, which may be located in the same geographical zone or may, at least partially, be located in different zones and may be able to communicate together. The term "non-transitory memory" as used herein should be expansively construed to cover any volatile or non-volatile computer memory suitable to the presently disclosed subject matter.

Embodiments of the presently disclosed subject matter are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the presently disclosed subject matter as described herein.

Fig. 1 represents a device 100 comprising a processing unit 101 and a first clock 103. The first clock 103 has a first clock bias CBi.

The clock bias of a clock can be due e.g. to delays introduced by electronics present in the clock and/or in the device, and/or by delays introduced by the clock and/or by uncertainties on parameters of the components of the device and/or of the clock.

According to some embodiments, the first clock bias CBi(t) can be expressed as such:

In this formula, CBi(to) is the first clock bias at an initial time to and CDi is the first clock drift of the first clock 103.

This formula is a possible way to model the first clock bias but other models can be used.

The device 100 further comprises a communication unit 104, for receiving (and, if necessary, sending) data. The communication unit 104 can comprise e.g. an antenna.

The device 100 can be configured to receive first signals from a plurality of emitters 106 (in some embodiments, these emitters can also receive data) of at least a first localization network 105. The first localization network 105 can be for example a GNSS network (such as the GPS network), or a cellular network (e.g. 3G/4G). Other localization networks can be used. The signals provided by the localization networks can be e.g. RF signals.

A localization network can include a network of emitters which provide a signal or a plurality of signals to a device, for determining the position of the device based on said signals.

Thus, the first signals can be used by the device 100 to determine its navigation data (such as position data, inertial data, velocity data, etc.). Fig. 2 illustrates an embodiment in which a navigation device 250 is configured to communicate with the device (reference number 200 in Fig.2).

The communication unit 204, the processing unit 201 and the first clock 203 can be similar to what was described with reference to Fig. 1.

The communication of data between the device 200 and the navigation device 250 can be performed e.g. through wireless communication (using known wireless communication protocols, such as Bluetooth, Wi-Fi, etc.) and/or through a physical link (see communication link depicted as reference 260 in Fig. 2).

The device 200 can be configured to receive first signals from emitters) 206 of a first localization network 205.

The navigation device 250 can comprise a processing unit 251 and at least a second clock 252 with a second clock bias CB₂. According to some embodiments, the second clock bias CB₂(t) can be expressed as such:

CB₂(t)= CB₂(to) + CD₂.t

In this formula, CB₂(to) is the second clock bias at an initial time to and CEh is the second clock drift of the second clock 252.

This formula is one possible way to model the second clock bias, but other models can be used.

The navigation device 250 can further comprise a communication unit 254, for receiving (and, if necessary, sending) data. The communication unit 254 can comprise e.g. an antenna.

The navigation device 250 can be configured to receive second signals from emitters) 256 (if necessary, these emitters can also receive data) of at least a second localization network 255. The second localization network 255 can be for example a GNSS network (such as the GPS network), or a cellular network (e.g. 3G/4G). Other localization networks can be used.

These second signals can be used by the navigation device 250 to determine its navigation data (such as position data, etc.).

Generally, the second localization network 255 is different from the first localization network 205.

In some embodiments, the first localization network can rely on a first technological solution such as GNSS, and the second localization network can rely on a second technological solution such as 3G. In other embodiments, the first and the second localization networks can rely on similar technological solutions but provided by different networks. For example, the first localization network can be GPS and the second localization network can be Glonass. These examples are however not limitative.

According to some embodiments, the second localization network 255 is synchronized (time synchronization) with the first localization network 205.

According to some embodiments, the device and the navigation device are located in the same physical device. In this case, the navigation device and the device are located at the same position (or the distance between them can be approximated as being equal to zero).

According to some embodiments, at least part of the components of the device and of the navigation device are located on the same chip.

According to other embodiments, the navigation device and the device are located at a distance less than a predefined threshold.

According to other embodiments, the navigation device and the device are located at a known distance. According to some embodiments, their relative orientation can also be known in advance.

The value of the distance between the navigation device and the device can be stored in non-transitory memory of the navigation device and/or of the device, or in an external non-transitory memory in communication with the navigation device and/or the device.

These different configurations can apply to the embodiment of Fig. 2 and also to the other embodiments described later in the present specification.

As shown in Fig. 2, the navigation device 250 can further comprise a signal generator 257. The signal generator 257 can generate a synchronization signal (or a plurality of synchronization signals) which can be communicated to the device 200. According to some embodiments, the synchronization signal can be, a similar or identical signal to the signals of the emitters of the first localization network.

For example, if the first localization network is a GNSS network such as a GPS network, the signal generator can comprise e.g. a GPS simulator which generates a GPS signal. Similarly, if the first localization network is a 3G network, the signal generator can comprise e.g. a simulator of a 3G emitter in order to provide a synchronization signal corresponding to a 3G signal. These examples are however not limitative. The signal generator 257 can be synchronized with the second clock 252.

According to some embodiments, the device 200 is configured to add (through an adapted multiplexer or a signal addition device) this synchronization signal to the first signals received from the first localization network 205.

Attention is now drawn to Fig. 3, which illustrates a method of determining navigation data of the device based on the system described in Fig.2.

The method can comprise a step 300 of generating a synchronization signal with the signal generator, wherein the signal generator is synchronized with the second clock.

The method can comprise a step 301 of sending the synchronization signal to the device through a communication link (see reference 260 in Fig. 2).

The method can comprise a step 302 of detemiining, based on data representative of the reception of the synchronization signal by the device, a relationship between the first clock bias CBi and the second clock bias CB₂.

Step 302 can be performed e.g. by the processing unit of the device 200, or by another processing unit in communication with the device 200 (which can be a remote processing unit), or by the processing unit of the navigation device 250 or by the conjunction of a plurality of these processing units.

A non-limiting example of the determination of a relationship between the first clock bias and the second clock bias is provided with reference tofig.4.

As mentioned with reference to step 300 of Fig. 3, the signal generator generates a synchronization signal which is sent by the navigation device 450 at time Ts, and received by the device 400 at time TR. The distance between the device 400 and the navigation device 450 is "d".

As a consequence, the following relationship can be written:

Generally, the distance d is negligible or equal to zero. We thus obtain:

Ts and TR are known data, thus it is possible to determine at each time a relationship between the first clock bias CBi and the second clock bias CB₂.

According to some embodiments, the relationship can be calculated and updated at several time instants.

The update frequency can be e.g. predefined and if necessary can evolve. The processing unit which determines the navigation data can e.g. control this update frequency. This relationship can be used for determining navigation data of the device, as explained with reference to Fig.5 and Fig.6.

As shown in Fig. 5, the device 500 receives first signals from three emitters 506 of a first localization network 505. The unknown data of the device 500 comprise three position data (x , y, z) of the device and the first clock bias CB i of the first clock.

As explained later in the specification, a different number of emitters and signals than the embodiment depicted in Fig. 5 can be used to determine navigation data of the device 500.

In order to determine these four unknown data, at least four signals from four emitters would be needed.

According to some embodiments, signals received by the navigation device from an emitter of the second localization network can be also used to solve the four unknown data (as depicted in Fig. 5, the device 500 and the navigation device 550 can exchange data through the communication link 560).

Indeed, as shown in Fig. 5, the navigation device 550 receives second signals from at least one emitter 556 of the second localization network 555.

As mentioned above, according to some embodiments, the position of the navigation device 550 is either equal (or approximated as equal) to the position of the device 500, and thus does not introduce additional unknown data. According to some embodiments, the position of the navigation device 550 with respect to the device 500 is known. Thus, the position of the navigation device 550 is not an additional unknown data either.

However, the clock bias CB-> of the navigation device 550 is also unknown. As explained with reference to Figs. 3 and 4, it is possible to obtain a relationship between the first clock bias CBi and the second clock bias CB₂.

As a consequence, only four unknown data are to be determined:

- (x, y, z), which correspond to the position data of the device 500 (if it is known in advance that the device is located on the ground, the variable z is not unknown and is equal to zero);

- Clock bias CBi (since CB₂ can been expressed as a function of CBi).

Thus, localization signals from four emitters are sufficient to solve the four unknown data.

In the non-limiting embodiment of Fig. 5, signals are received from three emitters of the first localization network and from one emitter of the second localization network. This is however not limitative and a different number of signals can be used from each localization network.

Some principles that can be used for determination of the navigation data (such as position data) of the device are briefly described here, based on the non-limiting embodiment of Fig, 5. It is understood that other techniques and other principles can be used to solve the unknown data based on signals received from the first localization network, the second localization network, and the relationship between the first clock bias and the second clock bias.

The device 500 can receive at time TRH a signal emitted at time TEU by the emitter li of the first localization network (where i is equal to 1, 2 or 3). Thus, the following equations can be written (for i equal to 1, 2 or 3):

In this equation, Rn is the distance between the device and the emitter li, c is the speed of light, and CBi is the clock bias of the first clock of the device 500.

Similar equations can be written for the navigation device 550 with respect to the second localization network 555. The navigation device 550 can receive at time T

signals emitted at time by the emitter 2i of the second localization network (where i

is equal to 1 in the embodiment of Fig.5).

Thus, the following equation can be written (for i equal to 1):

In this equation, R_2i is the distance between the navigation device 550 and the emitter 2i, c is the speed of light, and CB₂ is the clock bias of the second clock of the navigation device 550.

As explained with reference e.g. to Figs. 3 and 4, it is possible to express CB₂ as a function (e.g. a function f) of CBi.

In addition, according to some embodiments, the navigation device 550 and the device 500 have the same position (or approximately the same position), or the distance between them is known (in this case it is possible to express R^ as a function "g" of Rn, wherein "g" depends on the distance "d").

Thus, the above mentioned equation can be reformulated as following (for i equal to 1, and in the case where Ra and Rn are approximated as equal):

The position data of the device 500 (which can be deduced from Rli) can thus be calculated based on the first signals provided by the first localization network, the second signals provided by the second localization network, and the relationship between the first clock bias and the second clock bias (function f). If necessary, the distance between the device and the navigation device can also be taken into account if it is not a negligible value (as explained above).

It is to be noted that a different number of signals provided by emitters of the localization networks can be used than in the embodiment depicted in Fig.5.

According to some embodiments, the navigation data mat are to be calculated comprise at least two position data (such as x and y), and:

- the first signals are provided by two emitters of the first localization network and the second signals are provided by at least one emitter of the second localization network, or

- the first signals are provided by one emitter of the first localization network and the second signals are provided by at least two emitters of the second localization network.

According to other embodiments, the navigation data comprise at least three position data (such as x, y, and z), and:

- the first signals are provided by three emitters of the first localization network and the second signals are provided by at least one emitter of the second localization network, or

- the first signals are provided by two emitters of the first localization network and the second signals are provided by at least two emitters of the second localization network, or

- the first signals are provided by one emitter of the first localization network and the second signals are provided by at least three emitters of the second localization network.

It is to be understood that if N unknown data are to be determined, and signals are available from more than N emitters (over the two localization networks), determination of the unknown data can a fortiori be performed (since the number of signals exceeds the number of unknown data).

A method of determining navigation data of the device is illustrated in Fig.6, which can rely on the various embodiments described above. The method can comprise:

- a step 600 of generating a synchronization signal (this step is similar to step 300 of Fig.3), - a step 601 of sending the synchronization signal to the device (this step is similar to step 301 of Fig.3),

- a step 602 of determining a relationship between the first clock bias and the second clock bias (this step is similar to step 301 of Fig. 3).

The method can further comprise a step 603 of determining navigation data of the device based at least on the first signals received by the device from the first localization network, the second signals received by the navigation device from the second localization network, and the relationship between the first clock bias and the second clock bias.

Step 603 can be performed e.g. by the processing unit of the device 500. In mis case, the navigation device can communicate to the device 500 data related to the second signals that it has received from the second localization network (such as time Ύκα and time TEX mentioned in the equation above).

According to some embodiments, determination of the navigation data can be performed by the processing unit of the device in conjunction with the processing unit of the navigation device.

According to some embodiments, determination of the navigation data can be performed by another processing unit (which can be external, e.g. located in a central station), in communication with the device and the navigation device.

According to some embodiments, determination of the navigation data can be performed by the processing unit of the navigation device. In this case, the device can communicate the calculated relationship (between the first clock bias and the second clock bias) and data related to the first signals (such as time TRH and time TEU mentioned in the equation above) to the navigation device.

Attention is now drawn to Fig. 7. In this embodiment, the device 700 can comprise a communication unit 704, a processing unit 701 and a first clock 703. The navigation device 750 can comprise a communication unit 754, a processing unit 751 and a second clock 752.

As mentioned with respect to Fig. 2, the device 700 can receive first signals from a first localization network 705, and the navigation device 750 can receive second signals from a second localization network 755.

In addition, the navigation device 750 can comprise a frequency analyser 758 (or spectrum analyser). A frequency analyser can provide an analysis or a representation of the frequencies present in an electronic signal. The frequency analyser 758 can communicate with the device through a wired connection, and/or through a wireless connection. For example, an electromagnetic radiation produced by the device can be sensed by a sensor of the navigation device, which can be e.g. an antenna or the communication unit of the navigation device. The sensed signal can men be communicated to the frequency analyser.

In particular, according to some embodiments, the frequency analyser 758 can measure the frequency of a signal produced by the device. The signal produced by the device can be a signal produced (intentionally or unintentionally) by a component of the device which is synchronized and/or connected to the first clock 703. For example, the signal can be produced by the processing unit 701, or by the communication unit 704, or by the first clock 703. These examples are however not limitative.

According to some embodiments, the frequency analyser 758 is connected to at least one component of the device, in order to measure the frequency of the signals produced by this component.

According to some embodiments, a radiation produced by the device is sensed by the navigation unit (such as by the communication unit 754) and transmitted to the frequency analyser 758 for measuring its frequency.

In some embodiments, the navigation device can further comprise a filter in order to select, in this radiation, a signal to be analysed by the frequency analyser.

According to some embodiments, the frequency analyser 758 can be connected to an input of the device 700, in particular to the input of the device 700 at which the first signals are received from the first localization network 705.

A coupler can be used at the input of the device 700 in order to connect the device 700 to the frequency analyser 758.

The frequency analyser 758 can be synchronized with the second clock 752.

The measurement provided by the frequency analyser 758 is representative of a relationship between the first clock drift CDi of the first clock and the second clock drift CD₂ of the second clock.

Indeed, according to some embodiments, the signal S produced by the device (such as by a component of the device which is synchronized with the first clock or connected to the first clock) can be modelled as following:

In this formula, N and M ate pre-known constants of the device (which can be obtained e.g. by testing the device), Fi is the frequency of the first clock, and CDi is the first clock drift.

The frequency analyser 758 can measure the frequency of the signal S, and provides a frequency measurement MES which can be modelled as following:

In this formula, P, Q are pre-known constants (these constants can depend e.g. on the frequency analyser 758, and on the frequency of the second clock), and CD₂ is the second clock drift.

Since N, M, P, Q and Fi are known, it is thus possible to obtain, based on the measurement M provided by the frequency analyser 758, a relationship between the first clock drift CDi of the first clock and the second clock drift CI¾, which can be expressed e.g. as following:

A processing unit can determine this relationship based at least on the measurement MES and the different parameters mentioned above.

The relationship between the first clock drift CDi of the first clock and the second clock drift CD₂ can be used to calculate a relationship between the first clock bias CBi and CB₂.

Indeed, the following equation can be written:

In this equation, to is an initial time.

According to some embodiments, the expression "CB₂(to) - CBi(to)" can be calculated at an instant in which four emitters (or three emitters if only two position data are unknown) are available for the device in the first localization network and four emitters (or three emitters if only two position data are unknown) are available for the navigation device in the second localization network. In this case, CB₂(to) can be calculated and CBi(to) can be calculated (e.g. respectively by the processing unit of the device and of the navigation device).

According to some embodiments, the expression "CB₂(to) - CBi(to)" can be calculated using the method described with reference e.g. to Figs. 3 and 4, which can provide a relationship between the first clock bias and the second clock bias at each instant of time. In this case, the navigation device can comprise both a signal generator and a frequency analyser, wherein the signal generator can be used to calculate the relationship between the first clock bias and the second clock bias at an initial time, and the frequency analyser can be used to calculate the relationship between the first clock drift and the second clock drift in a subsequent period of time (see e.g. Fig. 10 for a possible corresponding embodiment).

A method of determining navigation data of the device is illustrated in Fig. 8, which can rely e.g. on the system described with reference to Fig. 7. The method can comprise:

- a step 800 of measuring, by a frequency analyser, the frequency of a signal produced by the device (the measurement provided by the frequency analyser can be representative of a relationship between the first clock drift and the second clock drift, and can be based e.g. on the measurement of the frequency of a signal produced by a component of the device which is synchronized with the first clock or connected to the first clock), and

- a step 801 of determining a relationship between the first clock drift and the second clock drift (see e.g. equation 3 above) based at least on this measurement.

The method can further comprise a step 802 of determining navigation data of the device based at least on the first signals received by the device from the first localization network, the second signals received by the navigation device from the second localization network, and the relationship between the first clock drift and the second clock drift.

In order to determine navigation data, similar principles and equations to those described with reference to the embodiments of Figs. 2 to 6 can be used. Thus, these principles and equations are not repeated.

As mentioned above (see equation 4), in some embodiments, a relationship between the first clock bias and the second clock bias can be calculated at an initial period of time (such as when sufficient coverage is provided by the emitters of the first and second localization networks), wherein this relationship can be used, in conjunction with the relationship between the first clock drift and the second clock drift, for determining the relationship between the first clock bias and the second clock bias during time. The relationship between the first clock bias and the second clock bias can be used in equations 1 , 2 and 2' to determine position data of the device, as explained e.g. in the embodiment described with respect to Figs.2 to 6.

Steps 801 and/or 802 can be performed e.g. by the processing unit of the device 700. In this case, the navigation device 750 can communicate to the device 700 data related to the second signals that it has received from the second localization network (such as time and time mentioned in the equations 1, 2 and 2' above).

According to some embodiments, determination of the navigation data can be performed by the processing unit of the navigation device. In this case, the device can communicate the calculated relationship (between the first clock drift and the second clock drift) and data related to the first signals (such as time TRU and time TEH mentioned in the equation above) to the navigation device.

A different number of signals/emitters can be used than in the embodiment depicted in Fig.7.

According to other embodiments, the navigation data comprise at least three position data (such as x, y and z), and:

- the first signals are provided by three emitters of the first localization network and the second signals are provided by at least one emitter of the second localization network, or - the first signals are provided by two emitters of the first localization network and the second signals are provided by at least two emitters of the second localization network, or

It is to be understood that if N unknown data are to be determined, and signals are available from more man N emitters (over the two localization networks), determination of the unknown data can a fortiori be performed.

Attention is now drawn to Fig. 9. In this embodiment, the device 900 can comprise a communication unit 904, a processing unit 901 and a first clock 903. Hie navigation device 950 can comprise a communication unit 954, a processing unit 951, a second clock 952, a signal generator 957 (similar to signal generator 257) synchronized with the second clock 952 and a frequency analyser 958 (similar to a frequency analyser 758) also synchronized with the second clock 952.

The frequency analyser 958 can communicate with the device 900 (as mentioned with reference to Fig. 7, this communication can be wired or wireless), in order to measure the frequency of a signal produced by the device (such as a signal produced by a component synchronized with first clock 903 and/or connected to the first clock 903).

Fig. 10 illustrates a navigation method which can rely on the system described with reference to Fig.9.

The method can comprise a step 1000 of generating a synchronization signal with the signal generator 957. This step is similar to step 600.

The method can comprise a step 1001 of sending the synchronization signal to the device. This step is similar to step 601.

The method can comprise a step 102 of determining a first relationship between the first clock bias and the second clock bias. This step is similar to step 602. For example, the first relationship can be established for an initial time to, which thus provides a relationship between CBi(to) and CB2(to). This is however not mandatory and this relationship can be established at a subsequent time.

If necessary, the method can comprise at tins stage calculating navigation data of the device, as explained with reference to step 602 of Fig.6.

The method can comprise a step 1003 of measuring, by the frequency analyser, a signal produced by the device. This step is similar to step 800. The method can comprise a step 1004 of determining a second relationship between the first clock drift and the second clock drift based at least on the measurement provided by the frequency analyser. This step is similar to step 801.

The method can then comprise a step 1005 of calculating navigation data based on the first signals, the second signals, and the second relationship between the first clock drift of the first clock and the second clock drift of the second clock.

According to some embodiments, the following equation can be used to calculate the relationship between the first clock bias and the second clock bias at each time t.

The expression can be e.g. obtained at step 1002.

According to some embodiments, the method can comprise iterating steps 1003 to 1005, without necessarily iterating steps 1000 to 1002.

For example, during a first period of time, the method can rely, for determining the navigation data, on the signals obtained from the first localization network, the signals obtained from the second localization network, and the first relationship between the first clock bias and the second clock bias calculated using the synchronization signal, and during a second period of time, the method can rely, for determining the navigation data, on the signals obtained from the first localization network, the signals obtained from the second localization network, and the second relationship between the first clock drift and the second clock drift calculated using the measurement provided by the frequency analyser.

According to some embodiments, in case of deficiency of the signal generator, the frequency analyser can be used to calculate the navigation data, or in case of deficiency of the frequency analyser, the signal generator can be used to calculate the navigation data.

According to some embodiments, both the signals provided by the signal generator and the frequency analyser can be used to calculate the navigation data. In mis case, a processing unit (of the device, or of the navigation device, or an external processing unit) can aggregate the navigation data calculated using the signal generator and the navigation data calculated using the frequency analyser, in order to determine the navigation data (the aggregation can be based e.g. on an average).

According to some embodiments, in order to determine navigation data of the device, a processing unit (of the device, or of the navigation device, or an external processing unit) can choose to use: - for a period of time, only the frequency analyser,

- for another period of time, only the signal generator,

- for another period of time, both the frequency analyser and the signal generator.

In at least some of the embodiments described above, the device is a component that cannot be modified. In other embodiments, the device could theoretically be modified but it is not desired to modify this component In other embodiments, the hardware of the device cannot be modified (or it is not desired to modify the hardware) but a software can be stored in a non-transitory memory of the device. By causing the navigation device to communicate with the device (according to the various embodiments described above), it is possible to determine navigation data of the device without modifying said device, or without substantially modifying the device.

The invention contemplates a computer program being readable by a computer for executing one or more methods of the invention. The invention further contemplates a machine-readable memory tangibly embodying a program of instructions executable by the machine for executing one or more methods of the invention.

It is to be noted that the various features described in the various embodiments may be combined according to all possible technical combinations.

It is to be understood that the invention is not limited in its application to the details set forth in the description contained herein or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Hence, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures, methods, and systems for carrying out the several purposes of the presently disclosed subject matter.

Those skilled in the art will readily appreciate that various modifications and changes can be applied to the embodiments of the invention as hereinbefore described without departing from its scope, defined in and by the appended claims.

Claims

1. A navigation device, configured to communicate with at least one first device comprising a first clock with a first clock bias and configured to receive first signals from at least a first localization network, the navigation device comprising:

- at least a second clock with a second clock bias,

- at least a receiver configured to receive second signals from a second localization network, and

- at least a signal generator

o synchronized with the second clock, and

o configured to generate a synchronization signal and send it to said first device,

wherein data representative of reception of the synchronization signal by the first device provides information on a relationship between the first clock bias and the second clock bias, for calculating navigation data of the first device based at least on the first signals, the second signals and said relationship.

2. The navigation device of claim 1, wherein the navigation data are calculated by a processing unit of the navigation device, or by a processing unit of the first device, or by a processing unit in communication with the navigation device and/or the first device.

3. The navigation device of any of claims 1 or 2, wherein the navigation device and the first device are located at the same position, or at a distance less man a predefined threshold, or at a known distance.

4. The navigation device of any of claims 1 to 3, wherein the navigation data comprise at least two position data, and

5. The navigation device of any of claims 1 to 3, wherein the navigation data comprise at least three position data, and - the first signals are provided by three emitters of the first localization network and the second signals are provided by at least one emitter of the second localization network, or

6. The navigation device of any of claims 1 to S, further comprising:

- a frequency analyser, configured to measure the frequency of a signal produced by the first device, and

- a processing unit configured to determine, based at least on the measurement provided by the frequency analyser, a relationship between a first clock drift of the first clock and a second clock drift of the second clock.

7. The navigation device of claim 6, wherein the processing unit is configured to calculate navigation data of the first device based at least on:

- the first signals,

- the second signals, and

- the relationship between the first clock drift of the first clock and the second clock drift of the second clock.

8. The navigation device of any of claims 6 or 7, wherein the processing unit is configured to:

- calculate navigation data of the first device at first period of time based at least on:

o the first signals,

o the second signals, and

o the relationship between the first clock bias and the second clock bias, and

- calculate navigation data of the first device at a second period of time based at least on:

o the first signals,

o the second signals, and o the relationship between the first clock drift of the first clock and the second clock drift of the second clock.

9. A navigation system comprising:

- at least one first device

o comprising a first clock with a first clock bias, and o at least a receiver configured to receive first signals from at least a first localization network,

- a navigation device comprising

o at least a second clock with a second clock bias,

o at least a receiver configured to receive second signals from a second localization network, and

o at least a signal generator

^■ synchronized with the second clock, and

^■ configured to generate a synchronization signal and send it to said first device,

wherein the navigation system is configured, by a processing unit:

- to calculate a relationship between the first clock bias and the second clock bias based on data representative of the reception of the synchronization signal by the first device, for calculating navigation data of the first device based at least on die first signals, the second signals and said relationship.

10. Hie navigation system of claim 9, further configured to calculate navigation data of the first device based at least on the first signals, the second signals and said relationship.

11. The navigation system of any of claims 9 or 10, wherein the navigation device and the first device are located at the same position, or at a distance less than a predefined threshold, or at a known distance.

12. The navigation system of any of claims 9 to 11, wherein the navigation device is in compliance with any of claims 4 to 8.

13. A navigation device, configured to communicate with at least one first device comprising a first clock with a first clock drift, and configured to receive first signals from at least a first localization network, the navigation device comprising:

- at least a second clock with a second clock drift,

- at least a receiver configured to receive second signals from a second localization network, and - at least a frequency analyser, configured to measure the frequency of a signal produced by the first device, and

- a processing unit configured to:

o determine, based at least on the measurement provided by the frequency analyser, a first relationship between the first clock drift and the second clock drift, for determining navigation data of the first device based at least on the first signals, the second signals and said first relationship.

14. The navigation device of claim 13, wherein the processing unit is configured to receive data indicative of a relationship between a first clock bias of the first clock and a second clock bias of the second clock at an initial time.

15. The navigation device of any of claims 13 or 14, wherein the navigation data comprise at least two position data, and

16. The navigation device of any of claims 13 or 14, wherein the navigation data comprise at least three position data, and

17. The navigation device of any of claims 13 to 16, further comprising:

- at least a signal generator

o synchronized with the second clock, and o configured to generate a synchronization signal and send it to said first device,

wherein data representative of the reception of the synchronization signal by the first device provides information on a second relationship between a first clock bias of the first clock and a second clock bias of the second clock, for calculating navigation data of the first device based at least on the first signals, the second signals, said first relationship and/or said second relationship.

18. A navigation system comprising:

- at least one first device

o comprising a first clock with a first clock drift, and o at least a receiver configured to receive first signals from at least a first localization network,

- a navigation device comprising

o at least a second clock with a second clock drift,

o at least a frequency analyser, configured to measure the frequency of a signal produced by the first device, and

- a processing unit configured to:

19. The navigation system of claim 18, wherein the navigation device and the first device are located at the same position, or at a distance less than a predefined threshold, or at a known distance.

20. The navigation system of any of claims 18 or 19, wherein the navigation device is in compliance with any of claims 14 to 17.

21. A device comprising:

- a processing unit, and

- a first clock with a first clock bias, and

wherein the device is configured to receive first signals from at least a first localization network, and to communicate with a navigation device comprising: - at least a second clock with a second clock bias,

- at least a signal generator

o synchronized with the second clock, and

o configured to generate a synchronization signal and send it to said device,

wherein the processing unit is configured to determine a relationship between the first clock bias and the second clock bias based at least on data representative of the reception of the synchronization signal by the device, for calculating navigation data of the device based at least on the first signals, the second signals and said relationship.

22. A device comprising

- a processing unit, and

- a first clock with a first clock drift, and

wherein the device is configured to receive first signals from at least a first localization network, and to communicate with a navigation device comprising:

- at least a second clock with a second clock drift,

- at least a frequency analyser, configured to measure the frequency of a signal produced by the device, and

wherein the processing unit is configured to determine, based at least on the measurement provided by the frequency analyser, a first relationship between the first clock drift and the second clock drift, for determining navigation data of the first device based at least on the first signals, the second signals and said first relationship.

23. A method of determining navigation data of a first device comprising a first clock with a first clock bias and configured to receive first signals from at least a first localization network, the method comprising:

- generating a synchronization signal with a signal generator of a navigation device, said navigation device comprising a second clock with a second clock bias and being configured to receive second signals from a second localization network, wherein the signal generator is synchronized with the second clock,

- sending said synchronization signal to the first device, - determining, based on data representative of the reception of the synchronization signal by the first device, a relationship between the first clock bias and the second clock bias, for calculating navigation data of the first device based at least on the first signals, the second signals and said relationship.

24. The method of claim 23, wherein the navigation data comprise at least two position data, and

- the first signals are provided by one emitter of the first localization network and the second signals are provided by at least two emitters of the second localization network

25. The method of claim 23, wherein the navigation data comprise at least three position data, and

26. The method of any of claims 23 to 25, further comprising:

- measuring, by a frequency analyser, the frequency of a signal produced by the first device, and

- deterrnining, based at least on the measurement provided by the frequency analyser, a relationship between a first clock drift of the first clock and a second clock drift of the second clock.

27. The method of claim 26, comprising determining navigation data of the first device based at least on:

- the first signals,

- the second signals, and - the relationship between the first clock drift of the first clock and the second clock drift of the second clock.

28. The method of any of claims 26 or 27, comprising:

- determining navigation data of the first device at a first period of time based at least on:

o the first signals,

o the second signals, and

o the relationship between the first clock bias and the second clock bias, and

- determining navigation data of the first device at a second period of time based at least on:

o the first signals,

o the second signals, and

o the relationship between the first clock drift of the first clock and the second clock drift of the second clock.

29. A method of determining navigation data of a first device comprising a first clock with a first clock drift and configured to receive first signals from at least a first localization network, the method comprising:

- measuring, by a frequency analyser of a navigation device comprising a second clock drift and being configured to receive second signals from a second localization network, a signal produced by the first device, and

- determining, based at least on the measurement provided by the frequency analyser, a first relationship between the first clock drift and the second clock drift, for determining navigation data of the first device based at least on the first signals, the second signals and said first relationship.

30. The method of claim 29, wherein the navigation device comprises at least a signal generator synchronized with the second clock, and is configured to generate a synchronization signal and send it to said first device, the method comprising:

- determining, based on data representative of the reception of the synchronization signal by the first device, information on a second relationship between a first clock bias and a second clock bias, for calculating navigation data of the first device based at least on the first signals, the second signals, said first relationship and/or said second relationship.

31. Hie method of any of claims 29 or 30, wherein the navigation data are determined by a processing unit of the device or of the navigation device.

32. A non-transitory storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method of determining navigation data of a first device comprising a first clock with a first clock bias and configured to receive first signals from at least a first localization network, the method comprising:

- instructing a signal generator of a navigation device to generate a synchronization signal, said navigation device comprising a second clock with a second clock bias and being configured to receive second signals from a second localization network, wherein the signal generator is synchronized with the second clock,

- instructing the navigation device to send said synchronization signal to the first device,

- determining, based on data representative of the reception of the synchronization signal by the first device, a relationship between the first clock bias and the second clock bias, for calculating navigation data of the first device based at least on the first signals, the second signals and said relationship.

33. A non-transitory storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method of cLetermining navigation data of a first device comprising a first clock with a first clock drift and configured to receive first signals from at least a first localization network, the method comprising:

- instructing a frequency analyser of a navigation device to measure the frequency of a signal produced by the first device, wherein the navigation device comprises a second clock drift and is configured to receive second signals from a second localization network, and - determining, based at least on the measurement provided by the frequency analyser, a first relationship between the first clock drift and the second clock drift, for determining navigation data of the first device based at least on the first signals, the second signals and said first relationship.