PROXIMITY-BASED NAVIGATION METHOD

Abstract

A method for improving accuracy of a raw GPS positioning of an untargeted pedestrian device wherein the pedestrian device receives from a nearby vehicle device a message containing a calculated offset between a raw GPS location of the vehicle and a corrected location of the vehicle, the message being received as a direct consequence of the pedestrian device and the vehicle device coming into mutual communication range without a need for pairing between the two devices. The calculated offset is applied to the raw GPS positioning of the pedestrian device to obtain a more accurate location of the pedestrian device.

Claims

1. A method for improving accuracy of a raw GPS positioning of an untargeted pedestrian device, the method comprising: (a) the pedestrian device receiving from a nearby vehicle device in Bluetooth™ communication range a message containing a calculated offset between a raw GPS location of the vehicle and a corrected location of the vehicle, the message being a popup notification that encapsulates the calculated offset and is received without a need for pairing between the two devices; (b) the pedestrian device ensuring that the vehicle is within a sufficiently narrow range of the pedestrian device that the received offset is applicable to the pedestrian device either by employing a Bluetooth™ protocol that permits mutual communication only within said narrow range or by relating only to signals from a passing vehicle whose measured signal strength exceeds a predetermined threshold; (c) the pedestrian device decoding said message to extract the calculated offset; and (d) applying the calculated offset to the raw GPS positioning of the pedestrian device so as to obtain a more accurate location of the pedestrian device.

2. The method according to claim 1, wherein the message is transmitted by the vehicle using Bluetooth™ as a response to a Bluetooth™ enquiry sent by the pedestrian device.

3. The method according to claim 2, wherein the calculated offset is contained in a Bluetooth™ Description Field of the message.

4. The method according to claim 2, wherein the vehicle device is configured to: (a) obtain a coarse location of the vehicle; (b) obtain a corrected location of the vehicle; (c) compute the offset; and (d) encode the offset in the Bluetooth™ Description Field message of the vehicle device for decoding by the pedestrian device when in communication range of the vehicle device.

5. The method according to claim 1, wherein the message is transmitted by the vehicle using Bluetooth™ Low Energy (BLE) Advertising.

6. The method according to claim 5, wherein the vehicle device is configured to: (a) obtain a coarse location of the vehicle; (b) obtain a corrected location of the vehicle; (c) compute the offset; and (d) encode the offset in a BLE beacon message broadcast by the vehicle device for detection by the pedestrian device when in broadcast range of the vehicle device.

7. The method according to claim 1, further including the following operations carried out by the pedestrian device: (a) receiving multiple respective signals from different vehicles in communication range of the pedestrian, each signal containing a respective offset {ΔX, ΔY}; (b) for each received signal determining a respective signal intensity (Received Signal Strength Indication, RSSI); and (c) using the respective offset {ΔX, ΔY} from whichever of said signals has maximal RSSI.

8. The method according to claim 1 for allowing a vehicle to locate a pedestrian, the method further including: (a) receiving from the pedestrian device a corrected location; and (b) locating the pedestrian based on the received corrected location.

9. The method according to claim 1, wherein at least one of the pedestrian device and the vehicle device filters out fluctuating satellite signals by: (a) receiving from at least four satellites respective GPS signals identifying time of transmission; (b) determining a time of receipt of said GPS signals; (c) computing an effective time of transit and a pseudo-range between the satellite and the pedestrian device and/or vehicle device; (d) repeating (a) to (c) for successive signals so as to obtain successive values of the pseudo-range between each satellite and the pedestrian device and/or vehicle device; (e) computing fluctuations between the successive values of the pseudo-range for each satellite; and (f) while an amplitude of the fluctuations or a function thereof for a given satellite exceeds a preset threshold, ignoring the signals from said satellite.

10. The method according to claim 9, wherein ignoring the fluctuating signals is achieved by setting a signal SNR of said signals to a preset value below a threshold in which the signals are ignored by GPS positioning software in the pedestrian and vehicle devices.

11. A non-transitory computer readable medium storing computer program instructions which when executed by a vehicle navigation device cause the device to carry out the method according to claim 4.

12. A non-transitory computer readable medium storing computer program instructions which when executed by a pedestrian positioning device cause the device to carry out the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0037] FIG. 1 is a pictorial representation of a system according to the invention;

[0038] FIG. 2 is a combined flow chart showing the principal operations carried out by applications in enhanced vehicle and pedestrian location systems according to a first embodiment of the invention;

[0039] FIG. 3 is a combined flow chart showing the principal operations carried out by applications in enhanced vehicle and pedestrian location systems according to a second embodiment of the invention; and

[0040] FIG. 4 is a pictorial representation showing common sources of errors in GPS location systems.

DETAILED DESCRIPTION OF EMBODIMENTS

[0041] FIG. 1 is a pictorial representation of a system 10 according to one embodiment of the invention. The system 10 shows a pedestrian 11 located in a region of interest holding a smartphone 12 having a built-in GPS module that receives GPS signals from at least four satellites 13, 13′ 13″ and 13″′. The GPS signals include the time on which the signals were transmitted by the satellite. The receiver records the time on which the signals were received, and the difference between the times of transmission and receipt reflects the time of flight between the satellites to the receiver, which when multiplied by the speed of light, results in the pseudo-range between the satellites and the receiver. This is referred to as “pseudo-range” because unlike the highly accurate atomic clocks of the satellites, the receiver's clocks are not as accurate. Therefore, at least four satellites are needed to solve for the receiver's coarse location in known manner. Throughout this description and the appended claims, we will refer to this coarse location as the GPS coordinates of the GPS device. Vehicles 14, 14′ that randomly drive through the region of interest likewise receive GPS data from satellites and determine respective coarse locations of the vehicles. For the sake of clarity, each of the vehicles is shown connected to only a single satellite, although in practice each receives signals from at least four satellites, which may or may not be the same as those of other vehicles and may be the same as or different to those from which the smartphone 12 receives its GPS signals. Likewise, although FIG. 1 depicts communication between the smartphone 12 and one or more vehicles, in fact the communication is established between the smartphone 12 and a suitable communications device in each vehicle that is coupled to or is integral with a vehicle navigation system such as WAZE™, SATNAV™ and the like which enhances accuracies in the GPS coordinates so that the correct or true location of each vehicles is known. For the sake of clarity, by “true” or “correct” it is not intended to imply that the corrected locations are precise in absolute terms, but rather that they are significantly more accurate than the coarse locations explained above. Anyone who has used a navigation system such as WAZE™ is well aware that they are instructed in advance to turn left at the next junction and when they are on top of the junction are instructed “turn left”. It is this level of accuracy that renders navigation systems so reliable and user-friendly.

[0042] For the sake of completeness, FIG. 1 shows a second pedestrian 11′ located in broadcast range of the vehicle 14′ so that communication is established between a smartphone 12′ carried by the second pedestrian 11′ and the vehicle 14′. On the other hand, a third pedestrian II″ carrying a smartphone 12″ is out of communication range with any of the vehicles and so no communication is established between a vehicle device and the smartphone 12″. However, all pedestrian smartphones 12, 12′ and 12″ will receive coarse GPS satellite data, although for simplicity not all of the satellite connections are shown in the figure.

[0043] The navigation systems in the vehicles enhance the accuracy for the coarse locations based solely on the satellite signals, using auxiliary data, based for example, on accurate maps that have been pre-compiled and which allow the location of the vehicle to be corrected using known techniques such as snap to map.

[0044] Likewise, techniques such as RADAR, LIDAR and other enhancements being developed for use by Advanced Driver Assistance Systems (ADAS) may be used to determine enhanced location accuracy.

[0045] Although only two vehicles are shown in the figure, it is to be understood that in practice there are thousands of vehicles driving over time along charted routes such as highways, roads, streets and even off-road paths whose locations have been accurately mapped and are accessible to the vehicle navigation systems either because map data is pre-loaded or because they are able to access the map data on-line, typically over the Internet 15. The invention is predicated on the assumption that at any given time, there will be a sufficient flow of traffic in the vicinity of the pedestrian to ensure that at least one vehicle will pass close by and facilitate the transfer of location correction data from the vehicle navigation system to the pedestrian's location device at sufficiently close time intervals.

[0046] The invention is based on the random ad hoc connection between a vehicle navigation system and a pedestrian location device in close proximity to communicate errors in the raw location data as determined by the vehicle navigation system to the pedestrian location device. Owing to the close proximity of the vehicle to the pedestrian, typically less than 50 meters, it may be assumed that the errors are equally applicable or sufficiently so, to allow the pedestrian location device to apply the same errors to its raw determination of location and thereby establish a much more accurate measure of location.

[0047] The required proximity between the smartphone 12 and those vehicles in communication range therewith is achieved by configuring the smartphone 12 and the vehicle devices to communicate by means of a radio protocol whose range is limited such that two devices in communication with one another must be in close proximity (i.e. a short range radio protocol), or by arranging that the devices communicate by means of a radio protocol that is not limited to short range and configuring the pedestrian device to monitor received signal strength between the devices in order to ensure that the devices are in close proximity to one another. For example, the software application resident on the pedestrian device could be configured to use the positioning error of another device only if signals from that other device are received with signal strength above a predetermined level.

[0048] A suitable short range radio protocol is Bluetooth or Bluetooth Low Energy. Bluetooth has a typical maximum range outdoors of around 100 meters for Class 1 devices and around 10 meters for Class 2 devices; Bluetooth Low Energy has a typical maximum range outdoors of around 50 meters.

[0049] In common with the normal Bluetooth™ protocol, BLE also works in 2.4 GHz ISM band, reserved internationally for industrial, scientific and medical (ISM) purposes other than telecommunications. BLE has 40 channels of which 37 are data channels and with 3 are advertising channels, each channel's bandwidth being 2 MHz data packets transmitted between these channels are positioned in two kinds of events: Advertising and Connection events.

[0050] Bluetooth advertising is permission based advertising, which means that when a mobile device receives a Bluetooth message, it has the choice to either accept or decline the message. This is analogous to a pop-up ad that appears in response to an Internet search. The recipient has the choice to click on the ad or ignore it. However, regardless of how the user responds, the web browser receives and displays the ad and is obviously aware of the ad content. So, too, in BLE advertising, the vehicle device sends an ad which is received by any pedestrian device in broadcast range, typically 15 to 40 meters in class 2 Bluetooth enabled mobile devices. Upon receiving the advertisement from the vehicle device, the pedestrian device merely processes the information to extract the error {ΔX, ΔY}, which it then applies to its own coarse positioning to compute a more accurate location. The advertisement packet has 31 data bytes available for use. This should be sufficient to send the error message, but if not, the pedestrian smartphone can request more information from the advertising device without forming a connection through a Scan Request. The BLE vehicle device receives the Scan Request and responds with a Scan response.

[0051] Respective software programs are installed in vehicle and pedestrian navigation systems.

[0052] Thus, referring to FIG. 2, the vehicle program continuously calculates GPS location error based on instantaneous GPS raw positioning and navigation system corrected positioning, and generates an error message {ΔX, ΔY}, which is broadcast as a BLE advertisement. When the vehicle Bluetooth detects an enquiry from a nearby pedestrian smartphone, the vehicle program sends the error message as a response. The pedestrian software program detects the error message as a response to Bluetooth scanning and applies it to the raw GPS positioning obtained by the pedestrian smartphone, resulting in a corrected positioning.

[0053] A software program resident in the pedestrian smartphone scans for BLE to Advertising. When such Advertising is detected from a device in close proximity, the Advertiser error message is decoded to extract the correction {ΔX, ΔY}, which is applied to correct pedestrian positioning. In many urban situations, several vehicles may broadcast different error messages to the pedestrian device in short succession. In such case, the pedestrian device needs to know which of the received messages is most relevant and to discard the other messages. This is achieved by performing RSSI (Received Signal Strength Indicator) analysis on the broadcast signals to determine which is strongest. It may then be assumed that the strongest signal was broadcast by the closest vehicle, for which the error signal is therefore most pertinent. There may, however, be situations where the broadcast range is limited to such a low value, e.g. 10 meters for Class 2 devices that any received error message is sufficiently reliable, in which case such discrimination is unnecessary.

[0054] Alternatively, as shown in FIG. 3, instead of using BLE, standard Bluetooth communication may be used. In this case, the vehicle BT is actuated to be continuously visible and the pedestrian's BT searches for available BT devices. As is known, visible BT devices that are in range of another visible device transmit a standard message containing basic information that identifies the sending device. This information usually includes 48 bits of the device address (BD_ADDR) and another up to 248 bytes of free text, which usually include the Device's name. The vehicle device application in effect changes the name on-the-fly to include the {ΔX, ΔY} correction, i.e. the application continuously replaces some of the 248 bits of the BT message by the correction data. Once a vehicle Bluetooth device is visible to a pedestrian device, the correction {ΔX, ΔY} is received by the pedestrian device and may be extracted and processed as described above. Here also no pairing is needed.

[0055] Obviously, the application software in both the vehicle and pedestrian devices must encode and decode the correction {ΔX, ΔY} in complementary manner. Thus, assuming that the correction {ΔX, ΔY} is appended to the name of the vehicle device, delimiters can be used to separate the value ΔX from the name and to separate between ΔX and ΔY. Alternatively, a fixed number of bytes can be allocated for the name and for each of the component errors ΔX, ΔY.

[0056] The manner in which the device name is changed to include this information is known per se and will typically depend on the operating system of the vehicle device. For example, reference may be made to https://stackoverflow.com/questions/8377558/change-the-android-bluetooth-device-name, which describes how the local Bluetooth name used to identify the device in discovery mode may be changed programmatically using setName(String name) of BluetoothAdapter type, e.g.

TABLE-US-00001 private BluetoothAdapter bluetoothAdapter = null;  bluetoothAdapter = BluetoothAdapter.getDefaultAdapter( );  void ChangeDeviceName( ){   Log.i(LOG, ″localdevicename : ″+bluetoothAdapter.getName( )+″ localdeviceAddress : ″+bluetoothAdapter.getAddress( ));   bluetoothAdapter.setName(″NewDeviceName″);   Log.i(LOG, ″localdevicename : ″+bluetoothAdapter.getName( )+″ localdeviceAddress : ″+bluetoothAdapter.getAddress( )); }

[0057] FIG. 4 shows possible impacts of buildings and other objects on the accuracy of pseudo-range measurement and GPS positioning accuracy. An ideal situation is shown for GPS #1, where there is only direct Line of Sight between the satellite and the receiver. In this case, subject only to atmospheric influence, the measurement of the pseudo-range between the satellite and the receiver is reliable, and provided that all other pseudo-ranges will be as reliable as this one, so too will be the resulting calculated location.

[0058] In the case of GPS #2, there is no direct Line of Sight between the satellite and the receiver, and only a reflected signal is received. In this case, an overestimated, though stable, pseudo-range will be measured, which may result in an error in the final calculated location.

[0059] In the case of GPS #3, both direct and reflected signals are received. These two signals may add to each other with any random phase difference between 0° and 180°, and therefore the resulting pseudo-range may be either overestimated or underestimated. Also, small changes in either the direct signal or the reflected signal may change the relative phase in which they are added, and therefore, unlike in the previous cases, even small changes may cause large differences in the pseudo-range readings. As a result, the resulting pseudo-range will be unstable, subject to random and rapid fluctuations.

[0060] In the embodiments described above, information is shared between the mobile terminal and the on-vehicle device by wireless communication in conformance with the Bluetooth or BLE standards. The use of BT and BLE has been described because of their ubiquity but it will be appreciated that other short-range wireless protocols may be employed such as, WiFi or possibly ZigBee.

[0061] In accordance with another aspect of this invention, there is provided a novel way for filtering out GPS signals resulting from interference between direct and reflected signals, as in the case of GPS #3 in FIG. 4. In this case, unlike GPS #1 and GPS #2, the interference between direct and reflected signals creates unexpected, fluctuating pseudo-range values. Therefore, there is a need to filter out such signals, both in vehicle and pedestrian applications. This may be done by analyzing over time the pseudo-ranges of all satellites and filtering out those which fluctuate over time. This analysis proceeds continuously for all satellites so that the signal of a filtered-out satellite is reinstated as soon as its signal stops fluctuating. “Filtering-out” may be achieved, for example, by setting the signal-to-noise ratio (SNR) of fluctuating satellite signals to zero, causing the location processing to ignore them.

[0062] In this connection it will be borne in mind that GPS satellite signals include SNR as part of the raw data: so this information is already available to both the pedestrian and vehicle GPS systems and indeed is used by GPS positioning systems to ignore satellite signals whose SNR is zero or below some other nominal preset threshold. It is therefore possible to program the software in both devices to set the SNR of an incoming satellite signal to a predetermined SNR threshold below which the signal is ignored while continuing to monitor all incoming signals so that when signal fluctuations from a previously “ignored” satellite exceed the preset SNR threshold, the signal from this satellite is no longer ignored and is used, provided of course that it exceeds the preset threshold.

[0063] For the sake of completeness, it will be appreciated that measurement of fluctuations may be based on a measured amplitude or intensity of the fluctuations such as standard deviation or any suitable function thereof.

[0064] Such a method can be implemented by both the vehicle navigation device and the pedestrian device either in conjunction with the above-described method for improving accuracy of a raw GPS positioning of an untargeted pedestrian device or independently of such a method.

[0065] It will also be understood that the system according to the invention may be a suitably programmed computer. Likewise, the invention contemplates a computer program being readable by a processing unit for executing the method of the invention. The invention further contemplates a non-transitory machine-readable memory tangibly embodying a program of instructions executable by the processing unit for executing the method of the invention.