Proximity-based navigation method

Abstract

A method of improving the raw GPS positioning accuracy of a non-target pedestrian device, wherein the pedestrian device receives a message from a nearby vehicle device, the message containing a calculated offset between the raw GPS position of the vehicle and the corrected position of the vehicle, the receipt of the message being a direct result of the pedestrian device and the vehicle device entering the mutual communication range of a short-range wireless protocol without the 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 position of the pedestrian device.

Description

Technical Field

[0001] This invention relates to navigation systems and methods, and particularly to navigation systems and methods for use by pedestrians. Background Technology

[0002] With the increasing prevalence of smartphones, GPS has become a widely used primary navigation method for pedestrians and drivers. Importantly, pedestrians in urban areas use smartphone GPS as a navigation aid, replacing traditional paper maps. However, due to the low positioning accuracy of GPS systems in mobile phones (primarily in urban areas), using GPS is inconvenient, difficult, and sometimes even impossible for pedestrians. The main reason for the low accuracy of GPS systems in urban areas is that tall buildings obstruct the view of satellites. Furthermore, in some cases, satellite signals reflected from tall buildings are misinterpreted by pedestrian GPS receivers, leading to significant errors in positioning readings. This phenomenon is known as "multipath reflection." Therefore, the positional error depends on the position and time relative to the satellite constellation.

[0003] While multipath reflections affect both motor vehicles and pedestrians, the impact is less pronounced in motor vehicles because they are constantly moving at much higher speeds than pedestrians, and their respective satellite visibility changes rapidly, allowing the error to be smoothed out. Furthermore, since the positions of cars and other road vehicles are confined to the road, techniques such as "map-based navigation" and utilizing IMU data and other information are employed.

[0004] Similarly, cameras, radar, lidar, and other enhanced sensors being developed for advanced driver assistance systems (ADAS) are also being used to improve vehicle positioning accuracy.

[0005] Furthermore, for the development of autonomous vehicles, the positioning accuracy of the secondary lane is crucial, which has led to continuous efforts to improve vehicle positioning accuracy.

[0006] Although the accuracy of vehicle positioning is constantly improving, the positioning error of pedestrians may still be large, which limits the practicality of pedestrian navigation systems.

[0007] This shortcoming has become a major issue for companies like Uber and Lyft, where drivers' ability to successfully pick up passengers relies heavily on the accuracy of the passenger's GPS-reported location. Drivers and customers can miss each other because the customer is across the street or at an intersection. This limitation will become even more critical in the future with the deployment of autonomous taxis.

[0008] Several attempts have been made to improve GPS positioning accuracy, including 3D modeling of surrounding buildings to ignore satellites with multiple reflections, phase analysis, and statistical methods.

[0009] A large body of existing technology relates to the localization of autonomous vehicles and the optimization of localization strategies used by autonomous vehicles based on driving environments (e.g., the geographic area the autonomous vehicle is driving in, the time of day, the vehicle's speed, etc.). In conventional systems, map databases can be used to interpolate locations calculated from navigation satellite system data with physical geographic objects (such as roads) to create a final, more accurate output for display by navigation devices. For example, US20110257885 discloses a method in which the coarse location provided by GPS satellites can be significantly improved, thus providing a location sufficient to guide vehicles, whether autonomous or driven.

[0010] Also known in the art is the use of short-range communication between vehicles and pedestrians, through which vehicles can determine pedestrian location data.

[0011] For example, US20180208140 discloses a vehicle-mounted device that wirelessly communicates with a mobile terminal of a target person located near a vehicle. Positioning signals transmitted by positioning satellites are received by both the mobile terminal and the vehicle-mounted device. The vehicle-mounted device also receives its acquired location from the mobile terminal. By using a correction signal received by the vehicle-mounted device and the acquired location of the target person, the vehicle-mounted device can thus calculate the absolute positions of the vehicle and the mobile terminal with high accuracy based on the corrected positioning signal. The vehicle-mounted device can transmit the vehicle position information along with the corrected terminal position information to the mobile terminal, enabling the mobile terminal to detect the relative position of the vehicle. The vehicle-mounted device can return the vehicle position information and the corrected terminal position information to the mobile terminal. Alternatively, the vehicle-mounted device can return to the mobile terminal the relative distance between the vehicle and the terminal owner calculated based on the vehicle position information and the terminal position information.

[0012] The key advantage of this method is that it allows the onboard device to precisely correct a pedestrian's position even after the pedestrian has transmitted their approximate location to the device. This is useful for taxi drivers or autonomous vehicles to accurately pinpoint the location of waiting passengers. It is indeed possible to transmit the corrected pedestrian position back to the pedestrian, but this must be done proactively by both the vehicle and the pedestrian. In other words, the precise determination of a pedestrian's position is always made by a specific vehicle (usually a taxi) for a specific pedestrian, whose approximate location obtained via the pedestrian's GPS has already been shared with the onboard device.

[0013] This method will allow the target pedestrian to determine his or her precise location. However, it will not allow non-target pedestrians who have not shared their approximate location to make a similar determination.

[0014] U.S. Patent No. 9,213,081 also discloses a system in which two portable devices located close to each other share their respective location data using the Bluetooth Low Energy protocol. The first device includes a Wi-Fi receiver and measures a set of Wi-Fi access points detectable by that device. Typically, the Wi-Fi measurements performed by the device include the BSSID and RSSI (Received Signal Strength Indication) for each access point. The measured data can be shared with a second device, which also has a Wi-Fi receiver but lacks access to the dataset identifying the locations of access points within its local area, and therefore cannot determine its location on its own. Similar techniques can allow two devices to improve their location estimates, or allow two devices to determine their locations when neither set of location data can be used alone. Sharing location data enables devices to detect and / or correct erroneous location estimates.

[0015] In this system, devices communicate autonomously when they enter the communication range, typically within 50 meters according to the Bluetooth Low Energy protocol. However, when transmitting location data from an accessible device to an obstructed device that is not communicating with a set of Wi-Fi access points and therefore cannot accurately determine its location, the obstructed device can at most estimate its location based on the data received by the accessible device. Since the devices can be spaced at most 50 meters apart, the error can be considered small, but the location of the obstructed device is still inaccurate. Furthermore, when both devices are unobstructed, they can both estimate more accurate measurements by sharing their respective location data; by sharing data, they can therefore obtain data from more Wi-Fi access points.

[0016] The document also references https: / / www.bluetooth.com / blog / bluetooth-positioning-systems / , which describes the use of Bluetooth technology to determine the physical location of devices. Traditionally, these systems rely on using received signal strength index (RSSI) measurements to estimate the distance between Bluetooth devices that are part of the system. Using this technique, positioning systems can achieve meter-level accuracy in determining the location of a specific device. This can be further enhanced by adding a direction lookup feature, which allows the system to use both signal strength and direction when determining the location of a device, resulting in even higher accuracy—down to the centimeter level. This technique is used in real-time positioning systems and indoor positioning systems, where the location of a roaming device can be established relative to a fixed device, the location of which is known, and the roaming device can communicate with it via Bluetooth to establish its own location.

[0017] However, these improvements do not help in determining the location of roaming devices, such as by not using fixed Bluetooth.TM (Trademark) Energy Tower's pedestrian navigation system within its broadcast range.

[0018] DE102011051100 discloses a method for improving the accuracy of a pedestrian-held mobile device. A passing vehicle transmits a correction signal to the pedestrian device, which is the difference between the vehicle's coarse GPS position and the corrected position, which can be determined by the vehicle's navigation system or using a fixed reference point whose exact location is known. Using fixed landmarks with known locations to improve the coarse positioning determined by GPS is well-known and is commonly referred to as D-GPS (Differential GPS). D-GPS is also described in US2008 / 0052000. US2013 / 0116908 discloses the use of D-GPS to improve the relative position of a mobile vehicle and a mobile base station. US2009 / 0115656 discloses a system and method for global differential positioning.

[0019] U.S. Patent No. 6,429,808 discloses an integrity monitor for cellular network positioning systems that notifies mobile stations, their users, or the network of measurement quality and warns them of faulty and malfunctioning GPS satellites by isolating the effects of these failures. Whenever a faulty satellite is detected, its corresponding assistance data is excluded from transmission or location determination.

[0020] U.S. Patent No. 5,969,672 discloses a system that determines GPS satellite signal faults by comparing acceleration signals, using an inertial reference and the acceleration signal from a GPS receiver, and monitoring newly acquired GPS satellite signals to determine if satellite drift existed before acquisition. If an unreliable satellite signal is encountered and detected, and at least six satellites are within line of sight and have good geometry, a deselection signal is generated. In this case, a group of five satellite signals can be compared to determine which one (if any) is problematic. If one is identified, this information is passed to a satellite selection function, which eliminates the problematic satellite.

[0021] KR101092914 discloses a method for correcting pseudo-range by eliminating signals from anomalous GPS satellites.

[0022] KR102134862 discloses a method and apparatus for quickly determining a user's location by estimating a coarse location using a distance change rate. Summary of the Invention

[0023] Therefore, one object of the present invention is to improve the positioning accuracy of non-target roaming devices.

[0024] A particular object of the present invention is to provide a method that addresses the need for enhanced pedestrian positioning accuracy by leveraging the increased positioning accuracy of motor vehicles, thereby making pedestrian navigation systems more useful.

[0025] Another objective of this invention is to improve the efficiency of driver-passenger encounters.

[0026] Another objective of this invention is to filter out fluctuating satellite signals transmitted from satellites to the GPS positioning device in the GPS positioning system.

[0027] According to different aspects of the invention, these objectives are achieved by methods according to the respective independent claims.

[0028] Specifically, according to one aspect of the present invention, a method for improving the original GPS positioning accuracy of a non-target pedestrian device is provided, the method comprising:

[0029] a. The pedestrian device is connected via Bluetooth. TM Nearby vehicle devices within the communication range receive a message containing a calculated offset between the vehicle's original GPS location and the vehicle's corrected location. The message is a pop-up notification that encapsulates the calculated offset and can be received without pairing between the two devices.

[0030] b. The pedestrian device ensures that the vehicle is within a sufficiently narrow range of the pedestrian device, in order to use Bluetooth, which only allows communication between the two vehicles within that narrow range. TM The protocol makes the received offset applicable to the pedestrian device;

[0031] c. The pedestrian device decodes the message to extract the calculated offset; and

[0032] d. Apply the calculated offset to the original GPS positioning of the pedestrian device to obtain a more accurate location of the pedestrian device.

[0033] According to another related aspect of the present invention, a method for improving the accuracy of raw GPS positioning of a non-target pedestrian device is provided, the method comprising:

[0034] a. The pedestrian device receives a message containing a calculated offset between the vehicle's original GPS location and the vehicle's corrected location from a nearby vehicle device within the short-range wireless protocol communication range. The message is a pop-up notification that encapsulates the calculated offset and can be received without pairing between the two devices.

[0035] b. The pedestrian device ensures that the vehicle is within a sufficiently narrow range of the pedestrian device so that the received offset is applied to the pedestrian device by associating only signals from passing vehicles whose measured signal strength exceeds a predetermined threshold.

[0036] c. The pedestrian device decodes the message to extract the calculated offset; and

[0037] d. Apply the calculated offset to the original GPS positioning of the pedestrian device to obtain a more accurate location of the pedestrian device.

[0038] Most mobile communication devices (such as smartphones) are equipped with short-range wireless communication (such as Bluetooth). TM Bluetooth Low Energy (BLE) is designed for short-range communication with other devices. When a first such device is brought into a second device equipped with Bluetooth... TM When a BLE-like device is within broadcast range, the first device will be detected by the second device, and they will exchange a message containing a 48-bit unique device ID (Mac-Add). If it's Bluetooth... TM There is also an additional 48 bytes of free-format device description (such as "Samsung S8").

[0039] This invention utilizes this communication to transfer GPS positioning errors {ΔX, ΔY}, derived from the vehicle's original GPS positioning and corrected positioning, from nearby motor vehicles to non-target pedestrians located near the vehicle. The corrected data {ΔX, ΔY} can be transmitted as a response to a pedestrian telephone scan, described using a free-format device. How the error is estimated by the navigation system is not a specific feature of this invention and is known in itself. For our purposes, it is sufficient to understand that the vehicle navigation system receives raw GPS data corresponding to a coarse location in space, which can be represented by coordinates {x, y, z} relative to a predetermined origin (e.g., the center of mass of the entire Earth system). These coordinates correspond to latitude, longitude, and altitude. In practice, altitude can be ignored because it can be assumed that any altitude difference is negligible when the pedestrian and vehicle are within short-range communication range. Therefore, the difference between the received latitude and longitude coordinates and the corresponding accurate coordinates constitutes the error {ΔX, ΔY}.

[0040] In this way, a pedestrian standing near the road initiates a Bluetooth scan, so any vehicle passing by will be queryed and will transmit back a GPS position error via the application according to the invention. This error is determined by the vehicle's original GPS location and its corrected location. Once received by the pedestrian device, the {ΔX, ΔY} correction can be applied to the pedestrian's GPS location via the application according to the invention. This can be accomplished via standard Bluetooth communication or BLE (Bluetooth Low Energy) communication. In both cases, as explained below, pairing is not required between the pedestrian BT device and the vehicle BT device.

[0041] In the context of the description and appended claims, the term "non-target" is used to refer to a pedestrian device that is not specifically processed by the vehicle device. Instead, depending on the wireless protocol employed, the vehicle device transmits its estimated error, which is received by the pedestrian device within communication range. Before reception, the pedestrian device is unknown to the vehicle device, and vice versa. After reception, the vehicle's identity is known to the pedestrian device, and vice versa, but in both cases, pairing is not initiated between the two devices.

[0042] In one embodiment, standard Bluetooth communication is used. In this case, the vehicle's Bluetooth device (BT) is set to be visible at all times, and the pedestrian's BT device searches for available BT transmitters. The software application in the vehicle device encodes the correction {ΔX, ΔY} as part of the vehicle device name. Bluetooth standard information typically includes a 48-bit vehicle device address (BD_ADDR) and up to 248 additional bytes, which typically include the vehicle device name. These bytes are modified by the vehicle device application to include the {ΔX, ΔY} correction; that is, the application continuously replaces some of the 248 bits of the BT message with the correction data. Once a pedestrian detects the vehicle's Bluetooth device, the software application in the pedestrian device extracts the correction {ΔX, ΔY} from the received vehicle device name. Importantly, pairing is not required because the Bluetooth protocol allows the pedestrian device to recognize the name of any Bluetooth device within range without exchanging data. Instead, the pedestrian device's name is known to the vehicle device, but its location is unknown.

[0043] In a similar manner, Bluetooth Low Energy (BLE) can be used. The vehicle, acting as an advertiser, periodically transmits {ΔX, ΔY} positioning corrections related to its current location. When a pedestrian scans, they receive the {ΔX, ΔY} corrections in response.

[0044] To ensure that the vehicle is indeed near the pedestrian, in both cases, the received signal strength (Received Signal Strength Indication, RSSI) can be used by the pedestrian's receiver as an indication of the distance between the vehicle and the pedestrian. In this way, {ΔX, ΔY} corresponding to the maximum RSSI and thus the minimum distance will be used. Attached Figure Description

[0045] To understand the invention and how it can be practiced, embodiments will now be described by way of non-limiting means with reference to the accompanying drawings, in which:

[0046] Figure 1 This is a graphical representation of the system according to the present invention;

[0047] Figure 2 This is a combined flowchart illustrating the main operations performed in the application of the enhanced vehicle and pedestrian positioning system according to a first embodiment of the present invention;

[0048] Figure 3 This is a combined flowchart illustrating the main operations performed in the application of the enhanced vehicle and pedestrian positioning system according to a second embodiment of the present invention; and

[0049] Figure 4 This is a graphical representation illustrating common sources of error in GPS positioning systems (prior art). Detailed Implementation

[0050] Figure 1 This is a schematic representation of system 10 according to an embodiment of the present invention. System 10 shows a pedestrian 11 located in the area of ​​interest of a handheld smartphone 12, which has 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 the satellites transmitted the signals. A receiver records the time the signal was received, and the difference between the transmission and reception times reflects the flight time between the satellite and the receiver. When this flight time is multiplied by the speed of light, a pseudo-range between the satellite and the receiver is obtained. This is called a "pseudo-range" because the receiver's clock is not as precise as the highly accurate atomic clocks of the satellites. Therefore, at least four satellites are required to resolve the rough position of the receiver in a known manner. In this description and the appended claims, we will refer to this rough position as the GPS coordinates of the GPS device. Vehicles 14, 14′ randomly passing through the area of ​​interest also receive GPS data from the satellites and determine their respective rough positions. For clarity, each vehicle is shown as connected to only one satellite, but in reality, each vehicle receives signals from at least four satellites, which may be the same or different from the satellites used by other vehicles, and may be the same or different from the satellites used by the smartphone 12 to receive GPS signals. Similarly, although... Figure 1 The text describes communication between a smartphone 12 and one or more vehicles, but in reality, this communication is established between the smartphone 12 and a suitable communication device in each vehicle, which in turn communicates with the vehicle's navigation system (such as WAZE). TM SATNAV TMBy integrating GPS coordinates (such as WAZE, etc.), this vehicle navigation system improves the accuracy of GPS coordinates, thus allowing the correct or true location of each vehicle to be determined. For clarity, "true" or "correct" does not mean that the corrected location is absolutely precise, but rather that it is much more accurate than the approximate location explained above. Anyone who has used WAZE... TM People familiar with navigation systems know that they are instructed beforehand to turn left at the next intersection, and when they are at the intersection, they are instructed to "turn left." It is this level of precision that makes navigation systems so reliable and user-friendly.

[0051] For the sake of completeness, Figure 1 A second pedestrian 11' is shown within the broadcast range of vehicle 14', allowing communication to be established between the smartphone 12' carried by the second pedestrian 11' and vehicle 14'. On the other hand, a third pedestrian 11' carrying smartphone 12' is not within the communication range of any vehicle, thus no communication is established between the vehicle and smartphone 12'. However, all pedestrians' smartphones 12, 12', and 12' will receive coarse GPS satellite data, but for simplicity, not all satellite connections are shown in the figure.

[0052] The navigation system in the vehicle is based solely on satellite signals and uses auxiliary data, such as a precise map that has been pre-compiled and allows the use of known techniques (such as map-based navigation) to correct the vehicle's position, to improve the accuracy of the rough location.

[0053] Similarly, technologies such as radar, lidar, and other enhancement processing technologies being developed for advanced driver assistance systems (ADAS) can be used to determine enhanced positioning accuracy.

[0054] Although only two vehicles are shown in the diagram, it should be understood that in practice, thousands of vehicles travel over time along mapped routes such as highways, roads, streets, and even off-road trails. The locations of these routes are precisely mapped and accessible to vehicle navigation systems, either because the map data is pre-loaded or because it is accessible online (typically via the Internet). The premise of this invention is that at any given time, there will be sufficient traffic flow near the pedestrian to ensure that at least one vehicle passes by in the vicinity, facilitating the transmission of position correction data from the vehicle navigation system to the pedestrian positioning device within sufficiently short time intervals.

[0055] This invention is based on a random, temporary connection between a vehicle navigation system and a very close pedestrian positioning device, in order to transmit errors in the raw location data determined by the vehicle navigation system to the pedestrian positioning device. Since the distance between the vehicle and the pedestrian is very close (typically less than 50 meters), it can be assumed that these errors are equally or sufficiently applicable, allowing the pedestrian positioning device to apply the same errors to its raw location determination, thereby establishing a more accurate location measurement.

[0056] The required proximity between the smartphone 12 and the vehicles within its communication range is achieved by configuring the smartphone 12 and the vehicle devices to communicate via a radio protocol whose range is limited to two devices that must be close to each other (i.e., a short-range radio protocol), or by arranging these devices to communicate via a radio protocol not limited to short range and configuring pedestrian devices to monitor the received signal strength between the devices to ensure that the devices are close to each other. For example, a software application residing on a pedestrian device can be configured to use the device's positioning error only when a signal is received from another device and the signal strength is above a predetermined level.

[0057] Suitable short-range radio protocols are Bluetooth or Bluetooth Low Energy. For Class 1 devices, the typical maximum outdoor range of Bluetooth is around 100 meters, and for Class 2 devices, it is around 10 meters. Bluetooth Low Energy's typical maximum outdoor range is around 50 meters.

[0058] With regular Bluetooth TM Like the protocol, BLE also operates in the 2.4 GHz ISM band, which is internationally reserved for industrial, scientific, and medical (ISM) purposes other than telecommunications. BLE has 40 channels, 37 of which are data channels and 3 are advertising channels, each with a bandwidth of 2 MHz. Data packets transmitted between these channels are positioned in two events: advertising and connection events.

[0059] Bluetooth advertising is permission-based advertising, meaning that when a mobile device receives a Bluetooth message, it can choose to accept or reject it. This is similar to pop-up ads that appear in internet searches. The recipient can choose to click on the ad or ignore it. However, regardless of the user's response, the web browser receives and displays the ad and is obviously aware of its content. Therefore, in BLE advertising, the ad sent by the vehicle device is received by any pedestrian device within its broadcast range (typically 15 to 40 meters for Bluetooth-enabled Class 2 mobile devices). Upon receiving the ad from the vehicle device, the pedestrian device simply processes the information to extract the error {ΔX, ΔY} and then applies it to its own coarse positioning to estimate a more accurate location. The ad packet has 31 data bytes available. This should be sufficient to send the error message, but if not, the pedestrian's smartphone can request more information from the advertising device via a scan request without having to form a connection. The BLE vehicle device receives the scan request and responds with a scan response.

[0060] The corresponding software programs are installed in vehicle and pedestrian navigation systems.

[0061] Therefore, refer to Figure 2 The vehicle's software continuously calculates GPS position errors based on instantaneous raw GPS positioning and navigation system-corrected positioning, generating error messages {ΔX, ΔY}, which are then broadcast as BLE advertisements. When the vehicle's Bluetooth detects an inquiry from a nearby pedestrian's smartphone, the vehicle's software sends the error messages as a response. The pedestrian software detects the error messages as a response to the Bluetooth scan and applies them to the raw GPS positioning obtained from the pedestrian's smartphone, thereby generating a corrected positioning.

[0062] Software residing in pedestrian smartphones scans for BLE advertisements. When such an advertisement is detected from a nearby device, the advertiser's error message is decoded to extract a correction {ΔX, ΔY}, which is then applied to correct the pedestrian's location. In many urban situations, several vehicles may broadcast different error messages to pedestrian devices consecutively within a short period. In this case, the pedestrian device needs to know which received message is most relevant and discard the others. This can be achieved by performing RSSI (Received Signal Strength Indication) analysis on the broadcast signal to determine which signal is strongest. It can then be assumed that the strongest signal was broadcast by the nearest vehicle, and therefore the error signal is most relevant to it. However, there may be situations where the broadcast range is limited to such a low value (e.g., 10 meters for a Class 2 device) that any received error message is sufficiently reliable, in which case such differentiation is unnecessary.

[0063] Alternative locations, such as Figure 3As shown, BLE can be omitted, and standard Bluetooth communication can be used instead. In this case, the vehicle's Bluetooth device is activated to be continuously visible, and the pedestrian's Bluetooth device searches for available Bluetooth devices. It is well known that a visible Bluetooth device within range of another visible device transmits a standard message containing basic information identifying the transmitting device. This information typically includes a 48-bit device address (BD_ADDR) and an additional 248 bytes of free text, which usually includes the device's name. The vehicle device application essentially changes the name on the fly to include {ΔX, ΔY} corrections; that is, the application continuously replaces some of the 248 bits of the Bluetooth message with correction data. Once the vehicle's Bluetooth device becomes visible to the pedestrian device, the pedestrian device receives the {ΔX, ΔY} corrections, which can be extracted and processed as described above. Pairing is not required here.

[0064] Clearly, the application software in both vehicle and pedestrian devices must encode and decode the corrections {ΔX, ΔY} in a complementary manner. Therefore, assuming the corrections {ΔX, ΔY} are appended to the name of the vehicle device, delimiters can be used to separate the numerical value ΔX from the name, and to separate ΔX and ΔY. Alternatively, a fixed number of bytes can be allocated to the name and the errors ΔX and ΔY for each component.

[0065] The way device names are changed to include this information is known in itself and typically depends on the vehicle device's operating system. For example, see https: / / stackoverflow.com / questions / 8377558 / change-the-android-bluetooth-device-name, which describes how to programmatically change the local Bluetooth name used to identify devices in discovery mode using the `setName(string name)` method of type `BluetoothAdapter`, for example:

[0066] Figure 4 The diagram illustrates the potential impact of buildings and other objects on the accuracy of pseudorange measurements and GPS positioning. The figure shows the ideal scenario for GPS#1, where there is only a direct line of sight between the satellite and the receiver. In this case, the pseudorange measurement between the satellite and the receiver is reliable, affected only by the atmosphere, and the calculated position will also be reliable provided that all other pseudoranges are as reliable as this one.

[0067] In the case of GPS#2, there is no direct line of sight between the satellite and the receiver; only reflected signals are received. In this situation, an overestimated, but stable, pseudo-range will be measured, which may lead to errors in the final calculated position.

[0068] In the case of GPS#3, both direct and reflected signals are received. These two signals can be added to each other with any random phase difference between 0 and 180 degrees, thus the resulting pseudo-range may be overestimated or underestimated. Furthermore, small changes in either the direct or reflected signal can alter the relative phase of their addition; therefore, unlike the previous case, even small changes can lead to significant differences in pseudo-range readings. Consequently, the resulting pseudo-range will be unstable, subject to random and rapid fluctuations.

[0069] In the above embodiments, the mobile terminal and the vehicle-mounted device share information via wireless communication conforming to Bluetooth or BLE standards. While the use of Bluetooth and BLE has been described due to their prevalence, it is understood that other short-range wireless protocols, such as WiFi or, possibly, ZigBee, can be employed.

[0070] According to another aspect of the invention, a novel method is provided for filtering GPS signals generated by interference between direct and reflected signals, such as... Figure 4 The case of GPS#3 is an example. Unlike GPS#1 and GPS#2, interference between direct and reflected signals in this scenario produces unexpected, fluctuating pseudo-range values. Therefore, in vehicle and pedestrian applications, it is necessary to filter out these signals. This can be achieved by analyzing the pseudo-ranges of all satellites and filtering out those that fluctuate over time. This analysis is performed continuously on all satellites, so once the signals of the filtered satellites stop fluctuating, their signals return to normal. For example, "filtering" can be achieved by setting the signal-to-noise ratio (SNR) of fluctuating satellite signals to zero, causing the positioning process to ignore them.

[0071] In this regard, it's important to remember that GPS satellite signals include signal-to-noise ratio (SNR) as part of the raw data. This information is therefore available to both pedestrian and vehicle GPS systems; in fact, GPS positioning systems use this information to ignore satellite signals with an SNR of zero or below certain other preset thresholds. Thus, it's possible to program the software in both devices to set the SNR of incoming satellite signals to a predetermined threshold, ignoring signals below that threshold, while continuing to monitor all incoming signals so that when a signal fluctuation from a previously "ignored" satellite exceeds the predetermined SNR threshold, the signal from that satellite is no longer ignored and is used, provided, of course, that it exceeds the predetermined threshold.

[0072] For the sake of completeness, it is understood that measurements of fluctuations can be based on the measured amplitude or intensity of the fluctuation, such as the standard deviation or any suitable function thereof.

[0073] Such methods can be implemented by vehicle navigation devices and pedestrian devices, either in conjunction with the methods described above for improving the accuracy of the original GPS positioning of non-target pedestrian devices, or independently of such methods.

[0074] It is also understood that the system according to the invention can be a suitably programmed computer. Similarly, the invention also contemplates computer programs that can be read by a processing unit to execute the methods of the invention. The invention further contemplates machine-readable memory that tangibly embodies a program of instructions executable by a processing unit to perform the methods of the invention.

Claims

1. A method for improving the raw GPS positioning accuracy of a non-target pedestrian device, the method comprising: a. A vehicle device that is close to the non-target pedestrian device, the vehicle device including a vehicle device name field, the vehicle device name field including information identifying the vehicle device and a calculated offset between the original GPS location of the vehicle device and the corrected location of the vehicle; b. The non-target pedestrian device receives a message containing the vehicle device name field from a nearby vehicle within Bluetooth communication range, and the reception of the message does not require pairing between the two devices. c. The non-target pedestrian device ensures that the vehicle device is within a sufficiently narrow range of the non-target pedestrian device so that the calculated offset is applicable to the non-target pedestrian device, wherein the sufficiently narrow range corresponds to a range in which a Bluetooth signal can be detected, wherein the method for detecting the Bluetooth signal is selected from one of the following detection methods: This is achieved by using the Bluetooth protocol, which only allows mutual communication within a sufficiently narrow range; and, By associating only the signals from passing vehicles whose measured signal strength exceeds a predetermined threshold; d. The non-target pedestrian device decodes the message to extract the calculated offset; and, e. Apply the calculated offset to the original GPS positioning of the non-target pedestrian device to obtain a more accurate location of the non-target pedestrian device.

2. The method of claim 1, wherein the vehicle device is configured to: a. Obtain the approximate location of the vehicle device; b. Obtain the calibration position of the vehicle device; c. Calculate the calculated offset; and d. When within the communication range of the vehicle device, the calculated offset is encoded in Bluetooth in the message of the vehicle device for decoding by the non-target pedestrian device.

3. The method of claim 1 or 2, further comprising the following operations performed by the non-target pedestrian device: a. Receive multiple corresponding signals from different vehicles within the communication range of the non-target pedestrian device, each signal containing a corresponding offset. ; b. For each received signal, determine the corresponding signal strength based on RSSI; and, c. Using the corresponding offset from any of the signals having the largest RSSI. .

4. The method of claim 1 or 2, used to allow a vehicle to locate a pedestrian, the method further comprising: a. Receive the corrected position from the non-target pedestrian device; as well as, b. Locate the pedestrian based on the received corrected position.

5. The method of claim 1 or 2, wherein at least one of the non-target pedestrian device and the vehicle device filters out fluctuating satellite signals in the following manner: a. Receive corresponding GPS signals from at least four satellites and identify the transmission time; b. Determine the reception time of the GPS signal; c. Calculate the effective elapsed time and the pseudo-range between the satellite and the non-target pedestrian device and / or the vehicle device; d. Repeat a to c for the continuous signals to obtain continuous values ​​of the pseudo-range between each satellite and the non-target pedestrian device and / or the vehicle device; e. Calculate the fluctuations between the consecutive values ​​of the pseudo-range for each satellite; and, f. When the fluctuation amplitude or function of a given satellite exceeds a preset threshold, the signal from the satellite is ignored.

6. The method of claim 5, wherein the signal fluctuation is ignored by setting the signal-to-noise ratio of the signal to a preset value below a threshold, at which the GPS positioning software in the pedestrian and vehicle devices ignores the signal.

7. A computer-readable medium storing computer program instructions that, when executed by a vehicle navigation device, cause the device to perform the method as described in claim 2.

8. A computer-readable medium storing computer program instructions that, when executed by a pedestrian positioning device, cause the device to perform the method as described in any one of claims 1, 3 to 6.

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