Local positioning system for areas where global navigation satellite systems are rejected

Abstract

The invention relates to a local positioning system for areas where global navigation satellite systems are rejected. A navigation system is provided. A GNSS receiver is used to receive satellite signals from a plurality of satellites, and a local positioning system (LPS) receiver is used to receive LPS signals from a plurality of fixed location LPS transmitters positioned to form an LPS coverage area. A controller is in communication with the GNSS receiver and the LPS receiver. The controller is configured to use the LPS signal to determine a location of the vehicle when the vehicle is within the LPS coverage area and within a coverage area where GNSS is rejected. The LPS coverage area is an area that provides the LPS signals from at least four fixed location LPS transmitters. Each LPS signal from each LPS transmitter includes LPS transmitter position information and clock information used by the controller of the vehicle to determine the position of the vehicle.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Indian Provisional Application No. 202311076588 filed on November 9, 2023, having the same title as the present application, which is incorporated herein by reference in its entirety. Background Art

[0003] Air vehicles (including manned vehicles and autonomous vehicles) generally rely on highly accurate navigation systems when traversing travel paths. In some applications, the vehicle is required to quickly and accurately locate (position initialization) to avoid obstacles in an unknown environment. One type of navigation system for determining the position of an aerial vehicle mixes an inertial navigation system (INS) with a global navigation satellite system (GNSS) such as a global positioning system (GPS). In a GNSS-denied environment (an area where there are no satellite signals from enough satellites required to determine the position), navigation of vehicles (especially air vehicles) may also be a challenge even with a hybrid navigation system.

[0004] Furthermore, as cities and suburbs grow, the number of GNSS-denied areas increases with the addition of tall buildings. Alternative navigation technologies using sensors like cameras, light detection and radar (LiDAR), radar, radio equipment, and star trackers have been used to augment and improve INS data in GNSS-denied areas. However, these existing alternative navigation solutions have accuracy and availability limitations and may not be accurate enough to meet current and future aviation needs.

[0005] For the reasons stated above and other reasons described below, which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a robust and accurate system for providing position information for vehicle navigation in GNSS-denied areas. Summary of the invention

[0006] The following summary is made by way of example and not by way of limitation. The purpose of providing the summary is merely to help the reader understand some aspects of the subject matter. Embodiments use a local positioning system (LPS) to supplement GNSS, such as but not limited to GPS in GNSS-denied areas.

[0007] In one embodiment, a method for determining the position of a vehicle is provided. The method includes: when a global navigation satellite system (GNSS) receiver of the vehicle is receiving satellite signals from at least four satellites of the GNSS, using the GNSS to determine the position of the vehicle; and when the vehicle is within an LPS coverage area of ​​a local positioning system (LPS), using the LPS to determine the position of the vehicle, wherein the LPS coverage area is an area that provides LPS signals from at least four fixed-position LPS signal transmitters, each LPS signal from each LPS transmitter includes transmitter position information and clock information used by a controller of the vehicle to determine the position of the vehicle.

[0008] In another embodiment, a navigation system is provided. The vehicle position determination system includes a GNSS receiver, an LPS positioning system receiver, a memory, and a controller. The GNSS is used to receive satellite signals from a plurality of satellites. The LPS receiver is used to receive LPS signals from a plurality of fixed position LPS transmitters, which are positioned to form an LPS coverage area. The memory is used to store at least operating instructions. The controller communicates with the GNSS receiver, the LPS receiver, and the memory. The controller is configured to use the LPS signal to determine the position of the vehicle when the vehicle is within the LPS coverage area and within the coverage area where the GNSS is denied. The LPS coverage area is an area where the LPS signals from at least four fixed position LPS transmitters are provided. Each LPS signal from each LPS transmitter includes LPS transmitter position information and clock information used by the controller of the vehicle to determine the position of the vehicle.

[0009] In yet another embodiment, another vehicle position determination system using LPS is provided. The vehicle position determination system includes a display, a GNSS receiver, an LPS positioning system receiver, an INS, a memory, and a controller. The GNSS receiver is used to receive satellite signals from a plurality of satellites. The LPS receiver is used to receive LPS signals from a plurality of fixed position LPS transmitters, which are positioned to form an LPS coverage area. The INS is used to determine at least a relative measurement of a given initial reference. The memory is used to store at least operating instructions. The memory includes a database, which includes at least a GNSS coverage area and an LPS coverage area. The controller communicates with the GNSS receiver, the LPS receiver, the INS, the memory, and the display. The controller is configured to use the LPS signal to determine the position of the vehicle when the vehicle is within the LPS coverage area and within the coverage area where the GNSS is denied. The LPS coverage area is an area where the LPS signals from at least four fixed position LPS transmitters are provided. Each LPS signal from each LPS transmitter includes LPS transmitter position information and clock information used by the controller of the vehicle to determine the position of the vehicle. The controller is further configured to calibrate the INS using the position of the vehicle determined using the LPS.The controller is further configured to display the GNSS coverage area and the LPS coverage area stored in the database using the display. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention may be more readily understood and further advantages and uses of the present invention will become more apparent when considered in light of the detailed description and the following drawings, in which:

[0011] Figure 1 is an illustration of an aircraft traveling in a GPS-denied environment according to an example aspect of the present invention;

[0012] Figure 2 is a block diagram of a navigation system according to an example aspect of the present invention;

[0013] Figure 3A A method of determining a position of a vehicle in a vehicle position flow chart according to an example aspect of the present invention is illustrated;

[0014] Figure 3B A method of using an LPS in an LPS flow chart according to an exemplary aspect of the present invention is illustrated;

[0015] Figure 4 illustrates a transmitter information flow diagram according to an example aspect of the present invention;

[0016] Figure 5illustrating an integrity check positioning computation graph according to an example aspect of the invention;

[0017] Figure 6 illustrates a location integrity flow chart according to an example aspect of the present invention;

[0018] Figure 7 A flow chart illustrating vehicle operations according to an example aspect of the present invention;

[0019] Figure 8 illustrates a coverage area flow chart according to an example aspect of the present invention;

[0020] Fig. 9 illustrates an overlapping transition flow chart according to an example aspect of the invention;

[0021] Fig.10 illustrates a coordinated vehicle movement flow chart according to an example aspect of the invention; and

[0022] Fig.11 An error correction flow diagram according to an example aspect of the invention is illustrated.

[0023] As is common practice, the various features described are not necessarily drawn to scale, but rather are used to emphasize specific features relevant to the present invention. Reference characters denote similar elements throughout the drawings and text. DETAILED DESCRIPTION

[0024] In the following specific embodiments, reference is made to the accompanying drawings, which form a part of the specific embodiments, and in these drawings, specific embodiments that can implement the present invention are shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, and it should be understood that other embodiments can be utilized and can be changed without departing from the spirit and scope of the present invention. Therefore, the following specific embodiments are not restrictive, and the scope of the present invention is limited only by the claims and their equivalents.

[0025] Embodiments of the present invention use a navigation system including a local positioning system (LPS) that supplements a global navigation satellite system (GNSS) such as, but not limited to, a global positioning system (GPS). In one example, the LPS includes an LPS positioning controller that can be hosted in a high integrity navigation receiver. The LPS positioning controller is configured to perform LPS calculations on received LPS signals to determine the location of an associated vehicle. The LPS signals are provided by a plurality of transmitters. Each transmitter is integrated with a high resolution atomic clock. The transmitters are installed at strategic locations of available urban infrastructure (street lights, transmission towers, mobile communication towers, buildings, etc.) in GNSS inaccessible areas (GNSS denied areas) in urban aerial areas to create LPS coverage areas.

[0026] refer to Figure 1 , illustrates an example vehicle 100 that uses LPS 201 (eg, Figure 2 1 (shown in FIG. 1 ). In this example, the vehicle 100 is shown as an aircraft; however, any type of vehicle that uses a navigation system (i.e., any type of airborne, land-based, or water-based vehicle, whether manned or unmanned) can implement LPS 201 for navigation. In addition, LPS 201 can be used to supplement other navigation systems of vehicles in areas where GNSS is denied.

[0027] exist Figure 1 In the example of FIG. 1 , satellites 102-1, 102-2, 102-3, through 102-n generate satellite signals used by vehicle 100 for navigation purposes. However, there are areas where satellite signals from multiple different satellites (generally represented by 102) needed to determine position cannot reach. These areas are referred to herein as "GNSS denied areas." Examples of GNSS denied areas are Figure 1 1. A GNSS denied area 130 is a GNSS denied area 130 in a vehicle such as vehicle 100. In this GNSS denied area 130, a vehicle such as vehicle 100 may try and rely on other navigation systems, such as but not limited to an inertial navigation system (INS). GNSS denied areas may occur due to objects, such as buildings and terrain, that block satellite signals from reaching the GNSS denied area. There may also be overlapping coverage areas, such as overlapping coverage area 132, where both GNSS and LPS may be used to determine vehicle position (location) information. In one example, when both GNSS and LPS are available, GNSS position is used.

[0028] Embodiments provide for the possibility of using the LPS in areas such as Figure 1LPS 201 is used within LPS coverage area 120 of vehicle 100. LPS 201 includes LPS transceivers 104-1, 104-2, 104-3, 104-n, which are positioned to radiate LPS signals within LPS coverage area 120. LPS 201 also includes LPS receiver 204 in vehicle 100 (in Figure 2 ), the LPS receiver is configured to receive and process the LPS signal to determine navigation information (such as positioning or location information), as discussed below. As discussed above, the LPS transceiver (generally represented by 104) can be located on street lights, transmission towers, mobile communication towers, sidewalks, buildings, etc. to cover Figure 1 The LPS coverage area 120 is illustrated in FIG.

[0029] Figure 2 A block diagram of a vehicle 100 is illustrated in FIG. Figure 2 A navigation system 200 of a vehicle 100 and navigation components of an LPS 201 are illustrated. In this example, the navigation system 200 of the vehicle 100 includes a controller 202 and a memory 210.

[0030] Generally, the controller 202 may include any one or more of a processor, a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or an equivalent discrete or integrated logic circuit. In some example embodiments, the controller 202 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, one or more FPGAs, and other discrete or integrated logic circuits. The functions attributed to the controller 202 herein may be embodied as software, firmware, hardware, or any combination thereof. The controller 202 may be part of a system controller or a component controller (such as a component controller of the LPS receiver 204). The memory 210 may include computer readable operating instructions that provide positioning functions when executed by the controller 202. Such positioning functions may include implementing the functions of the LPS described below. The computer readable instructions may be encoded in the memory 210. Memory 210 is a suitable non-transitory storage medium, including any volatile, nonvolatile, magnetic, optical, or electrical medium, such as, but not limited to, random access memory (RAM), read-only memory (ROM), nonvolatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, or any other storage medium.

[0031] The navigation system 200 of the vehicle 100 also includes a GNSS receiver 208 and an associated GNSS antenna 203, an inertial navigation system (INS) 206, and an LPS receiver 204 with an associated LPS antenna 209. The GNSS receiver 208 is designed to receive satellite signals from the satellites 102-1 to 102-n through the GNSS antenna 203 and determine range information to each associated satellite 102-1 to 102-n. When satellite signals from a sufficient number of satellites (at least four) are received at the GNSS receiver 208, the range information is used to determine the position information of the vehicle 100. The controller 202 communicates with the GNSS receiver 208.

[0032] The INS 206 is also in communication with the memory 202. The INS 206 provides relative measurements given an initial reference. The controller 202 can use the relative measurements to determine the position, orientation, and speed of the vehicle 100. However, these relative measurements can accumulate drift errors over time.

[0033] As discussed above, the LPS 201 includes an LPS receiver 204 and an associated LPS antenna 209 and LPS transmitters 104-1 to 104-n located at specific locations to create an LPS coverage area 120. Each transmitter 104-1 to 104-n includes an associated antenna 105-1, 105-2, 105-3 to 105-n. In one example, the LPS transmitters 104-1 to 104-n transmit signals using radio frequency (RF). Further in one example, each LPS transmitter 104-1 to 104-n uses its own unique frequency. In this example, the controller 202 can identify the LPS transmitters 104-1 to 104-n by looking up the associated LPS transmitters in the database 212 in the memory 210. Through the associated database information, the location of each LPS transmitter 104-1 to 104-n can be found. In another embodiment, each LPS transmitter 104-1 through 104-n includes LPS transmitter location information in its transmissions.

[0034] As discussed above, the memory 210 may include a database 212 having LPS coverage information including the locations of the LPS transmitters 104-1 through 104-n. In one example, the database 212 may include Figure 1 In one example, the GNSS coverage area 118, the LPS coverage area 120, and the GNSS denied area 130 are displayed on the display 218 for the crew member.

[0035] In one embodiment, the controller 202 is configured to add LPS coverage area information that is not already in the database 212 when detected, and can then communicate the information to a remote location via the communication system 214. The remote location can compile the LPS coverage area information for the database 212 and distribute the information to other vehicles. The controller 202 can also use the communication system 214 to communicate the determined location information of the vehicle 100.

[0036] The vehicle is also shown to include a vehicle control system 216 for at least partially controlling the operation of the vehicle 100, including the direction of travel in one example. In addition, in one example, the controller 202 controls the operation of the vehicle 100 through the vehicle control system 216 based at least in part on the determined position information.

[0037] In one example, the controller 202 uses position information derived from signals from LPS transmitters 104-1 to 104-n when satellite signals from satellites 102-1 to 102-n are not available (i.e., when in an LPS coverage area) or when satellite signals are inaccurate for navigation. In other embodiments, the controller 202 supplements the position information determined by one of satellite signals and inertial signals from the INS 206 with position information determined by received LPS signals from transmitters 104-1 to 104-n. In yet another embodiment, signals from transmitters 104-1 to 104-n are used to determine position information for the vehicle 100. As discussed above, the LPS described herein may be applied to any type of mobile vehicle, including but not limited to any type of aircraft (including drones) and any land-based or water-based vehicle.

[0038] Figure 3A The general method of determining the location of a vehicle is illustrated in the vehicle location flowchart 301 of FIG. The vehicle location flowchart 301 is provided as a series of sequential blocks. In other embodiments, the sequence of blocks may occur in another order or even in parallel. Therefore, the present invention is not limited to Figure 3A The order in which the transportation means are listed in the transportation means location diagram 301 .

[0039] The vehicle position flow chart 301 begins at block 303 where it is determined that a vehicle position is needed. This may be a need for a navigation system for the vehicle. At block 305, it is determined whether GNSS is available. Whether GNSS is available may be determined based on detection of satellite signals, known GNSS coverage areas, and known GNSS denied areas, as discussed further below. If it is determined at block 303 that GNSS is available, then at block 317, GNSS is used to determine the location of the vehicle.

[0040] If it is determined at block 305 that GNSS is not available, then it is determined at block 309 whether LPS is available. If LPS is available, then the LPS is used to determine the location of the vehicle at block 321. Determining whether LPS is available may be done based on detecting an LPS signal and a known LPS coverage area. If LPS is not available, then an alternative navigation system is used at block 313. For example, a navigation system using INS, radar, LiDAR, etc. may be used. The process then continues at block 303 when another location is needed.

[0041] Figure 3B A method of using the LPS is provided in the LPS flowchart 300 of FIG. The LPS flowchart 300 is provided as a series of sequential steps. In other embodiments, the sequence of the blocks may occur in another order or even in parallel. Therefore, the present invention is not limited to Figure 3B The LPS flow chart 300 is listed in the order.

[0042] In one embodiment, the LPS transmitter (generally represented by 104) transmits a signal encoded with a high-resolution timestamp and an identification of the LPS transmitter 104 and its position coordinates, as indicated in box 302. Each transmitter 104 may include a high-precision clock 107, which is used to generate a timestamp in the transmitted signal (LPS signal). The transmitted timestamp corresponds to the transmission time of the LPS signal. Once the LPS receiver 204 of the vehicle 100 receives the LPS signal from the LPS transmitter 104, the controller 202 reads the time on the synchronized high-resolution clock 205 at box 304 and records the receipt of the timestamp in the memory 210. In another example, the LPS receiver 204 is designed to read and record the time from the clock when the LPS signal is received. In addition, in one embodiment, at box 306, the signal is converted from an analog signal to a digital signal using an analog-to-digital converter 211. The controller 202 then processes the payload data from the received signal in digital format. When processing the payload data in the received signal, the controller 202 may implement a signal processing and data extraction function (SPF) 215 stored in the memory 210. The signal processing and data extraction function 215 is used to decode accurate timestamps and transmitter positioning information from the payload data. In addition, in one example, the controller 202, the memory 210, and the clock 205 may all be part of the LPS receiver 204.

[0043] In one example, the transmitter 104 integrates a high resolution atomic clock 107 with time and frequency division multiplexing when transmitting the LPS signal so that there is minimal interference. The transition time may be determined at a static known interval associated with each transmitter 104. At block 307, the identity of the transmitter 104 of the LPS signal may be used to verify the integrity of the signal (i.e., to avoid data from an incorrect / hacked transmitter).

[0044] In an example, a database (DB) 212 is used to maintain the identity of the transmitter 104. At block 307, the controller 202 may verify the signal received from the transmitter 104 at the LPS receiver 204 by verifying the transmitter 104 of the transmitted LPS signal. In one example, this may be accomplished by correlating the unique frequency used by the transmitter 104 with the frequency associated with the transmitter in the database 212. Validating the signal increases the integrity of the LPS by limiting the incoming signal to only predefined transmitters. At block 308, it is determined whether the signal is valid.

[0045] If it is determined at block 308 that the signal is not a valid signal, then the signal is removed or isolated at block 309 and the process continues at block 302. Additionally, in one example, if it is determined that the LPS data is unreliable (not a valid signal at block 308), then at block 311 the controller 202 implements a source selection and correction function (SSC) 219 that switches to other reliable data sources, such as position information from the INS 206. The process then continues at block 302.

[0046] If it is determined at block 308 that it is a valid signal, then at block 312 the transmitter location and transmission timestamp information received from all available valid transmitters is determined by the controller 202 implementing the signal processing and data extraction functionality 215 .

[0047] Once the controller 202 has the position and timestamp information from each valid transmitter 104, the controller 202 performs a location determination function (LDF) 217 ​​on the appropriate set of transmitter position and transmit timestamp information (i.e., transmitter position and transmit timestamp information from four or more transmitters) to determine the location of the vehicle at block 314. In one example, this is accomplished by determining the range information to each transmitter 104 using the time it takes to travel from the corresponding transmitter (i.e., subtracting the transmit time from the receive time). Basic triangulation calculations may be used to determine the location of the vehicle at a given time given the range to each of the at least four transmitters.

[0048] This position fix may be used for navigation of the vehicle, as illustrated in block 316. In one example, this is accomplished using the vehicle control system 216 based at least in part on the position information provided by the controller 202. In an example, at block 318, the position of the vehicle determined by the LPS 201 may be periodically provided to an inertial-based navigation system (in the example, the INS 206) for calibration (i.e., to correct for drift) and for calibration of other position information systems. In addition, the determination of the LPS position may be used to guide the vehicle to a GNSS coverage area (such as a GPS receiver). Figure 1 In one example, the LPS signal from the transmitter 104 includes a priority prompt to guide the vehicle 100 to at least one of a GNSS coverage area (such as the GNSS coverage area 118) and a designated stopping location (such as a vertical take-off and landing airport in a GNSS denied area 130). In addition, in one example, the LPS signal from the transmitter 104 includes a priority prompt to guide the vehicle 100 to a GNSS coverage area (such as the GNSS coverage area 118) and a designated stopping location. The controller 202 guides the vehicle 100 to the GNSS coverage area or the designated stopping location based on the operating instructions, the determined location, and the priority prompt. In one example, the priority prompt (which may include directions) guides the fixed-wing vehicle to the desired area. The fixed-wing vehicle may include a fixed-wing urban air mobility (UAM) vehicle. In this example, the UAM traffic management system may provide priority guidance prompts as part of the services provided in an area such as the LPS coverage area 120.

[0049] In one example, at block 320, the position of the vehicle based on LPS 201 is displayed on display 218 for viewing by an operator. In one example, this is accomplished by controller 202 executing instructions stored in memory 210. Controller 202 may also be configured to cause the display to illustrate GNSS denied areas and LPS coverage areas based on information and operating instructions stored in memory 210. Additionally, at block 322, LPS information (such as detection of LPS coverage areas) is communicated to a remote location. The communicated LPS information may also include the determined position of the vehicle. The process then continues at block 302.

[0050] Figure 4 The method of providing LPD transmitter information is illustrated in the transmitter information flow chart 400 of FIG. The transmitter information flow chart 400 is provided as a series of sequential blocks. In other embodiments, the sequence of blocks may occur in another order or even in parallel. Therefore, the present invention is not limited to Figure 4 The transmitter information flow chart 400 is listed in the order.

[0051] At block 402, a determination is made as to whether a path of travel has been entered. In an avionics application, this would be the flight path. At block 404, once the path of travel has been entered, a determination is made as to whether there is a GNSS denied area within the path of travel. If there is no GNSS denied area within the path of travel, the process ends at block 406.

[0052] At block 408, once it is determined that the vehicle flight path points to the GNSS denied area 130, information regarding the position coordinates of the associated LPS transmitter 104 becomes available to the LPS coverage area 120 of the controller 202. In an example, this allows the controller 202 to determine the vehicle position within the LPS coverage area 120.

[0053] The clock value is synchronized with all other transmitters 104 and receivers in the LPS. The LPS receiver 204 on the vehicle 100 can receive all LPS signals from the transmitters 104 and will be able to decode the coordinates of the transmission and the timestamp associated with the precise time of the transmission. Once the receiver 204 or the controller 202 (which may be part of the receiver 204 in the example) is able to decode the positioning, transmission time, and reception time associated with at least 4 of the transmitters 104, the travel time of the signal is calculated. Based on the travel time, the range information to each transmitter can be determined. For example, if the timestamps associated with at least four transmitters are t1, t2, t3, t4, and the timestamps associated with the reception of the received signal are tr1, tr2, tr3, t4, the distance (range) can be calculated by the formula distance = (tri-ti) × c, where c is the speed of light. By knowing the x, y, z position coordinates of the 4 transmitters with positions (xi, yi, zi) and distances di (i=1, 2, 3, 4), the vehicle position information can then be determined using the known trilateration method used in GPS.

[0054] As discussed above, some embodiments may employ an integrity check to verify that the signal received at the LPS receiver 204 of the vehicle 100 is from a valid transmitter 104 associated with the LPS 201. In one example, this is accomplished using signal strength and frequency. Figure 5 , provides an example of an integrity check positioning calculation chart 500. The integrity check positioning calculation chart 500 is based on Figure 6 The method illustrated in the positioning integrity flowchart 600 of FIG. 600 includes a series of sequential blocks. In other examples, the sequence of the blocks may occur in a different order or in parallel. Therefore, the present invention is not limited to Figure 6 in the order listed.

[0055] The process listed in the positioning integrity flow chart 600 begins at block 602, where at time TP (first time), transmitter T1 transmits a first LPS signal of intensity IP (first intensity) and frequency FP (first frequency). At block 604, at time TQ (second time), transmitter T1 transmits a second LPS signal of intensity IQ (second intensity) and frequency FQ (second frequency). In this example, the first intensity is greater than the second intensity. Figure 5 The distance D1 that the first LPS signal with strength IP (first strength) from transmitter T1 should reach is illustrated. Therefore, a vehicle receiver within the first coverage area 502 (within the range of the first LPS signal of the first strength) should be able to detect the first LPS signal of the first strength. The second LPS signal of the second strength should extend the distance indicated by D2. A vehicle receiver within the second coverage area 504 will be able to detect the second LPS signal of the second strength and the first integrity LPS of the first strength.

[0056] At block 606, it is determined whether the receiver 204 of the vehicle 100 has received T1 transmit IP-FP signals which would indicate that the vehicle 100 is in the process of receiving the T1 transmit IP-FP signals. Figure 5 The receiver is within the first coverage area 502 (or sector) set by the distance D1. If the receiver has not received the IP-FP signal, the vehicle may currently be out of range of the transmitter T1. In an example, the process may continue at block 602, where the transmitter transmits a new transmission signal of a selected strength and a selected frequency at a time interval.

[0057] If it is determined at block 606 that the receiver 204 of the vehicle 100 has received the IP-FP signal (the first LPS signal), then it is determined at block 608 whether the receiver has also received the IQ-FQ signal (the second LPS signal). If the IQ-FQ signal has not been received, then it is determined at block 610 that the vehicle 100 is within the integrity coverage area 502. However, if it is determined at block 608 that the IQ-FQ signal (the second LPS signal) has also been received, then it is determined at block 612 that the vehicle 100 is within the second integrity coverage area 504.

[0058] exist Figure 6In the example of FIG. 1 , at block 614, the determined integrity coverage area in which the vehicle is located is compared to the LPS position determined by LPS 201. If it is determined at block 616 that the LPS position is within the determined integrity coverage area, then it is determined at block 618 that the LPS position is valid. The LPS position determination may then be used for navigation of the vehicle 100. If it is determined at block 616 that the LPS position is not within the determined integrity coverage area, then it is determined at block 620 that the LPS position is invalid. The LPS position determination may then not be used for navigation of the vehicle 100. In this case, other navigation systems may be used. The process then continues at block 602.

[0059] Furthermore, in an example, by using the same transmitter T1 with multiple intensities, with the greatest possible distances D1, D2, etc., the location of the vehicle 100 can be approximated and used to isolate the divergent distance calculations. Furthermore, the process can be repeated for other transmitters as well, and no two transmitters in close proximity have the same frequency. If the distance associated with a particular transmitter is not within the possible integrity coverage area, the data can be isolated and not used to calculate the location of the vehicle by the LPS. This helps determine the integrity of the LPS signal.

[0060] Figure 7 The method of operating a vehicle is illustrated in the vehicle operation flowchart 700 of FIG. The vehicle operation flowchart 700 includes a series of sequential blocks. In other examples, the sequence of the blocks may occur in a different order or in parallel. Therefore, the present invention is not limited to Figure 7 in the order listed.

[0061] In this example, at box 702, the controller 202 uses a display (such as the display 218 of the vehicle 100) to display coverage information. The coverage information may include one or more of a GNSS enabled area, a GNSS denied area, and an LPS coverage area. In the aircraft example, the display may be a cockpit display. In another example (such as the unmanned aerial vehicle example), the display may be located at a remote location of the vehicle. In the example of the vehicle operation vehicle flow chart 600, it is determined whether the vehicle is about to leave the boundary of the GNSS enabled area. At box 704, if the vehicle is not about to leave the GNSS coverage area, the process continues to monitor the position in the GNSS coverage area.

[0062] In one example, if it is determined at block 704 that the vehicle is about to leave the GNSS coverage area (i.e., leave the boundary of the GNSS coverage area), an alert or warning is provided to the crew member (operator) of the vehicle at block 705. The warning may be in the form of an audio alert and / or a visual alert displayed on the display 218. In avionics applications, the display may be a primary flight display. In another example, another alert or warning may be provided to the crew member when it is determined that the vehicle is about to leave the LPS coverage area boundary.

[0063] Then, at block 706, navigation reference points (waypoints) are provided in the LPS coverage area (such as the LPS coverage area 120) for navigation of the vehicle. Pointing the vehicle 100 to the LPS coverage area 120 allows the vehicle 100 to obtain positioning coordinates through the LPS 201. In one example, when the vehicle 100 is about to leave the GNSS-enabled area at block 704, the cockpit display (such as the display 218 in an avionics application) highlights the LPS coverage area 120. Further, in an example, when waypoints / other reference points are available in the UAM area, waypoints can be placed within the LPS coverage area 120 to ensure that heading and navigation information is available to the vehicle.

[0064] Additionally, in one example, database 212 is used to identify and display GNSS denied areas and LPS coverage areas in the vehicle's path of travel. Figure 8 The method of generating a database and providing coverage areas to a vehicle is illustrated in the coverage area flowchart 800 of FIG. The coverage area flowchart 800 includes a series of sequential blocks. In other examples, the sequence of the blocks may occur in a different order or in parallel. Therefore, the present invention is not limited to Figure 8 in the order listed.

[0065] In this example, the coverage area flowchart 800 begins collecting coverage information at box 802. In one example, an unmanned aerial vehicle (UAV) can be used to collect coverage information. The UAV can effectively fly in an urban environment to collect three-dimensional coverage information. The coverage information may include GNSS coverage areas 118, GNSS denied areas 130, and LPS coverage areas 120. The coverage information includes the coordinates of the location where the coverage information is collected. At box 804, the coverage information is stored in a memory. In one example, the coverage information is stored in a database 212 in the memory 210. In addition, in one embodiment, the coverage information is communicated to a remote location where it is compiled and stored in a database and then distributed to other vehicles.

[0066] Then, at block 806, the controller 202 may use the stored coverage information to display coverage information (i.e., at least one of the GNSS coverage areas 118, the GNSS denied areas 130, and the LPS coverage areas 120) near or within the path of travel of the vehicle 100. In one example, the coverage information may be used to create a three-dimensional visualization of at least one of the GNSS coverage areas 118, the GNSS denied areas 130, and the LPS coverage areas 120 on the display 218. The process continues at block 802.

[0067] Fig. 9 An example of a method that the controller 202 may use to transition from GNSS to LPS when providing an overlap in coverage is illustrated in the overlap transition flowchart 900 of FIG. The overlap transition flowchart 900 includes a series of sequential blocks. In other examples, the sequence of blocks may occur in a different order or in parallel. Therefore, the present invention is not limited to Fig. 9 in the order listed.

[0068] At block 902, the vehicle uses positioning or location information from GNSS. At block 904, it is determined whether the vehicle, such as vehicle 100, is in an overlap region, such as overlap region 132. If the vehicle is not in the overlap region, the process continues at block 902 using positioning information. If it is determined at block 904 that the vehicle is in the overlap region, then at block 906 the vehicle positions from both GNSS and LPS position determinations are compared.

[0069] A determination is made at block 908 whether a match is found between the GNSS position fix and the LPS position fix. In the example, if a match is not found at block 908, the process continues at block 902. If a match is found at block 908, the position (position fix) calculation is switched to the LPS generated position information at block 910.

[0070] A determination is then made at box 912 as to whether the vehicle is still within the LPS coverage area. If it is determined that the vehicle is still within the LPS coverage area, the process continues at box 912 to monitor whether the vehicle is still within the LPS coverage area. If it is determined at box 912 that the vehicle is no longer within the LPS coverage area, a determination is made at box 914 as to whether GNSS is available. If GNSS is available, the position generated by GNSS is used at box 902 if available. If GNSS is not available, an alternative navigation system may be used at box 916 until GNSS becomes available. Alternative navigation systems using other systems such as INS 206 and other sensors 207 such as, but not limited to, altimeters, magnetic field sensors, cameras, LiDAR, radar, radio equipment, and star trackers, etc., may be used.

[0071] Furthermore, since the positions calculated by the LPS are precise and error-free as they are based on precise time atomic clocks, the LPS 201 can be used to eliminate position (fix) and computational errors in GNSS position determinations when providing overlap in coverage for safety reasons.

[0072] In an avionics example, the controller 202 of the vehicle 100 (aircraft) may use other sensors 207 (such as an altimeter) to safely ascend back into the GNSS coverage area 118 until the vehicle can again travel on its intended path. When ascending back into the GNSS coverage area 118, other sensors (e.g., radar sensors) may be used to ensure clear separation from other vehicles, buildings, terrain, etc.

[0073] In the event that there are more than one aircraft in close proximity to each other that have moved out of the LPS coverage area 120 into the GNSS denied area 130 , a method of moving the aircraft in a safe manner is needed. Fig.10 An example method for coordinating the movement of a vehicle 100 outside of LPS and GNSS is illustrated in the coordinated vehicle movement flowchart 1000 of FIG. The coordinated vehicle movement flowchart 1000 includes a series of sequential blocks. In other examples, the sequence of blocks may occur in a different order or in parallel. Therefore, the present invention is not limited to Fig.10 in the order listed.

[0074] The coordinated vehicle movement flow chart 1000 begins at block 1002. In one example, a determination is made at block 1001 whether one or more of the vehicles have priority to ascend before the other vehicles. For example, a fixed-wing aircraft may have priority over an aircraft that can hover. If it is determined that one of the vehicles has priority, then at block 1003 the vehicle is permitted to ascend to the GNSS coverage area 118.

[0075] The process continues at box 1004, where each vehicle transmits its altitude to the remote location. In the avionics example, the remote location may be an air traffic controller. At box 1006, once all altitudes are transmitted to the remote location, the remote location determines the vehicle with the maximum altitude. Then, at box 1008, the remote location permits the vehicle with the maximum altitude to ascend. The vehicle with the maximum altitude may then ascend into the GNSS coverage area 130 as directed by the relevant traffic controller. In the UAM traffic example, the relevant traffic controller may be a UAM traffic controller. Additionally, in the aircraft example, the relevant traffic controller may be an air traffic controller.

[0076] At block 1010, a vehicle with a next maximum altitude is determined. Then, at block 1012, the remote location permits the determined vehicle with the next maximum altitude to ascend. Then, the vehicle with the next maximum altitude may ascend into the GNSS coverage area 130.

[0077] At block 1014, it is determined whether there are any more vehicles outside the LPS coverage area 120 and the GNSS coverage area 118. If it is determined at block 1014 that there are more vehicles outside the LPS coverage area 120 and the GNSS coverage area 118, the process continues with determining the next vehicle with the maximum altitude at block 1010. Once all vehicles have moved out of the LPS coverage area 120 and the GNSS coverage area 118, the process ends at block 1016.

[0078] Furthermore, in an example, if the vehicle 100 is outside of the GNSS coverage area 118 and the LPS coverage area 120 , the vehicle may be directed to the GNSS coverage area 118 and the LPS coverage area 120 after a selected period of time to correct for accumulated errors. Fig.11 An example method for this is illustrated in the error correction flowchart 1100 of FIG. The error correction flowchart 1100 includes a series of sequential blocks. In other examples, the sequence of blocks may occur in a different order or in parallel. Therefore, the present invention is not limited to Fig.11 in the order listed.

[0079] At box 1102, the length of time outside of GNSS coverage areas and LPS coverage areas is tracked as the associated vehicle is traversing along a path of travel. At box 1104, a determination is made as to whether the time outside of GNSS coverage areas and LPS coverage areas has reached a set threshold. The threshold time is a set time at which a moderate accumulation of errors may occur in the vehicle position calculated without GNSS and LPS assistance. If the threshold has not been reached at box 1104, the process continues monitoring at box 1102. Once the time threshold is reached at box 1104, an alarm is generated at box 1106. The alarm warns the crew of the vehicle that they need to fly or drive the vehicle to the nearest GNSS coverage area 118 or LPS coverage area 120 to correct the error accumulation. The alarm may be an audible alarm and / or a visual alarm. An example of an alarm is Figure 2 221 of the vehicle 100 in the vehicle. Additionally, in an example, the vehicle control system 216 may be instructed to control the vehicle to the nearest GNSS coverage area 118 or LPS coverage area 120.

[0080] As discussed above, when a vehicle is outside of the GNSS and LPS coverage area, the vehicle may use other navigation systems (i.e., INS, etc.) and sensors 207 (i.e., radar, altimeter, etc.) to continue traveling on the vehicle's intended path until an error-free position calculation is available. Other navigation systems and sensors may be used to ensure that the vehicle's path of travel is clearly separated from other vehicles and buildings, terrain, etc.

[0081] Maintenance of transmitters 104 may be accomplished through the use of drones that are periodically used to verify that each transmitter is transmitting its designated LPS signal to cover the associated LPS coverage area.

[0082] Example Implementation

[0083] Embodiment 1 is a method for determining the position of a vehicle, the method comprising: when a global navigation satellite system (GNSS) receiver of the vehicle is receiving satellite signals from at least four satellites of the GNSS, using the GNSS to determine the position of the vehicle; and when the vehicle is within an LPS coverage area of ​​a local positioning system (LPS), using the LPS to determine the position of the vehicle, wherein the LPS coverage area is an area that provides LPS signals from at least four fixed-position LPS signal transmitters, each LPS signal from each LPS transmitter including transmitter position information and clock information used by a controller of the vehicle to determine the position of the vehicle.

[0084] Embodiment 2 includes the method of embodiment 1, wherein each LPS transmitter comprises an atomic clock.

[0085] Embodiment 3 includes the method of any one of Embodiments 1-2, wherein the LPS coverage area is at least partially formed in a GNSS denied area.

[0086] Embodiment 4 includes a method according to any one of embodiments 1 to 3, further comprising displaying a GNSS denied area on a vehicle display as the vehicle travels along the travel path to warn the vehicle crew that the vehicle is about to travel in the GNSS denied area.

[0087] Embodiment 5 includes the method of any one of Embodiments 1 to 4, further comprising calibrating an alternative navigation system of the vehicle using the position of the vehicle determined using the LPS.

[0088] Embodiment 6 includes the method according to embodiment 5, wherein the alternative navigation system is an inertial navigation system.

[0089] Embodiment 7 includes a method according to any one of embodiments 1 to 6, further comprising tracking the length of time the vehicle travels through the GNSS denied area to determine whether the LPS position should be used to calibrate the alternative navigation system when the vehicle enters the LPS coverage area.

[0090] Embodiment 8 includes the method of any one of Embodiments 1 to 7, further comprising using the LPS to guide the vehicle to at least one of a GNSS coverage area and a designated stopping location.

[0091] Embodiment 9 includes the method of any one of embodiments 1 to 8, further comprising performing an integrity check on the LPS position determination performed by the LPS.

[0092] Embodiment 10 includes the method of embodiment 9, wherein the integrity check of the position determination by the LPS further comprises determining the position of the vehicle relative to a first integrity coverage area and a second integrity coverage area, wherein the first integrity area is generated by an LPS transmitter transmitting a first LPS signal having a first intensity and a first frequency at a first time, the first LPS signal arriving a first distance from the LPS transmitter, and the second integrity area is generated by the LPS transmitter transmitting a second LPS signal having a second intensity and a second frequency at a second time to generate a second integrity coverage area extending a second distance from the LPS transmitter, the second integrity coverage area including a portion of the first integrity coverage area and the second integrity coverage area; and comparing the determined LPS position of the vehicle with the determined position of the vehicle relative to the first integrity coverage area and the second integrity coverage area to determine the integrity of the determined LPS position.

[0093] Embodiment 11 includes the method of any one of Embodiments 1 to 10, further comprising providing a priority prompt to guide the vehicle to at least one of a GNSS coverage area and a designated stopping location when within the LPS coverage area.

[0094] Embodiment 12 includes the method of any one of Embodiments 1 to 11, further comprising providing a warning when the vehicle approaches a boundary of at least one of a GNSS coverage area and the LPS coverage area.

[0095] Embodiment 13 includes the method according to any one of Embodiments 1 to 2, further comprising: collecting LPS coverage area information; and storing the LPS coverage area information in a database.

[0096] Embodiment 14 includes a method according to any one of Embodiments 1 to 13, further comprising: comparing the GNSS position determination with the LPS position determination when the GNSS coverage area overlaps with the LPS coverage area; and once there is a match between the GNSS position determination and the LPS position determination, using the LPS to determine the position.

[0097] Embodiment 15 includes the method according to any one of embodiments 1 to 14, further comprising: tracking the length of time that the vehicle is outside the GNSS coverage area and the LPS coverage area; and generating an alarm when the tracking time length reaches a threshold.

[0098] Embodiment 16 includes the method of any one of Embodiments 1 to 15, further comprising receiving an indication to ascend to a permitted GNSS coverage range based on the plurality of vehicles including each vehicle in the plurality of vehicles based on an altitude of the vehicle.

[0099] Embodiment 17 includes a navigation system. The vehicle position determination system includes a GNSS receiver, an LPS positioning system receiver, a memory, and a controller. The GNSS is used to receive satellite signals from multiple satellites. The LPS receiver is used to receive LPS signals from multiple fixed-position LPS transmitters, and the multiple fixed-position LPS transmitters are positioned to form an LPS coverage area. The memory is used to store at least operating instructions. The controller communicates with the GNSS receiver, the LPS receiver, and the memory. The controller is configured to use the LPS signal to determine the position of the vehicle when the vehicle is within the LPS coverage area and within the coverage area where the GNSS is denied. The LPS coverage area is an area where the LPS signals from at least four fixed-position LPS transmitters are provided. Each LPS signal from each LPS transmitter includes LPS transmitter position information and clock information used by the controller of the vehicle to determine the position of the vehicle.

[0100] Embodiment 18 includes the navigation system of Embodiment 17, wherein the controller is configured to determine the position of the vehicle using the satellite signals received by the GNSS receiver when the vehicle is in a GNSS coverage area.

[0101] Embodiment 19 includes another vehicle position determination system using LPS. The vehicle position determination system includes a display, a GNSS receiver, an LPS positioning system receiver, an INS, a memory, and a controller. The GNSS receiver is used to receive satellite signals from a plurality of satellites. The LPS receiver is used to receive LPS signals from a plurality of fixed position LPS transmitters, the plurality of fixed position LPS transmitters being positioned to form an LPS coverage area. The INS is used to determine at least a relative measurement given an initial reference. The memory is used to store at least operating instructions. The memory includes a database, the database including at least GNSS coverage areas and LPS coverage areas. The controller communicates with the GNSS receiver, the LPS receiver, the INS, the memory, and the display. The controller is configured to use the LPS signal to determine the position of the vehicle when the vehicle is within the LPS coverage area and within the coverage area where the GNSS is denied. The LPS coverage area is an area where the LPS signals from at least four fixed position LPS transmitters are provided. Each LPS signal from each LPS transmitter includes LPS transmitter position information and clock information used by the controller of the vehicle to determine the position of the vehicle. The controller is further configured to calibrate the INS using the position of the vehicle determined using the LPS.The controller is further configured to display the GNSS coverage area and the LPS coverage area stored in the database using the display.

[0102] Embodiment 20 includes the vehicle position determination system of embodiment 19, wherein the controller is configured to track the length of time the vehicle is outside of the GNSS coverage area and the LPS coverage area, and to generate an alert when the tracked time reaches a threshold.

[0103] Although specific embodiments have been illustrated and described herein, one of ordinary skill in the art will recognize that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any modifications or variations of the present invention. Therefore, it is apparent that the present invention is limited only by the claims and their equivalents.

Claims

1. A method for determining a position of a vehicle (100), the method comprising: determining the position of the vehicle (100) using a global navigation satellite system (GNSS) receiver (208) of the vehicle (100); when the GNSS receiver (208) of the vehicle (100) is receiving satellite signals from at least four satellites (102) of the GNSS; as well as When the vehicle (100) is within a local positioning system (LPS) (201) coverage area (120), the position of the vehicle (100) is determined using the LPS (201), wherein the LPS coverage area (120) is an area that provides LPS signals from at least four fixed-position LPS signal transmitters (104), each LPS signal from each LPS transmitter (104) including transmitter position information and clock information used by a controller (202) of the vehicle (100) to determine the position of the vehicle (100).

2. A navigation system (101), the navigation system comprising: a global positioning satellite system (GNSS) receiver (208) for receiving satellite signals from a plurality of satellites (102); a local positioning system (LPS) receiver (204) for receiving LPS signals from a plurality of fixed-location LPS transmitters (104) positioned to form an LPS coverage area (120); A memory (210), the memory being used to store at least an operation instruction; and A controller (202) in communication with the GNSS receiver (208), the LPS receiver (204), and the memory (210), the controller (202) being configured to use the LPS signal to determine the position of the vehicle (100) when the vehicle (100) is within the LPS coverage area (120) and within a GNSS denied coverage area (130); wherein the LPS coverage area (120) is an area providing the LPS signals from at least four fixed position LPS transmitters (104), each LPS signal from each LPS transmitter (104) including LPS transmitter position information and clock information used by the controller (202) of the vehicle (100) to determine the position of the vehicle (100).

3. A vehicle position determination system (101), the vehicle position determination system using a local positioning system (LPS) (201), the vehicle position determination system (101) comprising: Display (218); a global positioning satellite system (GNSS) receiver (208) for receiving satellite signals from a plurality of satellites (102); a local positioning system (LPS) receiver (204) for receiving LPS signals from a plurality of fixed-location LPS transmitters (104) positioned to form an LPS coverage area (120); an inertial navigation system (INS) (206) for determining at least relative measurements given an initial reference; a memory (210), the memory being configured to store at least operating instructions, the memory (210) comprising a database (212), the database comprising at least GNSS coverage areas (118) and LPS coverage areas (120); and a controller (202) in communication with the GNSS receiver (208), the LPS receiver (204), the INS (206), the memory (210), and the display (218), the controller (202) being configured to determine the position of the vehicle (100) using the LPS signal when the vehicle (100) is within the LPS coverage area (120) and within a GNSS denied coverage area (130); wherein the LPS coverage area (120) is an area providing the LPS signal from at least four fixed position LPS transmitters (104) , each LPS signal from each LPS transmitter (104) includes LPS transmitter position information and clock information used by the controller (202) of the vehicle to determine the position of the vehicle (100), the controller (202) being further configured to calibrate the INS 206 using the position of the vehicle (100) determined using the LPS (201), the controller (202) being further configured to use the display (218) to display the GNSS coverage area (118) and the LPS coverage area (120) stored in the database (212).

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