Satellite Signal Spoofing Detection System

A satellite spoofing signal detection system with at least one primary antenna installed on a top side of a vehicle body, at least one secondary antenna installed on a bottom side of the vehicle body, and a spoofing controller is provided. The spoofing controller is configured to determine if a spoofing signal is present by comparing primary satellite signals received by the at least one primary antenna and secondary satellite signals received by the at least one secondary antenna. The spoofing controller determines if a spoofing signal is present by comparing a number of satellites used in position computations along with protection limits determined by the primary satellite signals and the secondary satellite signals. Other information from the primary and secondary antennas, such as visible satellites, receiver autonomous integrity monitoring, dilution of precision, and satellite almanac information may be used to determine if a spoofing signal is present.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Indian Application No. 202311006533 filed on Feb. 1, 2023, same title herewith, the contents of which are incorporated herein in its entirety.

BACKGROUND

A recent threat to the accuracy of information from Global Navigation Satellite System (GNSS) receivers comes from spoofing. Spoofing occurs when signals, not originating from satellites, are inadvertently processed by the GNSS receiver as satellite signals. This may lead the GNSS receiver to output erroneous position outputs decoded from the received signals.

In an aircraft application, GNSS receiver outputs may be consumed by multiple aircraft critical systems including automatic dependent surveillance-broadcast (ADS-B), enhanced ground proximity warning system (EGPWS), terrain avoidance and warning system (TAWS), Flight Controls etc. Further, required navigation performance (RNP) may be deteriorated due to spoofing.

Incorrect information from the GNSS receivers caused by spoofing can result in an aircraft being off tracked from a desired travel path. This may result in a catastrophic event. Aircraft are especially vulnerable to a catastrophic event when spoofing occurs during an aided landing operation that uses positioning data from a GNSS receiver. Examples of aided landing systems that may use satellite signals to aid in landing include ground-based augmentation system (GBAS) landing system (GLS), satellite-based augmentation system (SBAS), and localizer performance with vertical guidance (LPV) systems.

Spoofing signals, either generated by a bad actor or other unintentional source, are typically transmitted from a ground source and are generally more effective when an aircraft is at lower altitude. At lower altitudes, the signal strength from spoofing signals generated from the ground is relatively strong making it more likely to be locked/processed by a GNSS receiver as if the spoofing signals are from GNSS satellites.

Further, spoofing signals broadcast from the ground can impact multiple aircrafts traveling in a coverage area of the spoofing signals. This can lead to plurality aircraft receiving incorrect position information which increases the probability of aircraft-to-aircraft collisions.

Spoofing is not only an issue for traditional aircraft but also unmanned aerial vehicles (UAVs)/urban air mobility (UAM) as well as other air/sea/land vehicles.

For the reasons stated above and for other reasons stated 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 an effective and efficient spoofing threat detection system to ensure received satellite signals are accurate and reliable.

SUMMARY

The following summary is made by way of example and not by way of limitation. It is merely provided to aid the reader in understanding some of the aspects of the subject matter described. Embodiments provide a satellite signal spoofing detection system that effectively and efficiently determines if a spoofing signal is present with the use of a primary antenna and at least one secondary antenna. Primary information determined from the primary antenna is compared with secondary information determined from the at least one secondary antenna is compared in determining if spoofing signals are present.

In one embodiment, a satellite spoofing signal detection system is provided. The system includes at least one primary antenna installed on a top side of a vehicle body, at least one secondary antenna installed on a bottom side of the vehicle body, and a spoofing controller. The spoofing controller is configured to determine if a spoofing signal is present by comparing primary satellite signals received by the at least one primary antenna and secondary satellite signals received by the at least one secondary antenna. The spoofing controller determines if a spoofing signal is present by comparing at least one of a number of satellites used in position computations along with protection limits and a number of visible satellites determined by the primary satellite signals and the secondary satellite signals.

In another embodiment, a method of detecting a spoofing signal is provided. The method includes receiving primary satellite signals from a primary antenna and secondary satellite signals from at least one secondary antenna, wherein the primary antenna is mounted on a top side of a vehicle than the at least one secondary antenna is mounted on a bottom side of the vehicle; and comparing primary information from the primary satellite signals and secondary information from the secondary satellite signals in determining if a spoofing signal is present in one of the primary satellite signals and the secondary satellite signals, wherein the primary information and the secondary information includes a number of satellites used in position computations along with protection limits.

In yet another embodiment, another method of detecting a spoofing signal is provided. The method includes receiving primary satellite signals from a primary antenna and secondary satellite signals from at least one secondary antenna, wherein the primary antenna is mounted on a top side of a vehicle and the at least one secondary antenna is mounted on a bottom side of the vehicle; and comparing primary information from the primary satellite signals and secondary information from the secondary satellite signals in determining if a spoofing signal is present in one of the primary satellite signals and the secondary satellite signals, wherein the primary information and the secondary information includes a number of visible satellites.

DETAILED DESCRIPTION

Embodiments of the present invention provide a satellite signal spoofing detection system. In examples, two spaced satellite signal antennas are used. Information obtained from signals received at the antennas are processed and compared to determine if a spoofing signal is present. In one example, at least one primary global positioning satellite (GPS) antenna is installed on top (upper portion) of an aircraft body and at least one secondary GPS antenna is installed on a belly (lower portion) of the aircraft body. A spoofing controller is configured to determine if a spoofing signal is present by comparing primary information derived from satellite signals received by the primary GPS antenna (primary antenna) and secondary information derived from satellite signals received by the at least one secondary GPS antenna (secondary antenna). In one example, the spoofing controller determines if a spoofing signal is present by comparing primary and secondary information relating to a number of satellites used in position computations along with protection limits determined by the primary satellite signals and the secondary satellite signals.

A block diagram of a satellite signal spoofing detection system100of an example is illustrated inFIG.1. This example includes a spoofing controller102that is in communication with one or more receivers106. The one or more receivers106are in communication with antennas101-1through101-n. The antennas may be generally referenced by101. In one example there is an antenna101for each receiver106. In another example one receiver106is in communication with a plurality of antennas101.

The spoofing controller102is further in communication with a memory108. The memory108includes operating instructions implemented by the spoofing controller102as well as past signal information received from the plurality of antennas101. The spoofing controller102, based on received primary and secondary information determines if a spoofing signal has been detected. In one example the spoofing controller102then provides control signals to a vehicle control system110used to control operations of a vehicle incorporating the satellite signal spoofing detection system100.

In general, the spoofing controller102may include any one or more of a processor, microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field program gate array (FPGA), or equivalent discrete or integrated logic circuitry. In some example embodiments, the spoofing controller 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, as well as other discrete or integrated logic circuitry. The functions attributed to the spoofing controller102herein may be embodied as software, firmware, hardware or any combination thereof. The spoofing controller102may be part of a system controller or a component controller. Further the spoofing controller102may be part of a receiver106. The memory108may include computer-readable operating instructions that, when executed by the spoofing controller provides functions of the satellite signal spoofing detection system100. Such functions may include the functions of determining if a spoofing signal is present described below. The computer readable instructions may be encoded within the memory108. Memory108is an appropriate non-transitory storage medium or media including any volatile, nonvolatile, magnetic, optical, or electrical media, such as, but not limited to, a random-access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, or any other storage medium.

The satellite signal spoofing detection system100may further include a communication unit114that is designed to communicate information relating to the detection of a spoofing signal to a remote location so the information may be used by other vehicles. For example, whenever a spoofing signal is detected, an alert, such as a spoofing alert, may be generated by the spoofing controller102and broadcasted by the communication unit114to a spoofing database which may be in a centralized location, such as a cloud, so that vehicles with access to the resource database that are in a close geographical location to where the spoofing signal was detected can take appropriate measures to mitigate the spoofing signals. In one example, spoofing detection may be broadcast by the communication unit114in real time. In another example, a spoofing detection may be store in the memory108and broadcast at a later time. The memory108may include its own spoofing database that includes determined spoofing signal information that may be used to broadcast spoofing information at a later time as well as for vehicle operations.

An example of a vehicle implementing a satellite signal spoofing detection system100is an aircraft, such as aircraft202ofFIG.2. In the aircraft202example receivers106, such as GNSS receivers, are fed with GNSS signals, or satellite signals, received from active antennas204and206. Typically, at least one antenna204(the primary antenna) is installed at upper body portion of the aircraft202to ensure satellites visibility. As illustrated inFIG.2, the visible satellites include satellites208-1through208-n. Further the upper antennas204are normally installed on the upper portion of the aircraft so that GPS satellites visibility is ensured above 15 degrees211above horizon212.

In this embodiment, additional antenna206(secondary antenna), or secondary antennas, are installed on a lower portion of the body, or belly, of the aircraft202. A ground plate, where antenna206is mounted on the belly of the aircraft, facilitates very low signal reception or no reception (where sky visibility is absent) for the signals coming from the satellites208-1through208-n. Accordingly, antenna204on the top portion of aircraft has better visibility and reception of the satellite signals from the satellites208-1and208-n. This arrangement may lead to around 30 dB or better signal attenuation at the bottom belly of aircraft202compared to antenna installed on top of the aircraft202relating to satellite signals generated by satellites208-1through208-n. This is illustrated inFIG.2, where satellite signals207afrom satellites208-1through208-nreceived at the upper antenna204are shown as solid lines (stronger signals) while satellite signals207breceived at the lower antenna206are shown with dashed lines (weaker signals).

FIG.2further illustrates spoofing signals209aand209bgenerated from a transmitter210that is located on the ground221. As illustrated, signals209areceived at the lower antenna206may be stronger than signals209areceived at the upper antenna204, provided the aircraft202is generally flying in a straight path when spoofing signals are detected.

Signals received by antennas204and206from the top and belly of the aircraft202may be fed to a dual GPS engine/receiver for position solution and monitoring, such as receiver(s)106and spoofing controller102discussed above. The configuration of the plurality of spaced antennas allows for monitoring of at least primary and secondary information derived from signals received at the antennas which may be used for determining spoofing. For example, the primary and secondary information may include signal strength information and other information. Satellite signals207areceived at the primary antenna204mounted on the upper body of aircraft202should have signal strength at least 20 to 30 dB stronger than the similar satellite signals207breceived by the secondary antenna206placed at belly of aircraft202in normal operations. If the strength of the signals at the primary antenna204is not stronger than the strength of the signals received at the secondary antenna, a spoofing signal may be present. Hence, the primary and secondary information may relate to received signal strength.

In another example, the primary and secondary information may include the number of visible satellites208-1through208-n. A satellite is visible if its signals are received by an antenna. The number of visible satellites should be higher for the upper antenna204compared to lower antenna206under normal conditions. The primary and secondary information relating to the number of visible satellites may also be used to determine if a possible spoofing signal is present. For example, if the information relating to the visible satellites indicates more satellites are visible at the secondary antenna than the primary antenna (or more than should be visible compared to the primary antenna) a spoofing signal may be present.

Other types of primary and secondary information may also be used in detecting if a spoofing signal is present as discussed further below. The spoofing controller102may generate a spoofing detection alert signal that may be used, for example, by the vehicle control system110to control operations of the vehicle and/or it may be communicated to a remote location through the communication unit114so other vehicles can be warned of the spoofing signal.

Another example of an avionic vehicle is a UAV302implementing a satellite signal spoofing detection and correction system100is illustrated inFIG.3. In the UAV example, receivers106, are fed with satellite signals received from antennas304and306. Here again, at least one antenna304(primary antenna) is installed at upper body of the UAV302to ensure satellites visibility. As illustrated inFIG.3, the visible satellites include satellites308-1through308-n. Antenna304is normally installed on the upper side of a UAV302so that the GPS satellites visibility is ensured usually 15 degree311above horizon312.

In this embodiment, additional antenna306(secondary antenna), or antennas, are installed on the bottom portion or belly of the UAV302. In this example, a ground plate305(or mounting plate) may also be used to couple the antenna306to the UAV302. The ground plate305may be used to facilitate a very low signal reception (reduce satellite signal strength) or no reception (where sky visibility is absent) for the signals coming from the satellites308-1through308-nby reducing the strength or totally stopping satellites signals incident on the ground plates305. The result allows antenna304on the top of UAV302have better visibility and reception of the satellite signals from the satellites308-1and308-nthan antenna306mounted on the bottom portion of the UAV. In one example the ground plate305is made from aluminum. This configuration may lead to around 30 dB or better signal attenuation from the satellite signals at antenna306compared to the satellite signal strength at antenna304.

Satellite signal strength at the antennas304and306are illustrated inFIG.3, where primary satellite signals307afrom satellites308-1through308-nreceived at the upper antenna304are shown as solid lines (stronger signals) while secondary satellite signals307breceived at the lower antenna306are shown with dashed lines (weaker signal).

FIG.3further illustrates spoofing signals309aand309bgenerated from a transmitter310that is located on the ground321. As illustrated, signals309areceived at the lower antenna306may be stronger than signals309areceived at the upper antenna304, provided the UAV302is in a horizontal flying position when spoofing signals are detected.

Satellite signals received by antennas304and306may be feed to dual GPS engines/receivers for position solution and monitoring, such as receiver(s)106and spoofing controller102discussed above. In one example, the spoofing controller102is located in the receiver106and compares primary and secondary information to detect any anomaly that could indicate spoofing signals are present as discussed below.

In an application of the satellite signal spoofing detection system100with dual antennas in aerial vehicles, the aerial vehicles orientation in relation to the ground321may need to be taken into consideration. For example, a high bank angle of the vehicle may influence the number of satellites seen by the antennas304and306. In particular, a high bank angle may reduce the number of satellites seen (and may reduce satellite signal strength) at the primary antenna304and increase the number of satellites seen (and may increase satellite signal strength) at the secondary antenna306. This may be more applicable to UAV than commercial aircraft that transports people where high bank angles are unlikely to be used.

FIGS.4A,4B, and4Cillustrates an example satellite signal spoofing detection and correction flow diagram400implemented by the spoofing controller102. Flow diagram400is provided as a series of sequential blocks. The sequence of blocks may occur in a different order or in parallel in other examples. Hence, embodiments are not limited to the sequence set out in flow diagram400. Further the satellite signal spoofing detection and correction flow diagram400provides different types of primary information obtained from the primary satellite signals and secondary information obtained from the secondary satellite signals in determining if a spoofing signal is present. Not all of the types of information discussed, or combinations of information discussed, needs to be used in determining if a spoofing signal is present in examples.

Referring toFIG.4A, satellite signals received or detected at a primary antenna and a secondary antenna (such as primary antenna304and secondary antenna306ofFIG.3) is processed. At block402a received signal strength indicator (RSSI) for each received signal at the secondary antenna306is determined and at block404the RSSI for each received signal at the primary antenna304is determined. At block406, a determining function is used to determine if RSSI of the received signals from the primary antenna304is greater than the RSSI of the received satellite signals from the secondary antenna306. If it is determined at block406that the RSSI of the received signals from the primary antenna304is not greater than the RSSI of the received satellite signals from the secondary antenna306, a determining function output signal relating to the RSSI information is sent to a GNSS spoof detection block420. If it is determined at block406that the RSSI of the received signals from the primary antenna304is greater than the RSSI of the received satellite signals from the secondary antenna306, the process continues monitoring the RSSI at blocks402and404.

The GNSS spoof detection block420gathers output signals from different determining functions, such as described in block406, as well as blocks410,412,422and428described below, in determining if a spoofing detection alert signal should be generated that would be used, for example, by the vehicle control system110or would be communicated to a remote location through the communication unit114. Determining when a spoofing detection alert signal should be generated may vary. For example, one output signal from one determining function that indicates a spoofing signal may be present may be enough to generate a spoofing detection alert signal and, in another example, signals from more than one determining function may be required before a spoofing detection alert signal is generated. In one example, determining functions may be weighted where heaver weighting determining functions may require less (if any) other determining function output signals in determining to generate a spoofing detection alert signal. Further output signals from determining functions with lower weighting determining functions may require further outputs from one or more determining function to verify a spoofing detection alert signal should be generated. An example of a GNSS spoof detection block402that uses a weighted system is described below in regard toFIG.5.

The number of visible satellites by the primary antenna304is determined at block408and the number of visible satellites by the secondary antenna306is determined at block409. In an example, this is done by counting the satellite signals from different satellites received at the respective antennas304and306. At block410it is determined if the number of visible satellites at the primary antenna304is greater than the number of visible satellites at the secondary antenna306. If the number of visible satellites at the primary antenna304is not greater than the number of visible satellites at the secondary antenna306, a determining function output signal relating to the visible satellite information is provided to block420where it is determined if a spoofing detection alert signal should be generated. As discussed above, in at least one example more than one type of information from more than one determining function output signal may be used before a spoofing detection alert signal is generated at block420. If it is determined that the number of visible satellites at the primary antenna304is greater than the number of visible satellites at the secondary antenna306at block410, the process continues monitoring for the number of visible satellites at blocks408and409.

At block412, a position and associated protection limit computation with the satellite signals from the primary antenna304is determined and at block414and a position and protection limit computation with the satellite signals from the secondary antenna306is determined as illustrated inFIG.4B. A receiver protection limit is a protection level that describes a region that is assured to contain the receiver's position. The protection limit is a maximum likely position error to a specified degree of confidence. If, for example, a GNSS receiver determines its position with a 95 percent protection level of one meter, there is only a 5 percent chance that reported position is more than one meter away from its true position.

At block416it is determined if the position computation and protection limit from the satellite signals from the primary antenna304is equal to the position computation and protection limit from the satellite signals from the secondary antenna306. If the position computation and protection limit from the satellite signals from the primary antenna304is not equal to the position computation and protection limit from the satellite signals from the secondary antenna306, a determining function output signal relating to the position and protection limit information is sent to block420. If the position computation and protection limit from the satellite signals from the primary antenna304is equal to the position computation and protection limit from the satellite signals from the secondary antenna306, the process continues monitoring the position and protection limits at blocks412and414.

Further in an example, the primary and secondary information may include an indication from a receiver autonomous integrity monitoring (RAIM) function or system. A RAIM system detects faults with the use of redundant pseudorange measurements when more satellites are available then needed. In the system, redundant pseudorange measurements based on signals from different satellites are compared with each other. If pseudorange measurements differ significantly from an expected value, it may indicate that a spoofing signal is present.

At block418RAIMSAinformation is determined for signals received at the secondary antenna306and at block421RAIMPAinformation is determined for signals received at the primary antenna304. At block422it is determined if either of the RAIMSAor RAIMPAinformation indicates a spoofing signal may be present. If it is determined that a difference between redundant pseudorange measurements, at one or more of the antennas304and306, is greater than expected at block422, a determining function output signal relating to the RAIM information is sent to block420. If it is determined that a difference between redundant pseudorange measurements, at one or more of the antennas304and306, is not greater than expected, the RAIM information is continued to be monitored at blocks418and421.

Further dilution of precision (DOP) information may also be looked at to determine if a spoofing signal is present. DOP information relates to the monitoring of relative satellite-antenna (receiver) geometry based on received satellite signals from different satellites at an antenna. When receiving satellites signals are from satellites that are spread out a good geometric DOP is observed with a low DOP value. When the receiving satellites signals are from satellites that are close together a weak geometric DOP is observed with a high DOP value. Spoofing signals will affect the DOP value which my lead to a determination that a spoofing signal is present. In one example, the DOP value from signals received at the primary antenna304is compared to the DOP value from signals received at the secondary antenna306.

At block424, DOPSAinformation is determined for signals received at the secondary antenna306and at block426, DOPPAinformation is determined for signals received at the primary antenna304. At block428it is determined if the DOPSAis equal to the DOPPA. If the DOPSAis not equal to the DOPPAa spoofing signal may have been detected and a determining function output signal relating to the DOP information is sent to block420. The process then continues at blocks402and404computing RSSI.

As illustrated inFIG.4C, the primary and secondary information may include satellite almanac information. Satellite almanac information relates to digital schedule of satellite parameters used for such things as providing a necessary correction factor to relate GPS time to coordinated universal time (UTC). Further, one major role of the almanac information is to help a GNSS receiver acquire satellite signals from a cold or warm start by providing data on which satellites will be visible at any given time together with approximate positions. At block430, ALMINACPAis determined and at block432, ALMINACSAis determined. At block436it is determined if the ALMINACPAinformation is equal to ALMINACSAinformation. If it is determined at block436the ALMINACPAinformation is equal to ALMINACSAthe process continues monitoring primary and secondary almanac information at blocks430and432. However, it is determined at block436the ALMINACPAinformation is not equal to ALMINACSA(or varies above a threshold set) a spoofing signal may have been detected and a determining function output signal relating to the almanac information is sent to block420.

FIG.5illustrates a flow diagram example of a spoofing detection alert signal generation method implemented by block420. The flow diagram of block420is provided as a series of sequential blocks. The sequence of blocks may occur in a different order or in parallel in other examples. Hence, embodiments are not limited to the sequence set out in flow diagram400.

As discussed above, each determining function output signal generated by blocks406,410,416,422,428, and436may be assigned their own unique weight based on how likely the determining function output signal indicates a spoofing signal is present. At block502, each determining function output signal is received and assigned a weight based on how likely the determining function output signal indicates a spoofing signal is present. At block504an assigned weight determined at block502is added to any previous weights from determining function output signals (if any). At block506it is then determined if the weight is above a threshold. If it is determined at block506the weight is not above the threshold, the process continues at block502assigning a weight to a next determining function output signal received at block502.

If it is determined at block506the weight (combined or not) is above the threshold, a spoofing detection alert signal is generated at block508. The process then continues at block509clearing the weights and then to block502looking for the next determining function output signal indicating a spoofing signal is present.

Although, the above examples discuss aeronautical vehicles, other types of vehicles including land and water vehicles using satellite signals may use this technology to detect spoofing signals.

Example Embodiments

Example 1 is a satellite spoofing signal detection system. The system includes at least one primary antenna installed on a top side of a vehicle body, at least one secondary antenna installed on a bottom side of the vehicle body, and a spoofing controller. The spoofing controller is configured to determine if a spoofing signal is present by comparing primary satellite signals received by the at least one primary antenna and secondary satellite signals received by the at least one secondary antenna. The spoofing controller determines if a spoofing signal is present by comparing at least one of a number of satellites used in position computations along with protection limits and a number of visible satellites determined by the primary satellite signals and the secondary satellite signals.

Example 2 includes the system of Example 1, wherein the spoofing controller further determines if a spoofing signal is present by comparing a signal strength between the primary satellite signals and the secondary satellite signals.

Example 3 includes the system of any of the Examples 1-2, wherein the top side of the vehicle is an upper body portion of an aircraft and the bottom side of the vehicle is a lower body portion of an aircraft.

Example 4 includes the system of any of the Examples 1-3, further including a spoofing database configured to store at least operating instructions implemented by the spoofing controller and past signal information received from the at least one primary antenna and at least one secondary antenna.

Example 5 includes the system of any of the Examples 1-4, wherein the spoofing controller further determines if a spoofing signal is present by comparing receiver autonomous integrity monitoring (RAIM) information with expected RAIM information.

Example 6 includes the system of any of the Examples 1-5, wherein the spoofing controller further determines if a spoofing signal is present by comparing a dilution of precision (DOP) determined by the primary satellite signals and the secondary satellite signals.

Example 7 includes the system of any of the Examples 1-6, further including a communication unit in communication with the spoofing controller. The communication unit configured to communicate information relating to a spoofing signal determined by the spoofing controller to a remote location.

Example 8 includes the system of any of the Examples 1-7, further including a vehicle control system configured to control operations of the vehicle. The vehicle control system in communication with the spoofing controller. The vehicle control system configured to control operations of the vehicle based at least in part on communications from the spoofing controller.

Example 9 includes the system of Example 8, wherein the vehicle control system is configured to at least mitigate position computations used to control operations of the vehicle when the spoofing controller determines a spoofing signal is present.

Example 10 includes the system of any of the Examples 1-9, wherein the spoofing controller further determines if a spoofing signal is present by comparing satellite almanac information in the primary satellite signals and the secondary satellite signals.

Example 11 includes a method of detecting a spoofing signal. The method includes receiving primary satellite signals from a primary antenna and secondary satellite signals from at least one secondary antenna, wherein the primary antenna is mounted on a top side of a vehicle than the at least one secondary antenna is mounted on bottom side of the vehicle; and comparing primary information from the primary satellite signals and secondary information from the secondary satellite signals in determining if a spoofing signal is present in one of the primary satellite signals and the secondary satellite signals, wherein the primary information and the secondary information includes a number of satellites used in position computations along with protection limits.

Example 12 includes the method of Example 11, wherein the primary information and secondary information further includes at least one of signal strength and a number of visible satellites.

Example 13 includes the method of any of the Examples 11-12, wherein the primary information and the secondary information further includes receiver autonomous integrity monitoring (RAIM) information.

Example 14 includes the method of any of the Examples 11-13, wherein the primary information and the secondary information further includes dilution of precision (DOP) information.

Example 15 includes the method of any of the Examples 11-14, further including communicating information regarding a determined spoofing signal to a remote location.

Example 16 includes the method of any of the Examples 11-15, further including controlling operations of a vehicle based at least in part on a determined spoofing signal.

Example 17 includes the method of any of the Examples 11-16, further including considering a bank angle of the vehicle when determining primary information and secondary information.

Example 18 includes method of detecting a spoofing signal. The method includes receiving primary satellite signals from a primary antenna and secondary satellite signals from at least one secondary antenna, wherein the primary antenna is mounted on a top side of a vehicle and the at least one secondary antenna is mounted on a bottom side of the vehicle; and comparing primary information from the primary satellite signals and secondary information from the secondary satellite signals in determining if a spoofing signal is present in one of the primary satellite signals and the secondary satellite signals, wherein the primary information and the secondary information includes a number of visible satellites.

Example 19 includes the method of Example 18, wherein the primary information and the secondary information further includes at least one of receiver autonomous integrity monitoring (RAIM) information, dilution of precision (DOP) information, satellite almanac information, number of satellites used in position computations, protection limits associated with the position computations and signal strength.

Example 20 includes the method of any of the Examples 18-19, further including communicating information relating to a determined spoofing signal to a remote location.