CROSS-REFERENCE TO RELATED APPLICATIONS

[001] This application claims the benefit of U.S. Provisional Application No. 62/294,083 filed on February 1 1 , 2016, the contents of which are hereby incorporated by reference.

TECHNICAL FIELD

[002] The present invention relates general to determination of relative velocity and direction of two vehicles and more particularly to providing collision alerts with respect of these vehicles.

BACKGROUND

[003] Determination of a position of a vehicle is now well-known in the art. Use of the global navigation satellite system (GNSS) allows for high accuracy determination of the position and velocity of a vehicle on the ground. The concept is used frequently in vehicle navigational system in conjunction with maps from a variety of resources. A fine example for such capabilities is presented by Waze® mobile in its navigation system that uses the combination of maps and GNSS information to accurately allow for navigation of a moving vehicle (Waze is a registered trademark of Waze Mobile Ltd.). By providing information over a data link information about other vehicles is also provided and allows the determination of, for example, traffic load on certain routes and allowing traffic congestion avoidance. However, that solution does not provide information regarding an imminent collision between two vehicles having a collision path.

[004] A traffic collision avoidance system (TCAS) provides traffic collision measures for aircrafts and designed to avoid mid-air collisions. It operates independent of air traffic control. Each plane equipped with an airborne TCAS is capable of interrogating other similarly equipped aircrafts and building a three-dimensional view of the sky around the aircraft with a preference to the direction towards which the aircraft is heading. Upon determination that a collision may occur between two aircrafts both pilots are alerted to take corrective action that will bring the aircrafts away from the collision path. This system requires that both aircrafts are equipped with TCAS in order to make the necessary determination. The TCAS involves the use of active radar components, that is, components that both transmit and receive.

[005] US patent 7,840,355 by Breed et al. (hereinafter the '355 patent) describes and accident avoidance system and methods. According to that patent, "a host vehicle includes a global positioning system residing on the host vehicle for determining the host vehicle's location as the host vehicle travels, a communication system residing on the host vehicle operative to receive signals including information received directly from other vehicles indicating the locations thereof and traffic information received from an infrastructure-based station indicating the locations of other vehicles, and a navigation system residing on the host vehicle coupled to the global positioning system and the communication system." Therefore this system requires that each vehicle provide the necessary information to some base station where such information is integrated and disseminated to other vehicles. Such a system of course does not attend to vehicles that do not provide the information to the base station, or when, for whatever reason, the information is not made available to the vehicle due, for example, to a communication failure.

[006] One of ordinary skill in the art would readily appreciate that fatalities and injuries due to vehicle collision is of high concern. It has both impact on the persons involved in the accident as well as on society resources, for example, hospitals and rehabilitation centers. It is therefore that much emphasis is put into providing both passive and active safety measures in the vehicles. One direction is the autonomous vehicle that is equipped with technology that is aware of its immediate surroundings in order to avoid impact. Nonetheless, not all vehicles in the near future are going to be autonomous vehicles and even those may need an additional layer of precaution, especially as operational speeds increase.

[007] Therefore, it would be advantageous to provide a system and methods thereof that can provide alerts and/or actions respective of a potential collision between vehicles that is independent of the capabilities of at least one of the vehicles. It would be further advantageous if such a system could avoid the need to send signals from the vehicle for the purpose of determination of a position of another object.

BRIEF DESCRIPTION OF THE DRAWINGS

[008] The subject matter disclosed herein is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the disclosed embodiments will be apparent from the following detailed description taken in conjunction with the accompanying drawings.

[009] Figure 1 A is an illustration of a junction demonstrating a potential collision path for two vehicles.

[0010] Figure 1 B is an illustration of the junction when at least one of the vehicles is equipped with a system according to an embodiment.

[0011] Figure 2 is a schematic block diagram of a system for determination of potential collision paths according to an embodiment.

[0012] Figure 3 is a flowchart of the operation of the system for determination of potential collision paths according to an embodiment.

[0013] Figure 4 is a schematic diagram for the purpose of calculation of a potential collision between two vehicles without the use of a digital map.

[0014] Figure 5 is a schematic diagram for the purpose of calculation of a potential collision between two vehicles with the use of a digital map.

[0015] Figure 6 is a flowchart for the calculation of a potential collision between two vehicles without the use of a digital map.

[0016] Figure 7 is a flowchart for the calculation of a potential collision between two vehicles with the use of a digital map.

DETAILED DESCRIPTION

[0017] It is important to note that the embodiments disclosed herein are only examples of the many advantageous uses of the innovative teachings herein. In general, statements made in the specification of the present application do not necessarily limit any of the various claimed embodiments. Moreover, some statements may apply to some inventive features but not to others. In general, unless otherwise indicated, singular elements may be in plural and vice versa with no loss of generality. In the drawings, like numerals refer to like parts through several views.

[0018] In today's environment where multiple vehicles are roaming the roads, the risk of being involved in an accident has increased. Safety precautions installed in cars, reduce the impact on the passengers; however, a better way to mitigate risk is to provide collision alerts and avoidance. Accordingly, a system is installed in a vehicle comprising a first antenna, the first antenna receiving signals from one or more global navigation satellite system (GNSS) satellites to determine the attitude, e.g., velocity and direction, of the vehicle, which may include Doppler shift and pseudo-range (based on code or phase) determinations. A second antenna receives signals from the GNSS satellites deflected from another vehicle. Respective of the signals received, a determination whether the two vehicles are in a collision path is made, and providing a respective alert or action. In one embodiment, a digital map is further used to more accurately make the collision determination.

[0019] Fig. 1 A is an illustration of a junction 100 demonstrating a potential collision path for two vehicles. The junction 100 comprises of two roads, a first road 101 and a second road 102 that intersect. On road 101 there is a vehicle 1 10 moving at a velocity Vi into the intersection of road 101 and road 102. At the same time a vehicle 120 moving at a velocity V2 in direction of that intersection. If no driver takes notice and changes the speed, increases or decreases, the vehicles 1 10 and 120 will collide at point 103. The reason that drivers of either vehicles 1 10 or 120 do not take preventive actions are many and may include but are not limited to not paying attention to what is happening on the road, obstacles, weather conditions and low-lighting that impair viewing an approaching vehicle, misjudgment of the situation and more.

[0020] Fig. 1 B is an illustration of the same junction when at least one of the vehicles, for example vehicle 1 10, is equipped with a system according to an embodiment. The system on vehicle 1 10 establishes the velocity and direction of the vehicle 1 10 respective of signals 132 received directly from GNSS satellite 130, and as further explained in greater detail herein below. The reception of the signals 132 is done by an antenna, for example antenna 1 14, directed to receive essentially signals from the vertical position, i.e., overhead of the vehicle 1 10. A second antenna, for example antenna 1 16, is directed to receive essential signals in an horizontal direction, aiming at receiving signals from the same GNSS satellite 130, for example signals 134, which may deflect as signal 136 from the second vehicle 120. The deflected signals 136, are Doppler shifted with respect to the impinging signals 134 and to the direct signals 132, due to the motion of vehicles 120 and 1 10. The system on vehicle 1 10 use the signals 136 received by antenna 1 16, and other information or signals it has, for deducing the distance, velocity and direction of vehicle 120 with respect to vehicle 1 10. A relative position, speed and direction vectors may be now computed to determine if the two vehicles 1 10 and 120 may collide. According to an embodiment an alert may be provided to the driver of the vehicle 1 10, or otherwise an action may be initiated, for example, causing the vehicle 1 10 to either accelerate or decelerate as the case may be. In yet another embodiment, the vehicle 1 10 may be further steered away from the potential collision point. In one embodiment, for the purpose of reducing false alerts, the system 200 may compute the required deceleration of the first vehicle 1 10 (using the velocities Vi and V2 and the position of the vehicles) and compare it to the typical deceleration rates of the specific driver. Only if the deceleration rate exceeds a specific threshold (learned from a short training phase for this specific driver) will the system 100 trigger an alert. One of ordinary skill in the art would readily realize that while a single satellite 130 is shown, use of a plurality of such GNSS satellites is possible without departing from the scope of the invention.

21] Reference is now made to Fig. 2 where an exemplary and non-limiting schematic block diagram of a system 200 for determination of potential collision paths according to an embodiment is shown. The system 200 is designed to be mounted in a vehicle, for example vehicle 1 10, as discussed hereinabove. The system 200 comprises a first antenna 1 14, the antenna adapted to receive signals from one or more GNSS satellites, and further adapted to be mounted on the vehicle in a general vertical orientation for the purpose of receiving signals directly from the one or more GNSS satellites within its sight. The first antenna 1 14 is connected to a first receiver 205 which is further connected to circuit 201 , and discussed in further detail herein below. A second antenna 1 16 is adapted to receive signals deflected from one or more moving objects at the vicinity of the vehicle, and further adapted to be mounted on the vehicle so as to receive horizontally deflected signals. In one embodiment the antenna 1 16 is a phased array antenna. The deflected signals are signals from the one or more GNSS satellites that are deflected from objects, for example, vehicle 120, being at the vicinity of the vehicle, for example, vehicle 1 10. The second antenna 1 16 is connected to a second receiver 215 which is further connected to circuit 201 , and discussed in further detail herein below. In an embodiment antenna 216 is a Left Handed Circularly Polarization (LHCP) antenna instead of the regular Right Handed Circularly Polarization (RHCP) antenna, used for example for antenna 1 14. This is done in order to minimize (e.g., by ^~ 20dB) direct line-of-sight reception from the satellite 130. The GNNS signal 134 is transmitted as RHCP but the first reflection from a metallic substance is mostly LHCP, thus, deferring it from the original signal and providing better signal-to-noise ratio at receiver 215.

[0022] The circuit 201 may have various embodiments, one of which is a processor capable of processing the inputs provided by the first receiver 205 and the second receiver 215. In one embodiment receiver 205 and receiver 215 share the same clock provided, for example, from circuit 201 . Furthermore, circuit 201 may provide information gathered from receiver 205 to receiver 215. Circuit 201 may process the signals from the first receiver 205, to obtain the position and velocity and direction of vehicle 1 10. Such determination of attitude may be done using frequency shift due to a Doppler effect as well as pseudo-range of the first vehicle 1 10. Circuit 201 may process signals from second receiver 215, with or without relation to signals from first receiver 205, to obtain the distance and velocity components of vehicle 120 with respect to vehicle 1 10. Such determination may be done by determining the pseudo-range and the Doppler shift of the signals received from receiver 215, preferably with respect to processed or non-processed signals from receiver 205. In another embodiment additional or alternative circuits may be used.

[0023] For example, and without limitation, circuit 201 is comprised of a velocity determination unit (VDU) 210 that may receive the signals received from the first receiver 205 and determine at least the velocity of the vehicle. The output 212 of VDU 210 may be fed as an input to a relative velocity determination unit (RVDU) 220, that determines at least the relative velocities between, for example, the vehicle on which the system 200 is mounted on, and an object from which signals are reflected from, for example, vehicle 120. This may be done, for example, by using multiple measurements respective of the received signals using the frequency shift Doppler effect respective of the signals. The RVDU 220 therefore receives the velocity of from VDU 210 and the information respective of the deflected signals from the second receiver 215 Determination of the relative speed between two objects is not sufficient to determine if there are on a collision path and therefore it is also important to determine their direction, that is having a vector of speed and direction for the vehicle on which the system 200 is mounted on, for example vehicle 1 10, and a vector of speed and direction for the second vehicle, for example, vehicle 120. These determinations may be performed by circuit 201 as a whole or in the combination of VDU 210 and RVDU 220. RVDU 220 may be further adapted to provide a notification, an alert, or otherwise commands to take action on signal 222. An alert or notification may be a sound notification or visual notification provided to the driver of the vehicle, while a command to take action may break the vehicle, accelerate or decelerate the vehicle as may be deemed fit by circuit 201 in order to avoid the collision.

[0024] In one embodiment of the system 200 there is further provided a connection to a local or remote database of maps where at least one map provides for the roads in the area wherein the vehicle, for example vehicle 1 10, operates in. The information provided from the map is used by the circuit 201 to more accurately determine the potential of collision between vehicles. For example, in the case shown in Fig. 1 B the road 101 may in fact be a bridge that goes over rod 102 and therefore even though it may seem that a collision may occur in a two dimensional view still a collision will not occur as there is an elevation separation between the two roads. Such information may assist in avoiding false alarms or actions. In another embodiment of the system 200, the relative altitude of vehicle 1 10 with respect of vehicle 120 is determined to further determine the existence of a potential future point of collision.

[0025] In yet another embodiment of the system 200, one or more sensors 240 may provide information to the circuit 201 . The use of sensor such as, but not limited to, velocity sensors, inertial sensors, digital compass, and/or other types of sensors, may provide additional information that can augment the information from the direct signals received from the satellite to further determine the location, orientation and speed of the vehicle on which system 200 is mounted on. It further may determine when to trigger an alarm or take other action , thereby, reducing false alarms.

[0026] Fig. 3 is an exemplary and non-limiting flowchart 300 of the operation of the system for determination of potential collision paths according to an embodiment. In S310 determination is to be made of the attitude, for example speed and direction, of the vehicle, using a first antenna, for example antenna 1 14, adapted to receive signal in essential a vertical direction from the vehicle form one or more GNSS satellites. In S320 a relative speed between the vehicle and another object, preferably a moving object, is determined respective of deflected signals from the one or more GNSS satellites, the deflected signals coming from the other object, where reception is performed by use of a second antenna, for example antenna 1 16, mounted on the vehicle in essentially a vertical orientation. In S330 it is determined if the vehicle and the other object are in potential collision path. In one embodiment such determination is further made with respect of information of roads as provided, for example, on a digitized map. In S340 an alert and/or an action are generated in order to avoid a collision upon determination that there is a potential of a collision between the vehicle and the other object. Determination of the need for an alarm or action may be further the result of an input of one or more of the sensors 240. In S350 it is checked if the method should continue its operation and if so executions continues with S310; otherwise, execution ceases.

[0027] Reference is now made to Fig. 4 that depicts an exemplary and non-limiting schematic diagram 400 for the purpose of calculation of a potential collision between two vehicles without the use of a digital map, and to Fig. 5 that depicts an exemplary and non-limiting schematic diagram 500 for the purpose of calculation of a potential collision between two vehicles with the use of a digital map 550. In Fig. 4, the lack of a digital map results in no information for the system 200 to determine potential future direction of the vehicles 1 10 and 120 respective of actual road conditions, and therefore the assumption is that the vehicles will continue in the direction and speed in which they currently are, for the purpose of the calculation of potential collision. As can be seen in Fig. 5, that has the same relative layout of vehicles 1 10 and 120, however, the use of the digital map 550 shows that a bend in the road on which vehicle 120 is traveling upon may bring the vehicles 1 10 and 120 to the collision point 103 at the same time. Hence, one of ordinary skill in the art would readily appreciate that the use of a digital map 550 input from a maps database 230, while a more complex system, provide a more accurate result of potential collisions between vehicles.

[0028] Fig. 6 shows an exemplary and non-limiting flowchart 600 for the calculation of a potential collision between two vehicles 1 10 and 120 without the use of a digital map. This flowchart 600 is best understood with respect of Fig. 4. There are several assumptions to be considered with respect of flowchart 600 as detailed herein: satellite 130 position and velocity are known (Xs,Vs) either by a reference GNSS receiver (205 and/or parts of circuit 201 ) or by other means (e.g., web); Vehicle 1 1 0 position and velocity is known (XA,VA) by a reference GNSS receiver (205 and/or parts of circuit 201 ) and VDU (210), with/without inertial or velocity sensors (240); Directional antenna (1 14) steering angle β is known; Pseudo range (code/phase or both) of direct-line reception from satellite 130 to vehicle 1 10 is known by a reference GNSS receiver (205 and/or parts of circuit 201 ) and VDU (21 0) ; The total Doppler shift of a signal transmitted by satellite 130, reflected by vehicle 120 and received by antenna 1 16 of vehicle 1 10 is: VSR-VRS+VRA-VAR; Digital map information is not available; Doppler shift between satellite 130 and vehicle 1 10 depends on both VRA and VRS, therefore at least two satellites are required for a complete solution (no ambiguity); and, Receivers 205 and 215 share the same clock which is synchronized to the GNSS clock by receiver 205. According to an embodiment an objective is to trigger an alert, alarm, or any other active measure if: t _CO iiision= dRA /(VRA- VAR)< shoid.

[0029] Solely for purpose of clarity and not by means of limitation, the operation of the GNSS is explained in a simplified manner. The signal 132 transmitted from the satellite 130 is modulated by a code and carries among other information, a time stamp. The code modulation and the time stamp provide information on the time at which the signal 132 has been transmitted. The signal 132 received by a receiver, e.g., receiver 205, is delayed by the travel time from the satellite 1 30 to the receiver 205, and furthermore is Doppler shifted due the relative velocity between the satellite 130 and the receiver 205 mounted on vehicle 1 10. Parts of circuit 201 create a "replica" of the coded signal and adjusts the replica code frequency and its time delay, until the best correlation between the received signal and the replicated code is obtained. From the time delay the distance between the satellite and the receiver is calculated (referred to as pseudo range ASA of the direct-signal 1 32) and from the Doppler shift vehicle 1 10 velocity may be calculated.

[0030] Circuit 201 may also perform similar process on the direct signal 132 to obtain the pseudo-range ASA and the Doppler shift of the direct signal, and on the reflected signal 136 to obtain correlation map as a function of pseudo range and Doppler shift of the reflected signal 136, from which a pseudo-ranges ASA + x of the reflected signal is derived, whereas x must be positive (reflected signal goes over larger distance). Knowing the position XA of vehicle 1 10, the antenna 1 16 steering direction angle (β), and the value of x, the position XR of the reflector, e.g., vehicle 120, can be estimated by applying simple trigonometric relationships on a triangle with apexes at the satellite 130, the vehicle 1 10 and the reflecting object e.g. vehicle 120, the said triangle having at least one known angle, one known satellite 130 - vehicle 1 10 edge and known sum of the other two edges derived from x). Given XA and XR the line CIRA is known.

[0031 ] Hereinafter, the principles of exemplary and non-limiting flowchart 600 are described. A correlation map (pseudo-range versus Doppler shift) of the reflected signal (136) and the pseudo-range of the direct-signal (132) are calculated. Given a direct signal pseudo-range ASA a search for a Doppler shifted signal having pseudo-ranges ASA + x in the reflected signal correlation map, whereas, x must be positive (reflected signal goes over larger distance) is performed. For each pseudo-range ASA + x a Doppler-shift correlation signal is derived from which the measured Doppler shift for pseudo-range x is extracted. In addition the expected theoretical Doppler shift of the vehicle (120) moving in velocity VRA - VAR > Vthreshoid towards (1 10) can be computed, given the velocities and positions of vehicle 1 10, vehicle 120, and satellite 130 on the line CIRA. Obviously, the Doppler shift depends on both VRA and VRS that are not necessarily aligned, therefore a single equation may not be sufficient. Moreover, VRS is different for each satellite 130. To solve the ambiguity, it is necessary to solve these equations for at least two satellites 130 and both must agree on the same pseudo-range x and VRA. Having more than two satellites 130 is preferred as this shall improve accuracy and reduce false-alarms by triangulating the estimated measurements. The classical dilution-of-precision (DOP) metric is relevant in this case as well. If both the theoretical and measured Doppler shifts agree, a positive detection has been achieved and the pseudo-range X=CIRA and the velocity VRA of the reflector are therefore determined.

[0032] The same process continues for different steering angles (β) . If CIRA / (VRA- VAR) < threshold then a collision warning signal may be triggered. In one embodiment an alarm will be sound, while in another embodiment the vehicle 1 10 may be ordered to stop, accelerate or decelerate in order to avoid the collision. The pseudo range estimation can be improved by using the P(Y) code (the military code used by GNSS), without knowing the cypher, as it only requires to correlate the direct-signal with the reflected signal to get the correlation map. Knowing the exact Doppler shift, where each satellite 130 transmits both C/A and P(Y) codes, it is possible to stretch or squeeze the frequency of the direct-signal 132 and cross-correlate it with the reflected signal 136 to get an improved pseudo range estimation. The private case of head-on collision, i.e., two vehicles in the same lane or a vehicle deviating from an opposite lane, requires only a single satellite 130, assuming that both vehicle 1 10 and vehicle 120 do not change their direction, approximating the road as a straight line in the direction of VA.

[0033] Reference continues with Fig. 6 where an exemplary and non-limiting flowchart 600 for the calculation of a potential collision between two vehicles 1 10 and 1 20 without the use of a digital map is shown. In S610 a reference pseudo-range ASA from for satellites 130 i.e., satellites 1 ..N, where N is an integer equal to or great than 1 is determined. Therefrom a correlation map for pseudo-ranges longer than ASA is determined as well as Xs,Vs for satellites 130 1 ..N. In S620 the Doppler shift in pseudo-range ASA + x from the correlation map for each satellite 130 is determined. In S630 Calculate the reflector position XR for excessive pseudo-range x in steering angle β from XA for each satellite is calculated. In S640 the theoretical Doppler shift for a reflector, e.g., vehicle 120, positioned at XR having a direct-line velocity VRA such that VRA- VAR>V _t hreshoid for each satellite 130. In S650 it is estimated whether the Doppler is with the range of theoretical Doppler for all satellites 130 and if so execution continues with S670; otherwise, execution continues with S660. In S660 x and β values are modified and execution continues with S620. In S670 it is determined if CIRA / (VRA- VAR) is smaller than threshold and if so execution terminates; otherwise execution continues with S680. In S680 a collision warning, signal or action takes place in a distance CIRA=X & steering at an angle β. In one embodiment such determination in S680 may further involve the use of inputs from one or more sensors 240.

[0034] Fig. 7 depicts an exemplary and non-limiting flowchart 700 for the calculation of a potential collision between two vehicles with the use of a digital map 550. There are several assumptions to be considered with respect of flowchart 700 as detailed herein: satellite's 130 position and velocity are known (Xs,Vs) either by a reference GNSS receiver (205) or by other means (e.g., web); Antenna 1 14 position and velocity are known (XA,VA) by a reference GNSS receiver (205) with/without inertial or velocity sensors; Directional antenna 1 16 steering angle β is known; Pseudo range (code/phase or both) of direct-line reception from satellite 130 to vehicle 1 10 is known by a reference GNSS receiver (205); The total Doppler shift of a signal 132 transmitted by satellite 130, reflected by vehicle 120 and received by receiver 215 is: VSR-VRS+VRA-VAR; Digital map 550 information is available (roads and crossroads); A signal from at least a single satellite 130 is received by receiver 205; Receiver 205 and receiver 215 share the same clock which is synchronized to the GNSS clock by receiver 205. According to one embodiment an alert, or another active measure, is triggered if tcollision = |CIAC/VA " CIRC/VR| < threshold-

Hereinafter, the principles of exemplary and non-limiting flowchart 700 are described.

[0035] Knowing the position of vehicle 1 10 XA and the antenna 1 16 steering direction angle (β) , the position XR of the reflector, e.g., vehicle 120, can be estimated using a digital map 550 by intersecting the steering direction with the nearby road. Alternatively, one may use only the measured distance and a digital map 550, and find the intersection of a circle having a radius equal to the distance centered at the vehicle 1 10 with the nearby road. All those methods may ignore the Doppler effect information, and hence, be susceptible to detection of irrelevant objects, but may also consider only reflected signals having relevant Doppler shift.

[0036] It is therefore proposed to use the Doppler shift in order to filter out relevant reflections out of the multiple reflections expected to be received and simultaneously measure the reflector position and velocity (VR and XR). Given a direct signal 132 pseudo-range ASA a Doppler shifted signal having pseudo-ranges ASA + X in the reflected signal correlation map is searched for, where x must be positive, as the reflected signal 136 travels a larger distance. For each pseudo-range ASA + X a Doppler-shift correlation signal is determined from which there is extracted the measured Doppler shift for pseudo-range x. However, one can also compute the expected theoretical Doppler shift of a reflector (e.g., vehicle 120) moving in velocity VR where | VR |>V _t hreshoid towards vehicle 1 10 given the velocities and positions of vehicle 1 10, vehicle 120, and satellite 130 intersected with a digital map 550 to provide XR. If both agree (i.e., the theoretical and measured Doppler shifts) then both VR and XR of the reflector are known. The same process continues for different steering angles (β). The algorithm requires detection of at least a single satellite 130, however, use of multiple satellites 130 can improve the velocity and pseudo-range detection by triangulating the estimated measurements, hence, improving the DOP measure.

[0037] The advantage of using the digital map 550 provides prior information about possible pseudo-ranges which narrows down the search space in the correlation map, hence, reducing false alarms; reduces the velocity of the reflector to a 1 D vector, hence, requires a minimum of a single satellite 130; and, it enables estimation of time-to- collision (tcoiiision) . The pseudo range estimation can be further improved by using the P(Y) code (military code) without knowing the cypher as explained in more detail hereinabove with respect of Fig. 6, and hence not repeated here.

[0038] Assuming that most of the vehicles are either coated with metallic color or contain metal, it is expected that the reflected signal 136 will change the polarization of the satellite signal 134, hence, according to an embodiment a Left Handed Circularly Polarized (LHCP) antenna is used in order to amplify the signal from the reflector over the signal from other non-metallic objects. For further improvement of the spatial resolution of the system use is made of an accurate differential positioning of the vehicle 1 10 XA (using inertial sensors) and the steering angle β as well as the movement of the antenna, in order to create a Synthetic Aperture Radar (SAR) out of the received signal. Moreover, an embodiment of system 200 having both RHCP and LHCP antennas in order to create a polarization map of the objects detected, hence, gaining more information about the object composition may also be created. [0039] Reference continues with Fig. 7 where an exemplary and non-limiting flowchart 700 for the calculation of a potential collision between two vehicles 1 1 0 and 1 20 with the use of a digital map 550 is shown. In S710 a reference pseudo-range ASA, a correlation map for pseudo-ranges longer than ASA, and XS,VS,XA,VA, d _A c,dRc,B are determined. In S720 the Doppler shift in pseudo-range ASA + x from the correlation map is estimated. In S730 the reflector position XR for excessive pseudo-range x in steering angle β from XA is calculated. In S740 the theoretical Doppler shift for a reflector positioned at XR having a velocity VR such that | VR |>V _t hreshoid is calculated. In S750 it is checked whether the estimated Doppler is within the range of theoretical Doppler and if so execution continues with S770; otherwise, execution continues with S760. In S760 x, β are modified and execution continues with S720. In S770 it is determined whether |CIAC/VA - CIRC/VR| < tthreshoid and if so execution continues with S780; otherwise, execution terminates. In S780 a collision warning, or another passive or active action as discussed herein, is triggered or generated after which execution terminates.

[0040] The various embodiments disclosed herein can be implemented as hardware, firmware, software, or any permissible combination thereof. Moreover, the software is preferably implemented as an application program tangibly embodied on a program storage unit or computer readable medium consisting of parts, or of certain devices and/or a combination of devices. The application program may be uploaded to, and executed by, a machine comprising any suitable architecture. Preferably, the machine is implemented on a computer platform having hardware such as one or more central processing units ("CPUs"), a memory, and input/output interfaces. The computer platform may also include an operating system and microinstruction code. The various processes and functions described herein may be either part of the microinstruction code or part of the application program, or any combination thereof, which may be executed by a CPU, whether or not such a computer or processor is explicitly shown. In addition, various other peripheral units may be connected to the computer platform such as an additional data storage unit and a printing unit. Furthermore, a non-transitory computer readable medium is any computer readable medium except for a transitory propagating signal. 41] All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the principles of the disclosed embodiment and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the disclosed embodiments, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.