Estimation of vehicle location
A method for estimating the position of a telematics-equipped vehicle during navigation includes: receiving a partial map corresponding to a route; receiving Global Positioning System (GPS) data corresponding to a current position of the vehicle; performing a closest street (CS) mapping based on the GPS data and the partial map so as to provide an estimation for a vehicle position on a street of the partial map; performing speed sum (SS) mapping based on the estimated vehicle position and speed readings corresponding to vehicle speed so as to provide an estimation of distance traveled with reference to a previous vehicle position; and presenting a map matched vehicle position to a user based on the CS mapping and the SS mapping.
1. A method for estimating the position of a telematics-equipped vehicle during navigation, the method comprising:
receiving, by a telematics unit, a partial map corresponding to a route, the partial map corresponding only to street segments to be traversed on the route;
determining, by the telematics unit, an initial position of the vehicle based on satellite positioning data;
calculating, by the telematics unit, a distance between the initial position of the vehicle and a point of a closest street on the partial map and calculating a closest street (CS) confidence value based on the distance;
comparing, by the telematics unit, the CS confidence value to a threshold CS confidence value and, in response to a result of the comparison, executing a map matching (MM) procedure, the MM procedure comprising:
calculating a distance traveled by the vehicle since the initial position of the vehicle based on speed readings acquired from vehicle sensors;
calculating a speed sum (SS) confidence value based on past speed quality values obtained from past satellite positioning data and past calculated CS confidence values; and
comparing a combination of the CS confidence value and the SS confidence value to a MM update threshold value and, in response to a result of the comparison, determining a map-matched position on the partial map corresponding to the initial position and the distance traveled by the vehicle since the initial position; and
causing, by the telematics unit, the map-matched position of the vehicle to be presented as an updated current position of the vehicle.
2. The method of claim 1 , wherein the CS confidence value is inversely proportional to the calculated distance between the initial position of the vehicle and a closest street on the partial map.
3. The method of claim 1 , further comprising:
comparing, at a later time, a later calculated CS confidence value to the threshold CS confidence value and, in response to a result of the comparison, starting a timer; and
determining that the vehicle is off-route or that positioning information is unreliable in response to determining that the timer reaches a predetermined amount of time without any calculated CS confidence values being above the threshold CS confidence value during the predetermined amount of time.
4. The method of claim 1 , further comprising:
performing turn detection (TD) and calculating a TD confidence value based on a comparison between a difference in vehicle headings and a difference in street headings.
5. The method of claim 4 , wherein performing TD further comprises at least one of:
comparing a difference between vehicle headings at two distinct times with a difference in street headings at two distinct positions, wherein the two distinct positions correspond to estimated vehicle positions at the two distinct times; and
comparing a difference between vehicle headings at two distinct distances from a reference point with a difference in street headings at the two distinct distances from the reference point.
6. The method of claim 4 , wherein the combination of the CS confidence value and the SS confidence value further includes the TD confidence value.
7. A telematics unit having a non-transitory, computer-readable medium with computer-executable instructions for estimating the position of a telematics-equipped vehicle during navigation stored thereon, the computer-executable instructions, when executed by a processor, causing the telematics unit to perform the steps of:
receiving a partial map corresponding to a route, the partial map corresponding only to street segments to be traversed on the route;
determining an initial position of the vehicle based on satellite positioning data;
calculating a distance between the initial position of the vehicle and a point of a closest street on the partial map and calculating a closest street (CS) confidence value based on the distance;
comparing the CS confidence value to a threshold CS confidence value and, in response to a result of the comparison, executing a map matching (MM) procedure, the MM procedure comprising:
calculating a distance traveled by the vehicle since the initial position of the vehicle based on speed readings acquired from vehicle sensors;
calculating a speed sum (SS) confidence value based on past speed quality values obtained from past satellite positioning data and past calculated CS confidence values; and
comparing a combination of the CS confidence value and the SS confidence value to a MM update threshold value and, in response to a result of the comparison, determining a map-matched position on the partial map corresponding to the initial position and the distance traveled by the vehicle since the initial position; and
causing the map-matched position of the vehicle to be presented as an updated current position of the vehicle.
8. The telematics unit of claim 7 , wherein the CS confidence value is inversely proportional to the calculated distance between the initial position of the vehicle and a closest street on the partial map.
9. The telematics unit of claim 7 , wherein the computer-executable instructions, when executed by the processor, further cause the telematics unit to perform the steps of:
comparing, at a later time, a later calculated CS confidence value to the threshold CS confidence value and, in response to a result of the comparison, starting a timer; and
determining that the vehicle is off-route or that positioning information is unreliable in response to determining that the timer reaches a predetermined amount of time without any calculated CS confidence values being above the threshold CS confidence value during the predetermined amount of time.
10. The telematics unit of claim 7 , wherein the computer-executable instructions, when executed by the processor, further cause the telematics unit to perform the steps of:
performing turn detection (TD) and calculating a TD confidence value based on a comparison between a difference in vehicle headings and a difference in street headings.
11. The telematics unit of claim 10 , wherein performing TD further comprises at least one of:
comparing a difference between vehicle headings at two distinct times with a difference in street headings at two distinct positions, wherein the two distinct positions correspond to estimated vehicle positions at the two distinct times; and
comparing a difference between vehicle headings at two distinct distances from a reference point with a difference in street headings at the two distinct distances from the reference point.
12. The telematics unit of claim 10 , wherein the combination of the CS confidence value and the SS confidence value further includes the TD confidence value.