Private, auditable vehicle positioning system and on-board unit for same
This invention relates to a system and method to generate a private, auditable, evidentiary quality record of the location-history of an asset or person. This invention addresses ten critical improvements over existing systems that are proposed or used for metering for payment services for tolling roads, parking or pay-as-you-drive insurance, namely, cost-effective location accuracy in harsh signal environments, evidentiary assurance of location estimation, handling of dynamic and stationary positioning in a single device, high-ratio compression for a set of stationary positions in urban canyon, high-ratio compression for a dynamic tracklog in urban canyon, high-ratio compression for a set of asset motion behaviors, a method of remote device health check, including anti-tampering, removal of residual price assignment errors, anonymous use without on-board maps, and a method of deconsolidating payments to multiple payees with multiple payment regimes. This system can be applied to road-pricing, congestion-pricing, metered-by-the-minute parking and pay-as-you-drive insurance, incorporating privacy management, and legal admissibility of the evidentiary record. This same device can also be applied to vehicular fleets, military ordinance, or other location audits for assets whether motorized or not, as might be needed in evidence of contract fulfillment or other forms of non-realtime geofencing audits.
1. A computer implemented method of tracking the position of an object, the method comprising:
receiving positioning data with respect to the object's position in timed intervals;
calculating, by operation of one or more processors, a position estimate and associated error bound for each timed interval based upon the received positioning data;
fitting each calculated position estimate and associated error bound to a grid of cells, wherein each cell is assigned a price in a pricing map;
calculating statistical weight of positional certainty of each position measurement by distributing geometric weight of each associated error bound over the cells which said error bound overlaps; and
calculating a maximum-likelihood path of travel based upon the weighted position measurements, wherein the maximum-likelihood path of travel is stored as a data set in a quad tree including a grid cell designator, weighted time in cell, weighted distance travelled in cell, time of earliest position estimate in cell, and time of latest position estimate in cell.
2. The method according to claim 1 , further comprising computing, for each cell in the quad tree, a charge based on the weighted distance travelled within that cell, preferably as set by a schedule price given by the midpoint time of samples within that cell, being the time of latest position estimate in cell minus the time of earliest position estimate in cell, divided by two.
3. The method according to claim 2 , wherein if the maximum-likelihood path of travel hovers on the edge of two cells having different pricing assigning to the cell with the smaller charge all of the duration and distance of those two cells.
4. The method according to claim 1 , wherein the pricing map is flat in a region of relatively wide error bounds, each cell in that region having the same price as its neighbouring cells.