Travel-lane estimation system

A travel lane estimation system comprising:

• a GNSS receiver configured to receive a coordinate of a vehicle through a Global-Navigation-Satellite-System (GNSS);
• and
• circuitry configured to
• calculate a vehicle speed from a travel distance of the vehicle;
• measure an angular velocity from an amount of change in vehicle's orientation;
• calculate a reference coordinate of the vehicle and a reference orientation of the vehicle from the coordinate, and calculate time series data of positioning coordinates of the vehicle and positioning orientations of the vehicle from the reference coordinate, the reference orientation, the vehicle speed, and the angular velocity;
• store map information including information about node coordinates forming a road link, a road width, the number of lanes, and a travelable direction;
• calculate a division line of a lane from the map information;
• and
• calculate, as a calculated correction amount, an error pattern having a posterior probability that is the highest among a plurality of error patterns, correct the time series data using the calculated correction amount, and compare the time series as corrected with the division line, to estimate a travel lane of the vehicle, the posterior probability being calculated with a product of a prior occurrence probability of the time series data by the plurality of error patterns and a likelihood which is calculated, under a condition that the error pattern has occurred, on the basis of a relative positional relationship between the time series data after correction and the division line.