Method for updating in a wheeled vehicle steered by dead reckoning

In a wheeled vehicle steered by a method of dead reckoning, whereby said vehicle computes a position and attitude from rolled off distance measurements representing linear motion of said vehicle, a method for updating said vehicle position coordinates by detecting said vehicle position with respect to first and second linear markings which intersect each other on the surface supporting said vehicle comprising:

• optically scanning said surface with a linear detector positioned on said vehicle to determine positional points on said detector intersected by said linear markings;
• determining, at first and second positions of said vehicle, the intersection of each of said first and second linear markings with said linear detector, each of said intersections representing a lateral deviation of each of said linear markings with respect to said vehicle at said first and second positions;
• determining the difference in lateral deviation between each of said markings and said vehicle at each of said positions whereby first and second differences in lateral deviation A30, A31, for each of said positions are determined;
• measuring the rolled off distance S31 traversed by said vehicle between said first and second positions;
• and,
• determining the distance Y between one of said vehicle positions and the intersection of said first and second linear markings from said rolled off distance S31 and said differences in lateral deviation A30, A31, whereby said vehicle position with respect to said intersection of said linear markings is determined.