Abstract: A differential odometer includes a left wheel sensor (503) coupled to a left wheel (103), and a right wheel sensor (513) coupled to a right wheel (105). The left wheel sensor (503) provides a left wheel pulse count (505) as the left wheel (103) rotates. A left wheel distance traversed is determined by a product of the left wheel pulse count and a left distance per pulse coefficient. The right wheel sensor (513) provides a right wheel pulse count (515) as the right wheel rotates. A right wheel distance traversed is determined by a product of the right wheel pulse count and a right distance per pulse coefficient. A vehicle heading (601'), and vehicle distance traversed (1201), are determined using the left wheel distance traversed and the right wheel distance traversed. A correction value (901, 1001) is provided corresponding to a measured relationship between the left wheel pulse count and the right wheel pulse count.

Abstract: An electronic compass (10) having at least two sense windings (11, 12) is mounted in a vehicle. The outputs (x(h), y(h)) of the windings are measured for a number of compass directions (headings). From this data an error difference angle (.phi.), from a nominal angle, which actually exists between the output windings is calculated. Preferably a look-up table (21, 39) is created relating actual compass heading (h) to measured sense winding outputs by utilizing the calculated error difference angle (.phi.). This table is then utilized for calculating actual compass heading based on actual measured sense winding outputs. The calculated error angle (.phi.) can also be used to calibrate the compass without creating a look-up table. The calibrated compass compensates for misalignment of the sense windings and provides a more accurate electronic compass without requiring creating a calibration table by orienting the compass in a very large number of exactly known directions.