A trip meter, such as a taximeter or a mileage meter for a commercial vehicle, such as a truck, are combined with an integral GPS receiver/computer which provides GPS position and time information. Odometer input pulses to the trip meter are accurately calibrated by using GPS position, velocity, and time information to generate corrected odometer pulses which are provided to the odometer input terminal of the trip meter. The GPS system is integrated into the trip meter for calibrating and cross checking of the input odometer pulses to provide reliable, consistent distance measurements by the trip meter. GPS position, velocity, and time information produce incontrovertibly accurate corrected, odometer input pulses and GPS time signals for the trip meter to precisely compute elapsed time and distance traveled. A backup dead-reckoning subsystem operates when the GPS receiver has service outages. The GPS receiver/computer system provides trip information such as information about when and where the commercial vehicle enters and leaves a predetermined zone, information establishing proof of a path followed by the commercial vehicle, information about operation within speed limits, and information verifying operation within a certain geographic area. A data recorder records the trip information.