The Commer has an original fitment electric and gas-powered gyro-inertial navigation system, it was made by Lucas in the Sixties.
The moving map display is fitted on the main instrument panel and the "works" is hidden in the rear of the van with the feed from the calor gas bottle. It is an electro-mechanical system with a stylus indicating the vehicle position over a motor-driven paper map roll. Position is derived from a doppler navigation system which calculates speed with heading data to drive motors moving the stylus from side to side for lateral position, and the paper roll itself for the track. You simply enter the coordinates for the starting point and set off. Like the useless mechanical fuel injection systems in the contemporary Triumph PIs, Lucas were plagued with it's terrible reliability. Also, the pilot light kept going out, and you have to get underneath with a long match to relight if the Pezo won't work. Poor reputation and high initial expense meant it never really caught on.
These days, I have to say once it's valves have warmed up, it's pretty accurate.
