Accurate localization of a remote vehicle
1) Calibrated Odometer method with GPS sync

Car Speedometers and odometers are often inaccurate due to choices with oversized tires.  But with on-board computers and some calibration routine , it is theoretically possible to get high accuracy. The integration of this error must be specified by your system specs.  

You must start with an error budget and allocate in parts per million xxx ppm for each source of error: mfg tolerance , tire, wear , cornering slip, loose surface grip, brake skids, elevation changes in Z axis.

Then determine when resync is needed with GPS.  Keeping a rolling history of cumulative Position Error , forever, for create an algorithm for forward error correction from each of these above error budget sources. Then create Forward Predictor Correction factors for each cause to reduce the need to resync with GPS.  

It may depend on your accuracy tolerance, and integration time response specs to determine the optimal trade off between quadrature dual wheel incremental encoders and GPS .  Compute the sensitivity to errors if you wish to find the opportunities for improvement. 

Always start with good specs with assumptions then verify, improve and repeat until ok.

2) Alternatively, if you rely on a mobile with MEMs accelerometer, Gyro and GPS, and just use an SDK to interface to the API , then it becomes a selection process and software needs starting again with a MODIFIED spec.