If you add two Compatts to a vehicle, these will both be used to track the vehicle as long as they have appropriate references. If you wish to track the two independently (i.e. no knowledge of the fact they are mounted on the same structure and constrained by a known distance),we would suggest creating two vehicles (structures) and add a Compatt to each. Then you can track both simultaneously within the same array. Tracking two independent vehicles is mathematically different to tracking one with two Compatts mounted so you may see variation in the position differences.