All sorts of positioning system exist and there is a growing demand nowadays in order to provide users with additional data in many activities. Horce racing is no exception and the PMU (Paris Mutuel Urbain) is in charge of driving the project concerning the deployment of a tracking system. PMU is Europe's largest betting operator. It is an Economic Interest Grouping (EIG), whose mission is to finance the French horce racing industry. The specifications of the tracking system to be implemented are quite tough : an accuracy of positioning of 25 cm for more than 98 % of the time during races for all the horses. A call for proposals has been issued and a few competitors have been hired in order to demonstrate the real performances on their system in a so-called "pilot" phase. The problem we now have is how to evaluate the real accuracy of the system in real conditions,i.e., during "simulated races" Additional aspects are also of uppermost importance, such as the latency and the way data are displayed, but the present paper will only focus on the evaluation methodology used for the positioning accuracy assessment. An incremental validation approach was set up in order to allow the competitors to gradually improve their solutions, from the "easiest" tests (with cars) to the "most difficult" ones on horses during simutated races. Note that all competitors proposed a GNSS (Global Navigation Satellite System)-based solution using an RTK (Real-Time Kinematic) approach