This is just another of the variations that cause the inequalities within pigeon racing. There is nothing fair or precise within the hobby. Pinpoints on maps or GPS, the accuracy of both matter not a jot with regard to race distance, except that there is less scope for human error using GPS. Race distance accuracy is a fallacy in respect of the actual distance flown. Weather conditions and geography can cause the pigeons to fly further than the measured distance. Different parking position of the transporter from the measured point makes no difference because the different position is the same for all on the transporter, so the variation will also be the same for all. Multiple transporters liberating for the same race would make more of a difference. Be content that pigeon racing will never be fair, all we can hope for is to reduce the number of anomalies, accept the winning pigeon "on the day" and also start giving credit to the pigeons that overcome the geographical and weather obstacles placed before them within the same race. Some pigeons may never win a race, but may "score" in many races. These multiple performing pigeons can be better for your loft than a pigeon with a "one off" top result, without discrediting the pigeon that has the top result.