A method of indicating whether a GPS signal received by a vehicle is accurate includes obtaining the GPS signal and calculating position information of the vehicle based on the GPS signal. The method further includes obtaining position information of another vehicle via a broadcast. The method further includes calculating a first distance information to the other vehicle based on the position information of the other vehicle and the position information of the vehicle. The method further includes obtaining a second distance information to the other vehicle via a collision avoidance system on the vehicle. The method further includes comparing the first distance information to the second distance information, and generating an indicator that the vehicle and the other vehicle may have received an inaccurate GPS signal when a result of the comparison is higher than a threshold.