Systems and methods for monitoring the accuracy of a global positioning system (GPS) receiver in a marine vessel utilize a GPS receiver receiving a plurality of satellite signals, calculating a global position of the GPS receiver based on the plurality of signals, and determining a signal to noise ratio (SNR) of each signal in the plurality of signals; and a control circuit having a computer readable medium having executable code, and being connected to the GPS receiver by a communication link. The control circuit calculates an average SNR of the plurality of signals and compares the average SNR to a threshold SNR. In one example the threshold SNR varies depending upon a number of satellites sending the plurality of signals and a speed at which the marine vessel is traveling.