A GPS L1 amplitude scintillation test pattern based on measured GPS signal amplitudes is proposed as a first step toward developing a standard. The 300 s test pattern is created from a GPS signal experiencing moderate amplitude scintillations (0.3 < S4 < 0.6) as measured at Cachoeira Paulista, Brazil, during January 2001. By scaling the signal amplitudes to larger S4 values, the effect of severe scintillations on GPS receiver operation is investigated and is shown to produce serious loss of signal tracking and, in some cases, failure to navigate. The test pattern is publicly available for use in evaluating GPS receivers by acknowledging the source. Future work will focus on including phase scintillations to make a complete standard.