Relations between photometric uncertainties and magnitudes for sources in a partial region of “d003” (∼3′ × 3′ central region of tile “d003”). The gray dots represent all detected sources. The flagged spurious detections are marked with green dots. The blue curves show the exponential fittings for all the sources while the red curves mark the corresponding thresholds of photometric uncertainties that are used to flag the possible spurious detections.