SDSS Data Management and Photometric Quality Assessment
  We summarize the Sloan Digital Sky Survey data acquisition and processing steps, and describe runQA, a pipeline designed for automated data quality assessment. In particular, we show how the position of the stellar locus in color-color diagrams can be used to estimate the accuracy of photometric zeropoint calibration to better than 0.01 mag in 0.03 deg2 patches. Using this method, we estimate that typical photometric zeropoint calibration errors for SDSS imaging data are not larger than ~0.01 mag in the g, r, and i bands, 0.02 mag in the z band, and 0.03 mag in the u band (root-mean-scatter for zeropoint offsets). 
Z. Ivezic, R.H. Lupton, D. Schlegel, B. Boroski, J. Adelman-McCarthy,   B. Yanny, S. Kent, C. Stoughton, D. Finkbeiner, N. P...