The u′g′r′i′z′ standard-star system

We present the 158 standard stars that de ne the u' g' r' i' z' photometric system. These stars form the basis for the photometric calibration of the Sloan Digital Sky Survey. The de ning instrument system and filters, the observing process, the reduction techniques, and the software used to create the stellar network are all described. We briefly discuss the history of the star selection process, the derivation of a set of transformation equations for the UBVRCIC system, and plans for future work.