Each tiling region is a union of rectangles on the sky in great circle or survey coordinates. There is one known bug in DR4 and DR5 in that tileRun 60, along the far end of stripe 82, has incorrect boundaries in the CAS database. The correct values for tileRun 60 are: (lambdamu_0, lambdamu_1, etanu_0, etanu_1, lambdaLimit_0,lambdaLimit_1) = (56.5088888889,58.45,-1.2586466,1.2586466,-9999,-9999) This bug will be corrected in DR6, it only slightly affects calculations of total area coverage for the imaging and spectroscopy in DR5. The amount of difference bay be ignored for most purposes.