VizieR, HiPS, and MOC

VizieR provides access to the most complete library of published astronomical catalogues and data table available on-line, organized in a self-documented database.

HiPS is the hierarchical tiling mechanism, which allows one to access, visualize, and browse seamlessly, image, catalogue, and cube data.

MOC, the Multi-Order Coverage map method, allows to specify arbitrary sky regions, with very fast comparisons between them. It is based on the HEALPix sky tessellation algorithm.