Hierarchical subdivision of spherical triangles
represented as a quadtree
In SDSS the tree is 5 levels deep - 8192 triangles,
In 2MASS the tree goes much deeper in the Galactic plane
One shoe fits allÖ
This indexing is now adopted by SDSS, 2MASS, GSC2, POSS2, FIRST and is considered by CDS, PLANCK and GAIA
New standard spatial index for astronomy!
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