The Spherical Library provides an efficient
and accurate mathematical
representation of shapes on the celestial sphere, such as sky coverage and footprints.
Shapes of arbitrary
complexity and size can be dynamically created from simple building blocks,
whose exact area is also analytically computed. This methodology is also perfectly
suited for censoring problematic parts of datasets, e.g., bad seeing, satelite trails
or diffraction spikes of bright stars.
The Hierarchical Triangular Mesh or HTM for short, builds on
our spherical geometry routines to speed up spatial searches. These utilize approximate
shapes unions of small spherical triangles or trixels and the built-in indexing mechanism
of the database engines. Both packages come complete with advanced wrappers
that extend SQL Server's capabilities. If you
ever queried the SDSS, GALEX, HLA or the UKIDSS archives, chances are that
you have used these SQL routines before.