This is the web site for the Spherical-Cube Quad-Tree Unique ID Library (LibSQUID). The purpose of this library is to provide a set of tools for indexing/dividing a set of data on a spherical coordinate system (i.e. geospatial metadata) using a quad-tree indexing scheme applied to a quad-cube cartographic projection.
The LibSQUID library consists of a set of functions written in C which allow a user to index a sphere at a specified resolution using a quad-tree indexing scheme. The indexes themselves are called SQUIDs, short for Spherical-cube Quad-tree Unique ID. Each SQUID index directly corresponds to a point on the sphere given by a (longitude,latitude) coordinate. In addition, the SQUID defines a region on the sphere, which I call a “tile”, that has well defined boundaries. Currently, the LibSQUID system supports four quad-cube cartographic projections; Tangental, COBE, Quadrilateralized, and HEALPix.
The LibSQUID library can be used to efficiently index, store, and retrieve any data taken on a spherical coordinate system. Although our primary application is the efficient storage and recall of wide-field astronomical FITS images, this is by no means the only potential use of the library.