Spherical Toolkit

This site is dedicated to light-weight software solutions that enable precise geometry operations on the surface of the sphere and efficient searches. Our toolkit consists of two key components that build on top of each other to achieve high precision and great performance. In addition to these libraries you will also find an extension layer for SQL Server that exposes most of the core functionality to be used in queries. In a recent paper we summarize the math behind it all, and provide details on the key features. Here you can also find a complete list of all our relevant papers. Get started now with some examples in C# and SQL.

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.

Please also make sure that you check out the Footprint Service, where you can experience some of these functionalities first hand without any programming. Search, create and visualize footprints in a just few clicks.