# lsst.skymap¶

The skymap package provides tools for creating pixelizations of the sky to define tracts and patches for imaging data.

A sky map describes a pixelization of image data that covers most or all of the sky. The imaging data is arranged as a sequence of overlapping rectangular “tracts”. Each tract is, in essence, a single large exposure. However, tracts are typically too large to fit into memory, so tracts are subdivided into rectangular, possibly overlapping “patches”. The patch size is chosen to easily fit into memory.

## Contributing¶

lsst.skymap is developed at https://github.com/lsst/skymap. You can find Jira issues for this module under the skymap component.

## Python API reference¶

### lsst.skymap Package¶

#### Functions¶

 makeSkyPolygonFromBBox(bbox, wcs) Make an on-sky polygon from a bbox and a SkyWcs

#### Classes¶

 BaseSkyMap([config]) A collection of overlapping Tracts that map part or all of the sky. BaseSkyMapConfig DiscreteSkyMap(config[, version]) Discrete sky map pixelization. DodecaSkyMap([config]) Dodecahedron-based sky map pixelization. DodecaSkyMapConfig EquatSkyMap([config]) Equatorial sky map pixelization, e.g. EquatSkyMapConfig PatchInfo(index, innerBBox, outerBBox) Information about a patch within a tract of a sky map. TractInfo(id, patchInnerDimensions, …) Information about a tract in a SkyMap sky pixelization

### lsst.skymap.detail Package¶

#### Functions¶

 coordFromVec(vec[, defRA]) Convert an ICRS cartesian vector to an ICRS lsst.geom.SpherePoint

#### Classes¶

 Dodecahedron([withFacesOnPoles]) A dodecahedron with positions of faces and associated vertices. WcsFactory(pixelScale, projection[, …]) A factory for creating Wcs objects for the sky tiles.

### lsst.skymap.cachingSkyMap Module¶

#### Classes¶

 CachingSkyMap(numTracts[, config, version]) A SkyMap that generates its tracts on request and caches them.

### lsst.skymap.healpixSkyMap Module¶

#### Classes¶

 HealpixSkyMapConfig Configuration for the HealpixSkyMap HealpixSkyMap(config[, version]) HEALPix-based sky map pixelization.

### lsst.skymap.ringsSkyMap Module¶

#### Classes¶

 RingsSkyMapConfig Configuration for the RingsSkyMap RingsSkyMap(config[, version]) Rings sky map pixelization.