sdss_tiling_geometry.fits

This file is located at:

$VAGC_REDUX/sdss/sdss_tiling_geometry.fits

It describes the SDSS tiling geometry in terms of spherical polygons. This file can be read in using the 

read_fits_polygons

tool in idlutils.

The columns are:

  1. XCAPS[3,N]: directions for each cap (as specified in the mangle documentation)
  2. CMCAPS[N]: size of each cap (as specified in the mangle documentation)
  3. NCAPS: number of caps
  4. WEIGHT: weight assigned to each cap (ignore this)
  5. STR: area of each cap in steradians
  6. USE_CAPS: bitmask designating which caps to use
  7. SECTOR: index of sector to which this polygon belongs
  8. FIRSTBOUNDARY: first "boundary" which covers this area

Each "sector" is defined as a region which had the opportunity to be observed by a unique set of tiles. It is the natural unit on which to define the completeness. A sector may consist of one or more polygons. The parameters for each sector are in the file:

$VAGC_REDUX/sdss/sdss_sectorList.par

which is a Yanny parameter file with the columns:

  1. index: sector number
  2. tileId[20]: array with tiles which could observe this sector (0 indicates non-tile)
  3. nTiles: number of tiles in tileId array
  4. area: obsolete!
  5. nTargets: obsolete!
  6. nRandom: obsolete!

The parameters for the tiles are in the file:

$VAGC_REDUX/sdss/tileFull.par

which is a Yanny parameter file with the columns:

  1. tileid: identifier of tile
  2. racen: center of tile in right ascension, J2000 (deg)
  3. deccen: center of tile in declination, J2000 (deg)
  4. ntargets: number of tiled targets in tile
  5. chunk: tiling region ("chunk") which this tile belongs to

The boundaries and masks (which are explained more fully at the DR1 web site) are in the files

$VAGC_REDUX/sdss/tilingBoundary.par
$VAGC_REDUX/sdss/tilingMask.par

The tiling geometry files are a translation of these files into spherical polygons, so it is not necessary to understand the format of these files, except that one may want to translate FIRSTBOUNDARY into a target version by using the targetVersion column of the tilingBoundary.par file.

An ASCII version of the tiling_geometry file is at: 

$VAGC_REDUX/sdss/ascii/sdss_tiling_geometry.ply
$VAGC_REDUX/sdss/ascii/sdss_tiling_geometry_info.dat

The first file is the mangle-style description of the polygons. The second file stores the other pertinent information in the columns described above, in the format:

[sector] [firstboundary] [str]

NYU Value-Added Galaxy Catalog

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