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10.5.1 Tilings

Pixel tiling functions for the celestial sphere.

The k parameter for the HEALPix functions is the HEALPix order, which can be in the range 0<=k<=29. This is the logarithm to base 2 of the HEALPix NSIDE parameter. At order k, there are 12*4^k pixels on the sphere.

htmIndex( level, lon, lat )
Gives the HTM (Hierachical Triangular Mesh) pixel index for a given sky position.
healpixNestIndex( k, lon, lat )
Gives the pixel index for a given sky position in the HEALPix NEST scheme.
healpixRingIndex( k, lon, lat )
Gives the pixel index for a given sky position in the HEALPix RING scheme.
healpixNestLon( k, index )
Returns the longitude of the approximate center of the tile with a given index in the HEALPix NEST scheme.
healpixNestLat( k, index )
Returns the latitude of the approximate center of the tile with a given index in the HEALPix NEST scheme.
healpixRingLon( k, index )
Returns the longitude of the approximate center of the tile with a given index in the HEALPix RING scheme.
healpixRingLat( k, index )
Returns the latitude of the approximate center of the tile with a given index in the HEALPix NEST scheme.
healpixNestToRing( k, nestIndex )
Converts a healpix ring index from the NEST to the RING scheme at a given order.
healpixRingToNest( k, ringIndex )
Converts a healpix ring index from the RING to the NEST scheme at a given order.
healpixK( pixelsize )
Gives the HEALPix resolution parameter suitable for a given pixel size. This k value is the logarithm to base 2 of the Nside parameter.
healpixResolution( k )
Gives the approximate resolution in degrees for a given HEALPix resolution parameter k This k value is the logarithm to base 2 of the Nside parameter.
healpixSteradians( k )
Returns the solid angle in steradians of each HEALPix pixel at a given order.
healpixSqdeg( k )
Returns the solid angle in square degrees of each HEALPix pixel at a given order.
steradiansToSqdeg( sr )
Converts a solid angle from steradians to square degrees.

The unit sphere is 4*PI steradians = 360*360/PI square degrees.

sqdegToSteradians( sqdeg )
Converts a solid angle from square degrees to steradians.

The unit sphere is 4*PI steradians = 360*360/PI square degrees.

htmLevel( pixelsize )
Gives the HTM level parameter suitable for a given pixel size.
htmResolution( level )
Gives the approximate resolution in degrees for a given HTM depth level.
SQDEG
Solid angle in steradians corresponding to 1 square degree.


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STILTS - Starlink Tables Infrastructure Library Tool Set
Starlink User Note256
STILTS web page: http://www.starlink.ac.uk/stilts/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk