Next Previous Up Contents
Next: Arithmetic
Up: General Functions
Previous: General Functions
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.
Next Previous Up Contents
Next: Arithmetic
Up: General Functions
Previous: General Functions
TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page:
http://www.starlink.ac.uk/topcat/
Author email:
m.b.taylor@bristol.ac.uk
Mailing list:
topcat-user@jiscmail.ac.uk