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7.1.3 sky3d: Spherical Polar Matching

matcher=sky3d values*='<ra/degrees> <dec/degrees> <distance>'
              params='<error/Units of distance>'
              tuning='<scale-factor>'
values*:
  • ra/degrees: Right Ascension
  • dec/degrees: Declination
  • distance: Distance along the line of sight
params:
  • error/Units of distance: Maximum Cartesian separation for match
tuning:
  • scale-factor: Scaling factor to adjust bin size; larger values mean larger bins. Minimum legal value is 1.

The sky3d matcher compares positions in the volume of the sky taking account of distance from the observer. The position in three-dimensional space is calculated for each row using the ra, dec and distance as spherical polar coordinates, where distance is the distance from the observer along the line of sight. Rows are considered to match when their positions in this space are within error units of each other. The units of error are the same as those of distance.

As with sky matching, other longitude/latitude coordinate pairs may be used in place of right ascension and declination.


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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