Transform tangent plane coordinates into spherical
coordinates (double precision)
CALL sla_DTP2S (XI, ETA, RAZ, DECZ, RA, DEC)
tangent plane rectangular coordinates (radians)
spherical coordinates of tangent point (radians)
spherical coordinates (radians)
The projection is called the gnomonic projection; the
Cartesian coordinates are called
standard coordinates. The latter
are in units of the distance from the tangent plane to the projection
point, i.e. radians near the origin.
When working in rather than spherical coordinates, the
equivalent Cartesian routine sla_DTP2V is available.