Astrometry
There are two modes for the output of the astrometric data, in spherical coordinates (figure above) and in rectangular coordinates (below). In both cases the coordinate system has to be specified. In spherical coordinates the usual astrometric parameters with their standard errors can be produced.
Space positions are derived from the direction cosines of the spherical coordinate, divided by the parallax in mas, giving Cartesian coordinates in kpc, and rates in km s-1.