This section is partially derived from ``Basic definitions for the USNO and NRL Optical Interferometers'' by D. Buscher.
A baseline vector is oriented from telescope 1 to telescope 2, i.e. the baseline coordinates are the coordinates of station 2 minus the coordinates from station 1. In the aperture plane, the coordinate increases to the East, and the coordinate increases to the North. (Remember though that coverages are plotted in as seen on the sky, so that the source structure and visibility function can be easily superposed.)
In PEARL, a map on the sky is allocated with the -coordinate corresponding to RA, which increases to the left (East). The relationship between visibility and map is then