WD-DALI-1.1 polygon winding direction

[Felix Stoehr]

Dear all,

after some side-discussions with Marc I believe the following is true:

- STC-S declares clockwise and counterclockwise with respect to the
celestial coordinate frame (north up, east to the left as seen from earth)

- this is consistent with the footprintfineder.py output and thus all
the MAST/ALMA/ESA spectra

- area calculations will be correct in this definition and coordinate frame

- it is a bit counter-intuitive, because it means that anticklockwise
polygons in that definition are clockwise if you look up on the sky from
earth.

It might be worthwile to declare in WD-DALI-1.1 the coordinate system in
which the clockwise/anticlockwise are defined, i.e. in which system to
"hold the clock".

Best regards,

Felix