Subroutine: IRPL_CORNERS.
Purpose: Calculate plate corners in plate-referenced coordinates.
File: irpl_standard.shl.
Author: 85 Jul 19 Uwe Peppel.
Use:
call IRPL_CORNERS (
size I doubleprecision(2),
corner O doubleprecision(3,4).
)
size long. and lat. length of a plate edge in radians
(= great circle angular distance),
corner xyz of the four corners of the plate in plate-
referenced coordinates.
Description:
The plate-referenced coordinate system is a rectangular
system having the plate center at its x-axis. The y-axis
points to the top of the plate.
IRPL_CORNERS accepts any value for SIZE. In practice the
maximum value for SIZE should be pi/2, which is a plate
covering one half of the whole sky.
The corners are counted anti-clockwise when the x-y-z-system
is taken to be right handed and the plate is seen from outside
the unit-sphere, beginning at the corner with y and z coordinates
both having positive values. With this convention the top
of the plate consists of the corners 1 and 4.
Updates:
900501 Sjag Steensma; documentation only.
900926 DK, change plate definition