iraf.net

NUMBER:	270
MODULE:	imshift, magnify, xregister, geotran
SYSTEM:	V2.10
DATE:	Fri Dec  9 10:48:34 MST 1994
FROM:	davis

BUG:    Flux may not be conserved when the IMSHIFT, MAGNIFY, XREGISTER, or
	GEOTRAN tasks are run on undersampled data using the spline3
	interpolant.  In the worst case situation, completely undersampled
	data, fractional y shifts of 0.4-0.6, and placement near the top or
	bottom of the data buffer, the discrepancy is ~ +/- 0.3%. For
	well-sampled data the discrepancy is negligible. For y shifts which
	are exactly 0.0 there is no problem.

	The cause of the problem was that the number of edge lines being
	allocated for the spline3 buffers was too small for undersampled
	data and some of the power in the high frequency components of the
	interpolant was being lost.

STATUS:	Fixed for next release of iraf.