[OSRS-PROJ] cs2cs and datum shift]

Duncan Agnew agnew at bilby.ucsd.edu
Mon Aug 26 12:33:23 EDT 2002


	This is not a bug, at least not a deep one.
	The problem is that you have applied the scaling parameter twice;
	if you set this (the 44 in the +towgs setting) to 0 there is no
	problem (inverse of forward is the original). So, it should be set
	to -44 in the inverse to give the right answer. Since a scale
	change (mostly) inflates the Earth, the problem shows up in the
	I do see errors in the forward/inverse pair as the scale factor exceeds
	50 ppm, but not for 44 ppm.
Duncan Agnew
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