[Proj] How to convert a sphere to ellipsoid with correct datum?
ovv at hetnet.nl
Thu Sep 2 10:25:44 EST 2010
From: peifer <peifer <at> gmx.eu>
Subject: Re: How to convert a sphere to ellipsoid with correct datum?
Date: 2010-09-02 12:41:09 GMT
in practical terms of cs2cs usage (and leaving out the question about the
spherical case), doesn't this simply mean that one has to add +towgs84=0,0,0
on both sides, as I suggested earlier?
Or +towgs84=0,0,0,0,0,0,0 or +towgs84=0,0,0,0,0,0,1. It doesn't seem to
make much of a difference.
cs2cs +proj=latlong +ellps=bessel +to +proj=latlong +ellps=WGS84
10dE 60dN 0.000
cs2cs +proj=latlong +ellps=bessel +towgs84=0,0,0 +to +proj=latlong
10dE 60d0'1.864"N -690.016
This is indeed what you get with a simple conversion from lat-lon on Bessel
1841 to geocentric and then from geocentric to lat-lon on WGS84. If this
conversion makes any sense, one has to judge carefully. Frank is very right
BTW: in my earlier mail I suggested a scaling parameter ds=1.0.
This should be 0. What I meant was a scaling of one, but usually a number in
ppm is asked, which will be added to 1.0 internally by the conversion
Exactly HOW cs2cs works, I don't know. Read the manual or ask Frank.
Oscar van Vlijmen
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