[Proj] gis.SE: Huge differences between results for 7-param datum transform

[Nick Ves]

Hi List,

I've encounter the following question in gis.stackexcange [0] which is a
bit theoretical and interesting.

It has to do about coordinate shifting between gdal and two other
commercial applications and I am too wondering whats happening.

I would be very interested If someone could provide an insightful answer on
what is happening

Nikos


[0]
http://gis.stackexchange.com/questions/72173/huge-differences-between-results-for-7-param-datum-transform

I'm trying to transform a WGS84 lat/lon point

11d42'32.10629" E 5d12'56.75371" S

in three different software packages (Proj4, GeoTrans and Leica GeoOffice)
but I receive very big differences between the results - around few hundred
meters in X and Y! Note that these variations appears only with 7
parameters not with 3.

*Proj4*

cs2cs +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs +to +proj=utm
+zone=32 +ellps=clrk80
+towgs84=178.3,316.7,131.5,-5.278,-6.077,-10.9792,-19.166 +south +units=m
+no_defs

------------------------------

*GeoTrans*

Delta X 178.3
Delta Y 316.7
Delta Z 131.5
Rot X -5.278
Rot Y -6.077
Rot Z -10.9792
SF = -19.166 / 0.999980834 (0.000019166)

------------------------------

*Leica GeoOffice*

Screenshot: http://imgur.com/cOTRuQB
------------------------------

The results are respectively:

   1. 800392 9422525
   2. 800306 9422840
   3. 800941 9422891

I believe all the 3 packages use same mathematical methods for 7-param
transform (Bursa-Wolf method). What could be the cause of this huge
variation?
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