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

Clifford J Mugnier cjmce at lsu.edu
Sun Sep 22 17:27:38 EST 2013

```The differences could be the "sense" of the rotation angles.  Consider changing the signs and see what happens ...

Clifford J. Mugnier, c.p., c.m.s.

Chief of Geodesy

LSU Center for GeoInformatics (ERAD 266)

Dept. of Civil Engineering (P.F. Taylor 3531)

LOUISIANA STATE UNIVERSITY

Baton Rouge, LA  70803

Research: (225) 578-4578

Cell:             (225) 328-8975

fellow emeritus, asprs

member, apsg

________________________________
From: proj-bounces at lists.maptools.org [proj-bounces at lists.maptools.org] on behalf of Nick Ves [vesnikos at gmail.com]
Sent: Sunday, September 22, 2013 4:53 PM
To: proj at lists.maptools.org
Subject: [Proj] gis.SE: Huge differences between results for 7-param datum transform

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

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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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