[MetaCRS] Differences between results for 7-param transform

[Paul Nalos]

Hi Svetlozar,

Jan's suggestion (rotation convention - position vector vs. coordinate
frame) is the most probable. Of course, that suggestion can only yield two
unique answers and you have three.

Other possibilities:

The to/from ellipsoids matter a great deal. I'm not familiar enough with
each of these software packages to know if you've configured this
aspect consistently.

Finally, there are (at least) two ways to formulate the 7-parameter
transform: an approximation in very common use, and a more rigorous form.
These can give different answers.

If you get to the point that you want to establish the "right" answer, you
may wish to consult EPSG's 7-2 (http://www.epsg.org/guides/G7-2.html) document
for formulas and worked examples.

Good luck!

Paul Nalos, Safe Software Inc.

> Hello, I have a WGS84 point that I transform to UTM with 7-parameter datum
> transform. I try exactly the same input data in 3 different software
> packages (Proj4, GeoTrans and Leica GeoOffice) but all 3 results differ a
> lot. I'm confused which is correct, which is not and what is the cause of
> this. I posted the whole question and all data on
>
http://gis.stackexchange.com/questions/72173/huge-differences-between-results-for-7-param-datum-transform
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