#35: Verify and uncomment Swiss datum parameters --------------------------+------------------------------------------------- Reporter: neteler | Owner: grass-dev@lists.osgeo.org Type: defect | Status: new Priority: major | Milestone: 6.4.0 Component: default | Version: unspecified Resolution: | Keywords: Platform: Unspecified | Cpu: Unspecified --------------------------+------------------------------------------------- Changes (by swisstopoum):
* platform: => Unspecified * cpu: => Unspecified Comment: CH1903 and CH1903+ are basically the same system (only defined a little bit differently). The problem is only the realisation of the system (CH1903/LV03 by triangulation ; CH1903+/LV95 by GPS). The differences between the 2 systems are in the order of 1.5 m in maximum. Today we don't recommend the use of the 7 parameter transform any more. So please - whenever possible - don't use them. For the transformation from CH1903+ to ETRS89 we use officially the following 3 parameters: dX=674.374 m, dY=15.056 m; dZ=405.346 m. If necessary, you can model the differences between CH1903+ and CH1903 with a distortion grid in the NTv2 format. This grid can be downloaded here: [http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/ lv03-lv95/chenyx06/distortion_grids.html] More information on the Swiss system and projection can be found here: [http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/sys/refsys.parsysrelated1.2487.downloadList.78978.DownloadFile.tmp/swissprojectionen.pdf] In this document you find all the necessary formulas and parameters - as well as some examples. I revised this document in the meantime - but could not put it on the web yet. It contains some more explanations and more complete examples. Look for the revision date of the document: It should be 'october 2008'. If you need it right now, please contact me. Urs -- Ticket URL: <http://trac.osgeo.org/grass/ticket/35#comment:2> GRASS GIS <http://grass.osgeo.org>
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