[GRASS-dev] Re: [GRASS GIS] #35: Verify and uncomment Swiss datum parameters

[GRASS GIS]

#35: Verify and uncomment Swiss datum parameters
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  Reporter:  neteler      |       Owner:  grass-dev at lists.osgeo.org
      Type:  defect       |      Status:  new                      
  Priority:  major        |   Milestone:  6.4.0                    
 Component:  default      |     Version:  unspecified              
Resolution:               |    Keywords:                           
  Platform:  Unspecified  |         Cpu:  Unspecified              
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Comment (by hamish):

 Replying to [comment:6 swisstopoum]:
 > Just some comments to this:
 > a) NTv2: I really think it would be fine to support NTv2. There
 > are some countries who apply this approach (it was developped in
 > Canada and then adopted in Australia, France, Germany,...). More
 > and more commercial GIS developpers start to support this option.

 GRASS does and has supported grid transforms for many years.
 You just need the grid file for your country.
 grid files are in $GISBASE/etc/nad/ and /usr/share/proj/.


 > Answer: A 7-parameter transformation is always more accurate
 > than a 3-parameter solution.

 I dare you to say that on the PROJ4 mailing list.

 Different 3,7 term parameter sets will be more or less valid depending on
 where in the country (SRS) you are.
 If anyone is interested, further reading here:
 http://grass.osgeo.org/wiki/Gis_Concepts#Geodesy_and_Cartography


 Hamish

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Ticket URL: <http://trac.osgeo.org/grass/ticket/35#comment:7>
GRASS GIS <http://grass.osgeo.org>