[GRASS-dev] Re: [GRASS GIS] #1536: add EPSG:900913 to location wizard

GRASS GIS trac at osgeo.org
Mon Jan 16 06:54:52 EST 2012

#1536: add EPSG:900913 to location wizard
 Reporter:  timmie                   |       Owner:  grass-dev@…              
     Type:  enhancement              |      Status:  new                      
 Priority:  normal                   |   Milestone:  6.4.2                    
Component:  Projections/Datums       |     Version:  6.4.2 RCs                
 Keywords:  google projection, epsg  |    Platform:  MSWindows XP             
      Cpu:  Unspecified              |  
Changes (by hamish):

  * keywords:  => google projection, epsg
  * type:  defect => enhancement


 after originally reacting with horror, AFAIU the epsg people have given up
 the fight and issued the spherical mercator with wgs84's major ellipsoid
 radius its own epsg code. So this will be fixed in time with a new version
 of the epsg file and the only action needed is to wait. it is not
 recommended to use spherical merc for real analysis, only data transfer
 and matching visual cartography.
 it is designed to be very fast on their servers, not to seek the ultimate
 perfection in geodesy. (fair enough for their needs)

 I think g.proj works but it isn't listed in the wizard as the wizard just
 parses the main epsg file while g.proj uses the PROJ4 library which also
 checks the esri.extra file that contains the "Chris's funny" projection.

 be careful calling it the 'google' projection, their google maps slippy
 tile projection is a slightly different thing again (and even more
 distorted). each row of tiles has its own slightly different projection!
 the two are related but get confused a lot.


Ticket URL: <https://trac.osgeo.org/grass/ticket/1536#comment:1>
GRASS GIS <http://grass.osgeo.org>

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