[GRASS-dev] [GRASS GIS] #1452: wx location wizard doesn't ask for datum transform options because proj4 4.7.1's epsg file is broken

[GRASS GIS]

#1452: wx location wizard doesn't ask for datum transform options because proj4
4.7.1's epsg file is broken
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  Reporter:  hamish              |       Owner:  grass-dev@…              
      Type:  defect              |      Status:  reopened                 
  Priority:  major               |   Milestone:  6.4.3                    
 Component:  Projections/Datums  |     Version:  svn-releasebranch64      
Resolution:                      |    Keywords:  location wizard, g.proj  
  Platform:  All                 |         Cpu:  All                      
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Changes (by hamish):

  * priority:  critical => major
  * status:  closed => reopened
  * resolution:  fixed =>


Comment:

 Hi,

 Reopening, lowering priority, & taking ownership of the ticket until I've
 had a chance to thoroughly test it. It all seems to be working now, but I
 don't think I'll be comfortable with it until I've audited the entire (new
 bits of the) code chain, and it's an important enough thing that I'd like
 to spend a little bit of my "copious free time" doing that.

 pkelly wrote:
 > Hmmm, I have just read through the bug thread and am confused by all
 > the discussion about PROJ. g.proj does not use PROJ at all (nor any
 > files from the PROJ distribution) and strings passed with the proj4=
 > option are interpreted by GDAL/OGR functions, so I don't see how
 > changes to PROJ an fix the original problem in this report.

 What you are missing is that the wxPy location wizard takes the parameters
 it is told and converts/expands them to a proj4 string, and runs g.proj
 using that string. That process can be lossy, and/or not work for things
 which grass's projection engine supports(knows about) but the installed
 version of proj4/gdal does not.
 g.setproj is just fine, the problem was if you started with an epsg code
 with the epsg file from proj 4.7.1svn, but Frank cleared that up before
 releasing 4.8.0.
 I'll have to dig through grass's datum table (for example) to demonstrate
 the corner cases which I'm thinking about.

 ~unrelated to the main set of cases I'm thinking of, the google spherical-
 merc epsg:900913 and other oddballs in the extra-epsg files are good test
 cases to make sure everything that needs to be is being picked up.


 thanks,
 Hamish

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Ticket URL: <https://trac.osgeo.org/grass/ticket/1452#comment:43>
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