[GRASS-dev] Re: [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
-------------------------------------+--------------------------------------
 Reporter:  hamish                   |       Owner:  grass-dev@…              
     Type:  defect                   |      Status:  new                      
 Priority:  critical                 |   Milestone:  6.4.2                    
Component:  Projections/Datums       |     Version:  svn-releasebranch64      
 Keywords:  location wizard, g.proj  |    Platform:  All                      
      Cpu:  All                      |  
-------------------------------------+--------------------------------------
Changes (by hamish):

  * platform:  MSWindows XP => All
  * cpu:  x86-32 => All


Comment:

 wingrass nightly build:
 > `g.proj proj4='+proj=longlat +datum=nad83' datumtrans=-1`
 > but no results printed!

 ok, I think I understand the problem. It's the same broken proj 4.7.1svn
 EPSG file:

 source:grass/trunk/general/g.proj/datumtrans.c#L48
 source:grass/trunk/lib/proj/datum.c#L111

 -> g.proj checks for the datum using `GPJ__get_datum_params()` which
 returns 1 for datum name found, and 2 for datum name found with datum
 transform options already specified.

 since the current PROJ.4 svn copy of the epsg file has had +towgs84 terms
 added in bulk, and +datum names removed, I suspect the result is coming
 back as "2", but the if(force){print the available options} in g.proj's
 datumtrans.c is only being run if the result is == "1" (ie datum name
 found, but no info about which of the available transforms to use). That
 behavior seems reasonable enough.

 I've added another debug message in svn to check the result of the datum
 query and confirm the above theory.


 if so, the fix remains to be repairing the epsg file in proj4 svn, and/or
 sticking with released proj 4.7.0.

 (noticed on wingrass because that's built with development proj 4.7.1svn)


 Hamish

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Ticket URL: <https://trac.osgeo.org/grass/ticket/1452#comment:8>
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