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<div class="moz-cite-prefix">On 18-03-17 10:06, Paulo van Breugel
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:d4c7ad21-08b9-a04b-ac7e-be4125ca3a85@gmail.com">Dear
all,
<br>
<br>
I have a shapefile which is in CRS ESRI:37203 [1], which is
defined in the prj file as
<br>
<br>
GEOGCS["GCS_Everest_India_Nepal",DATUM["D_Everest_India_Nepal",SPHEROID["Everest_Definition_1962",6377301.243,300.8017255]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]
<br>
<br>
<br>
The corresponding proj.4 definition (as defined in the esri
epsg-codes file in /usr/share/proj/)
<br>
<br>
+proj=longlat +a=6377301.243 +b=6356100.230165384 +no_defs
<br>
<br>
And when I create a location based on this shapefile, the
projection information is:
<br>
<br>
-PROJ_INFO-------------------------------------------------
<br>
name : GCS_Everest_India_Nepal
<br>
a : 6377301.243
<br>
es : 0.006637846068423442
<br>
proj : ll
<br>
no_defs : defined
<br>
-PROJ_UNITS------------------------------------------------
<br>
unit : degree
<br>
units : degrees
<br>
meters : 1.0
<br>
<br>
Question 1: Now, I can import a shapefile or raster layer in
latlon/WGS84 (EPGS: 4326) without reprojection. GRASS thus assumes
the projection is identical, even if they are not? Why is that?
<br>
<br>
The proj.4 definition above is missing the shift w.r.t. the WGS84.
The correct proj.4 definition for EPGS 37203 would be [2]
<br>
<br>
+proj=longlat +a=6377301.243 +b=6356100.2284
+towgs84=295,736,257,0,0,0,0 +no_defs
<br>
<br>
Question 2: In QGIS it is possible to define a custom CRS using
the above. Can I do this in GRASS as well, and if so, how? Or can
/ should I add this to the datum information files in
$GISBASE/etc/proj/ogr_csv?
<br>
<br>
<br>
Regards,
<br>
<br>
Paulo
<br>
<br>
<br>
[1] <a class="moz-txt-link-freetext" href="https://epsg.io/37203">https://epsg.io/37203</a>
<br>
[2]
<a class="moz-txt-link-freetext" href="https://disqus.com/home/discussion/qgistutorials/georeferencing_topo_sheets_and_scanned_maps/#comment-1426454689">https://disqus.com/home/discussion/qgistutorials/georeferencing_topo_sheets_and_scanned_maps/#comment-1426454689</a><br>
</blockquote>
<br>
A link that provides further relevant information<br>
<br>
<style type="text/css">p { margin-bottom: 0.25cm; direction: ltr; line-height: 120%; text-align: left; }p.western { font-family: "Calibri",sans-serif; font-size: 11pt; }p.cjk { font-family: "Calibri"; font-size: 11pt; }p.ctl { font-size: 11pt; }a:link { color: rgb(0, 0, 255); }</style><a class="moz-txt-link-freetext" href="https://github.com/klokantech/epsg.io/issues/49">https://github.com/klokantech/epsg.io/issues/49</a><br>
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