Dear all,
I have a shapefile which is in CRS ESRI:37203 [1], which is defined in
the prj file as
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]]
The corresponding proj.4 definition (as defined in the esri epsg-codes
file in /usr/share/proj/)
+proj=longlat +a=6377301.243 +b=6356100.230165384 +no_defs
And when I create a location based on this shapefile, the projection
information is:
-PROJ_INFO-------------------------------------------------
name : GCS_Everest_India_Nepal
a : 6377301.243
es : 0.006637846068423442
proj : ll
no_defs : defined
-PROJ_UNITS------------------------------------------------
unit : degree
units : degrees
meters : 1.0
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?
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]
+proj=longlat +a=6377301.243 +b=6356100.2284
+towgs84=295,736,257,0,0,0,0 +no_defs
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?
Regards,
Paulo
[1] https://epsg.io/37203
[2]
https://disqus.com/home/discussion/qgistutorials/georeferencing_topo_sheets_and_scanned_maps/#comment-1426454689
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