datameet
Old SOI index map shapefile projections seem wrong.
Both the old and new SOI projection files are in wgs84 and look like they match. This seems off to me.
https://github.com/datameet/maps/blob/master/Survey-of-India-Index-Maps/OSM_UTM_WGS84/OSM_50K_Index.prj
GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]
https://github.com/datameet/maps/blob/master/Survey-of-India-Index-Maps/OldSystem_Everest_Polyconic/OldSystem_50K_Index.prj
GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]
The best source of information on the old indian datum i have found so far is at https://deeppradhan.heliohost.org/
Can you help me understand exactly what is the problem?
The purpose of these two files is to help someone figure out what Toposheet a location falls in.
The New UTM based OSM maps are in WGS84 datatum anyway, so the projection for that seems fine to me.
While the Older Toposheets were in the Everest or Modified Everest Datum, the files in the https://github.com/datameet/maps/blob/master/Survey-of-India-Index-Maps/OldSystem_Everest_Polyconic folder are just for the sake of figuring out which toposheet a location falls in. We do not take the datum shift into account for this purpose.
Given that the shapefile for the Old system advertises the datum as WGS84 in the .prj file, I was hoping the datum shift calculations were taken into account.
I am trying to look for a source where I don't have to do those calculations myself :)
In the end I am looking for the list of older 1:50000 toposheets which cover the missing/unreleased newer 1:50000 OSM toposheets.
To be clear, the only actionable item here would be documentation.. or may be moving the files to a plain json file instead of a shapefile.