[GRASSLIST:937] Re: Ellipsoid Shift For GRASS Vector Map

[Paul Kelly]

On Mon, 11 Aug 2003, Vidya Kotamraju wrote:

> Hi paul,
>
> Thanks for the earlier response.
>
> As mentioned earlier, I have a GRASS vector map that has been converted
> from a toposheet.This vector map is based on the "everest"
> spheroid/ellipsoid.I have a few GRASS raster maps that are based on the
> "WGS84" ellipsoid.
>
> I need to overlay the vector map on these raster maps.
>
> The raster maps are of 1-kilometer resolution.
>
> I wanted to know the order of error expected by making use of an
> everest-based vector map on a WGS84-based raster map.
>
> what do u expect the order of error to be in this case ?

I don't know; it depends on the local conditions. Usually is a shift of
the order of a few hundred metres but it might be more or less depending
on the local circumstances. If you find somebody who can answer that
question, they would probably also be in a position to provide you with
the datum shift parameters you need to do the transformation in GRASS.