[Gdal-dev] converting from NAD 83 to NAD 83 HARN

[Frank Warmerdam]

On 7/6/05, Bill Binko <bill at binko.net> wrote:
> On Wed, 6 Jul 2005, Frank Warmerdam wrote:
> 
> ...
> 
> > I think the solution to this issue would be for GDAL to support a WKT
> > extension for specifying grid shift files, as opposed to the TOWGS84
> > method of defining a datum.   I think ESRI WKT already has this feature,
> > so I could do it similarly.  However, this isn't really high on my
> > priority list at this time.
> >
> 
> Frank,
> 
> Is there any way to make this supported by Proj in general?  I have HARN
> data in vector format (in PostGIS and shapefiles) that I'd like to have
> projected more accurately.  I was not aware of the existence of those grid
> shift files (and still don't have any for my coverage area), but I'd
> certainly like to remove those anomalies in my data that I (still) think
> come from the HARN/NonHARN Datum mismatch.

Bill, 

Well, PROJ already supports use of HARN grid shift files via the
nadgrids option, but the user has to manually select the grid files desired.
Were you looking for built-in +datum=HARN support?  Fixes in the epsg
support files for HARN coordinate systems?  These are all possible, but
I don't feel I am familiar enough with HARN file availability or "issues" to
pursue it at this time. 

Best regards,
-- 
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