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

[Bill Binko]

On Wed, 6 Jul 2005, Frank Warmerdam wrote:

> On 7/6/05, Bill Binko <bill at binko.net> wrote:
> > 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. 
> 

I would simply like to be able to use HARN data in Mapserver layers, 
PostGIS datasets, and rasters manipulated by GDAL.  I don't even mind if 
it's limited to being able to convert from NAD 83 HARN to NAD83 without 
introducing any errors.  Perhaps that is possible now, but when I asked, I 
was told "Just use NAD 83 -- it's close enough".

So, yes, it would be nice to be able to have a +datum=HARN, but generally, 
I just want to be able to use HARN data in Mapserver et al.  I don't mind 
a few hoops I have to jump through.

Bill