[Proj] Projection of SHP file nightmare.

Frank Warmerdam fwarmerdam at gmail.com
Tue Jul 19 14:21:23 EDT 2005

On 7/19/05, Dave Sampson <gis at watersheds.ca> wrote:
> Problem:
> ----------------
> Wanting to display various shape files (and a DEM raster) that use
> varying projection or that are un-projected on a X-Y grid. The X-Y grids
> I believe I could guess at a few potential projections. The challenge
> has been to get them to all show up together.
> using GRASS I can get each to display on their own and have followed all
> the docs, mailing lists etc for all the sotware that I'm using. Is there
> another way?
> I know the *.prj files hold projection data. Can you 'trick' the files
> by editing those?


If you want to show a variety of data together the easiest way (in
my opinion) would be to convert them all to geographic lat/long. 
If your shapefiles have proper .prj files associated with them already,
you can convert them to WGS84 using a commandline like:

 ogr2ogr -t_srs WGS84 out.shp in.shp

You could also try and pick a sensible projected coordinate system
to convert them all too, but this can be a bit tricky if you have data
over a large area. 

In case you don't know, ogr2ogr is part of GDAL/OGR (and available
in FWTools - http://fwtools.maptools.org). 

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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