[Xastir] Georeferencing shapefiles.

[J. Lance Cotton]

That's quite a pickle you're in...

I would imagine that the right steps to take would involve the ogr2ogr 
utility included in GDAL/OGR

http://www.remotesensing.org:16080/gdal/ogr/

The README.MAPS file for Xastir has some rudimentary instructions for 
using ogr2ogrm, but they all involve moving from a known datum to a 
different known datum. If you could construct your own datum definition, 
OGR might be able to use that, but that's probably way beyond what 99% 
of us here could do...

The non-free program ArcInfo (from ESRI) may be able to do this easier. 
I think you can lay down a raster file and use it to move and scale 
vectors. Unfortunately, it's quite expensive.

A shapefile just contains numbers -- Xastir expects those numbers to be 
lat/longs. I got shapefiles from my city that were using a 'stateplane' 
datum, which is "distance in feet relative to a specific point", and 
there are hundreds of these specific points -- I had to find the right 
code for South Central Texas, which defines the reference point. Luckily 
I just told ogr2ogr the region and it did all the translation.

-Lance KJ5O

James Ewen wrote:
> So, here I sit with a problem on my hands.
>  
> I have been able to determine that the shapefiles I have are not tied to
> anywhere upon the face of the earth.
>  
> 
>>The original "Blackfoot" files were created as dgn files (Microstation) 
>>by another person, without being geo-referenced. I imported them into
>>shapefile format. The shapefiles are not georeferenced. 
> 
> 
> I guess that if shapefiles can be created using 'relative' coordinates,
> there must be a way to tie them to a 'real world' location. I just need to
> figure out how to do that!
> 
> James
> 
> 


-- 
J. Lance Cotton, KJ5O
joe at lightningflash.net
http://map.findu.com/kj5o-12
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