FW: [GRASS-user] DXF to UTM32

[Pablo Carreira]

If your dxf is in a local coordinate system (like old topo drawings) with shifting parameters you can use v.transform or you can put it in place with a CAD software (align) and them import into GRASS.
If it already have an utm coordinate and you want to change the reference system (datum) create the coresponding location import, change location and them v.proj (should be no problem).

I work with a lot of CAD drawings and charts with GRASS and here is a very usefull advice:
The fundaments of areas, boundary and lines in CAD and GIS are different, before importing a drawing into a GIS try to make it clean and "GIS like", ex. make two areas share the same boundary. Also import only the objects of interest, do not import text, paper layout or hatches.

I'am sorry about my english.

Pablo Torres Carreira




> Date: Wed, 18 Nov 2009 14:28:46 +0200
> Subject: Re: [GRASS-user] DXF to UTM32
> From: maris.gis at gmail.com
> To: raffaele.morelli at gmail.com
> CC: grass-user at lists.osgeo.org
> 
> Hello,
> be care full with QGIS layer CRS definitions. By default QGIS will
> assign WGS84 as layers CRS if layer lacks CRS definition or definition
> is bogus. Use ogrinfo -ro -so MyFile to check files CRS. Still IIRC
> DXF doesn't contain CRS definition - You have to look into metadata
> provided with Your DXF file (if You have metadata) or do Your best
> guess based on DXF data location (i.e. DXF file from Latvia most
> likely will contain data in LKS-92/TM CRS).
> If You are interested in transforming DXF ?? to UTM, You can also try
> to use ogr2ogr and then import result into GRASS for
> analysis/processing. ogr2ogr provides -s_srs option where You can
> specify source CRS.
> 
> Hope this helps,
> Maris.
> 
> 2009/11/18, Raffaele Morelli <raffaele.morelli at gmail.com>:
> > 2009/11/11 Micha Silver <micha at arava.co.il>
> >
> >>  Raffaele Morelli wrote:
> >>
> >> Hi you all,
> >>
> >> how can I transform a dxf (imported with v.in.dxf) layer in utm32
> >> coordinates system? I am currently doing some trials with v.transform with
> >> no success.
> >>
> >>  Is the dxf in some coordinate system?
> >> If yes, then make a location based on that CRS, import the dxf into that
> >> location, then v.proj inot the UTM location.
> >> If not, then make an X-Y based location, import the dxf there, then again
> >> v.proj into your UTM location.
> >>
> >
> > I have created an XY based location but whe using v.proj grass fails
> > complainig about PROJ file not found... so still stucked
> >
> > Opening the dxf (converted using dxf2shp plugin) in Qgis reports that is a
> > "+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs"
> >
> > regards
> > -raffaele
> >
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