[GRASS-user] DXF to UTM32

GRASS GRASS user
1

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.

Arranging xshit and yshift leads me near the desired result but there’s still a rotation problem I can’t solve (it seems to me at least)

Any hints?

regards
-raffaele

2

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.

3

2009/11/11 Micha Silver <micha@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

4

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@gmail.com>:

2009/11/11 Micha Silver <micha@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

5

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@gmail.com
To: raffaele.morelli@gmail.com
CC: grass-user@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@gmail.com:

2009/11/11 Micha Silver micha@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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6

On Wed, Nov 18, 2009 at 10:33 PM, Pablo Carreira
<pablotcarreira@hotmail.com> wrote:

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.

Pablo,

you notes are very interesting! Could you add them into a related Wiki page:
http://grass.osgeo.org/wiki/Import_DXF

thanks
Markus

7

From: neteler@osgeo.org
Date: Sun, 22 Nov 2009 12:58:48 +0100

Pablo,

you notes are very interesting! Could you add them into a related Wiki page:
http://grass.osgeo.org/wiki/Import_DXF

I have added them. If someone could review it I would thank.

Regards.

Pablo.

Chegou o Windows 7: Incrivelmente simples! Clique e conheça.