[Qgis-user] Does DWG work in 3.22? - RE: importing dwg/dxf
Stefan Giese (WhereGroup)
stefan.giese at wheregroup.com
Mon Nov 29 22:44:41 PST 2021
An other python based possibility would be to use ezdxf which gives you
access to all or only special DWG/DXF entities and convert them directly
into GIS vector data: https://ezdxf.readthedocs.io/en/stable/
Am 29.11.2021 um 18:36 schrieb Wolfgang Meinolf:
>
> Hi,
>
> I gave up to import DWG directly. I always convert them with ODA File
> Converter 20.8.0 to 2018 ASCII DXF, which I then import using QGIS
> DWG/DXF import feature. Only problem ism that large DXF i.e. including
> ALKIS Layers take ages for the import. In this case I drag&drop the
> DXF into qgis and filter the required Layers manually. In this case
> unfortunately the symbology is gone. All DWG are customer provided, I
> have no ACAD available.
>
> Best regards
>
> Wolfgang
>
> *Von:* Qgis-user <qgis-user-bounces at lists.osgeo.org> *Im Auftrag von
> *Nicolas Cadieux
> *Gesendet:* Montag, 22. November 2021 18:55
> *An:* Jeff Sonnentag <jsonnentag at llenviroinc.com>; Bernd Vogelgesang
> <bernd.vogelgesang at gmx.de>; Greg Troxel <gdt at lexort.com>; Boaz Bar
> Ilan <boazprosie at gmail.com>
> *Cc:* qgis-user <qgis-user at lists.osgeo.org>
> *Betreff:* Re: [Qgis-user] Does DWG work in 3.22? - RE: importing dwg/dxf
>
> Hi,
>
> The GDAL/ORG library works with Open Design Alliance Teigha library.
> They have a support for R13-15, R2004, R2007, R2010, R2013 and R2018
> but since Autocad is a closed format, then all of this is basically
> the result of reversed engineering. DXF is an open format so that is
> easier to deal with.
>
> I believe that the drag and drop functions for DWG and DXF uses the
> libopencad drivers (and that is limited to r2000 or ACAD1015)) (at
> least in QGIS 3.20) so if you did drag and drop a correct file format,
> then the DWG worked.
>
> It's my personal experience that anything past R15 (2000) will be
> buggy in QGIS but you can also open those files using the project >
> import/export > import layer from DWG/DXF. For some reasons, some DWG
> files cannot be dragged and dropped but can be imported via the
> project import function. This has the advantage of keeping the Autocad
> styling. I guess this function probably uses the Open Design Alliance
> Teigha library and not the libopencad drivers as it will open files
> that I cannot drag and drop??? Looks like those functions are not
> available via the python API nor the Processing toolbox either:(
>
> Anyways, when that fails (about 50% of the time on very big files), I
> save the DWG to DXF and that either fixes the file or makes it more
> compatible with the driver. IMHO, Exporting dwg to shp file is the
> only real interesting feature of AutoCAD Map3D. The last version I
> regularily worked with has probably 2013-15 so maybe they have updated
> the product since.
>
> https://knowledge.autodesk.com/support/autocad/learn-explore/caas/sfdcarticles/sfdcarticles/AutoCAD-drawing-file-format.html
>
> https://docs.qgis.org/3.22/en/docs/user_manual/managing_data_source/opening_data.html?highlight=dwg#importing-a-dxf-or-dwg-file
>
> Nicolas
>
> On 2021-11-21 11:06 p.m., Jeff Sonnentag wrote:
>
> Somebody must get the same quality of “engineering” that we do
> here. :D
>
> The last item received was in feet and aligns with California
> State Plane Zone 6, but they chopped off the first digit of both
> “X” and “Y” for everything. Who knows why. Maybe things run
> faster for them with 6 digit coordinates rather than 7 digit ones
> like you mentioned. (???)
>
> Anyway, when I tried the simple drag and drop into QGIS 3.22 it
> never worked. Always an error message about invalid data, even
> after I used DWG Trueview to convert it to the oldest possible
> versions (97/98 and 2000). I did manage to get it in AFTER
> converting the DWG to a DXF with an online conversion site. That
> DXF could be drug (I hate the word “dragged” – seems along the
> lines of “runned”) into QGIS and appeared OK. Export to a
> shapefile and then do some affine adjustment magic and things can
> be worked with.
>
> Is there a reason that a DWG can’t be dropped into QGIS 3.22 but a
> DXF can? Are there some DWG versions that just don’t work? I
> thought I got a DWG to appear OK in 3.16, but maybe I just
> imagined it and used a DXF before too. . . .
>
> *From:* Qgis-user <qgis-user-bounces at lists.osgeo.org>
> <mailto:qgis-user-bounces at lists.osgeo.org> *On Behalf Of *Bernd
> Vogelgesang
> *Sent:* Sunday, November 21, 2021 10:53 AM
> *To:* Nicolas Cadieux <njacadieux.gitlab at gmail.com>
> <mailto:njacadieux.gitlab at gmail.com>; Greg Troxel <gdt at lexort.com>
> <mailto:gdt at lexort.com>; Boaz Bar Ilan <boazprosie at gmail.com>
> <mailto:boazprosie at gmail.com>
> *Cc:* qgis-user <qgis-user at lists.osgeo.org>
> <mailto:qgis-user at lists.osgeo.org>
> *Subject:* Re: [Qgis-user] importing dwg/dxf
>
> On 21.11.21 15:35, Nicolas Cadieux wrote:
>
> Hi,
>
> .dwg or dxf have no CRS. They can be in inches, feet, mm, cm,
> m... Usually meter in a local CRS like a local WGS84 UTM ZONE
> is used. You can usually find this in the metadata if available.
>
> Nicolas
>
> I have no deep technical insight into dwg or dxf, but I am pretty
> sure that those CAD-"products" are able to be produced with valid
> coordinates, fitting to a common CRS. Most people using
> CAD-systems simply seem to be either too stupid for that, or just
> do not care.
>
> One of the reasons, CAD-"data" is produced with a local reference
> system instead with a normal CRS is, according to an CAD-operator
> I once asked about this, that some CAD-systems just slow down to
> in-operability when using real-world coordinates because of the
> huge numbers, compared to the small coordinates in their own system.
>
> So, I would not even try to fix this, but instead ask those guys
> to stop scratching their balls and better send you proper
> real-world data and tell you which CRS they are in . The handling
> of this "data" is punishment enough afterwords.
>
> Hope my dislike for this "technology" was not too obvious ;)
>
> Cheers,
>
> Bernd
>
>
> On 2021-11-21 9:07 a.m., Greg Troxel wrote:
>
>
> Boaz Bar Ilan<boazprosie at gmail.com>
> <mailto:boazprosie at gmail.com> writes:
>
>
>
> i always have problem importing dwg or dxf . the
> layers dont fit the
> coardinations and even when i set the layers crs it
> doesnt work.
>
> I am far from an expert, but recently tried to deal with a
> dwg.
>
> My impression is that they are almost always in local
> coordinates, and
> the path to success is something like using GeoScience
> plugin to define
> a local CRS based on control points where you know global
> coordinates
> and local, and then to use that CRS for the data.
>
> I recently imported some "PNEZD" data (csv with point it,
> northing,
> easting, vertical, and description, all in an unspecified
> local grid,
> from a total station data collector) and used geoscience
> to align it
> wtih RTK obsservations of a few points, and things fit
> quite well.
>
> How are you getting dwg? Are you using the proprietary
> dwg library with
> gdal, or is there some open source path?
>
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> --
> Nicolas Cadieux
> https://gitlab.com/njacadieux
>
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