[Qgis-user] Does DWG work in 3.22? - RE: importing dwg/dxf

[Jeff Sonnentag]

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> On Behalf Of Bernd Vogelgesang
Sent: Sunday, November 21, 2021 10:53 AM
To: Nicolas Cadieux <njacadieux.gitlab at gmail.com>; Greg Troxel <gdt at lexort.com>; Boaz Bar Ilan <boazprosie at gmail.com>
Cc: qgis-user <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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