[GRASS-user] writing MicroStatioin DGN files

[gisfisch at t-online.de]

Markus,

thank you very much for your answer.
In your example, you used any GRASS map with any columns. They can obviously not be written to DGN (eg. MAJORRDS_). 
Please note that in my workflow, the DGN is imported into GRASS, then processed and then written back. So the GRASS map must have the correct DGN colums because it was created from DGN by GRASS itself.
When I import a DGN and use db.select right after that, I get:

cat|Type|Level|GraphicGroup|ColorIndex|Weight|Style|EntityNum|MSLink|Text|ULink
1|17|1|0|2|2|0|||423|{ "32047": [ { "size": 8, "raw": [ "0x1003", "0x7d2f", "0x0871", "0x0000" ], "type": "ODBC" } ] }
2|17|1|0|2|2|0|||424|{ "32047": [ { "size": 8, "raw": [ "0x1003", "0x7d2f", "0x0872", "0x0000" ], "type": "ODBC" } ] }
3|17|1|0|2|2|0|||426|{ "32047": [ { "size": 8, "raw": [ "0x1003", "0x7d2f", "0x0873", "0x0000" ], "type": "ODBC" } ] }

Then, when I use v.out.ogr -s to skip the cat column, the driver complains about the Type column. But that one is undoubtedly part of the fixed DGN schema, as you can see above.
I understand that writing any random colums can not work, but I try to write exactly the DGN schema.

Please let me emphasize again that it worked fine for years in GRASS 7.0.
I assume there is a bug in the younger GRASS versions. Or has anybody succeeded in writing out DGNs?

Best regards, Uwe


-----Ursprüngliche Nachricht-----
Von: Markus Neteler <neteler at osgeo.org> 
Gesendet: Freitag, 12. Januar 2024 18:14
An: gisfisch at t-online.de
Cc: grass-user at lists.osgeo.org
Betreff: Re: [GRASS-user] writing MicroStatioin DGN files

On Fri, Jan 12, 2024 at 10:12 AM gisfisch--- via grass-user <grass-user at lists.osgeo.org> wrote:
>
> Hello list,
>
> I try to write MicroStation V7 DGN files in GRASS 7.8.7. using v.out.ogr.
>
> The same has been working for me without problems since years in GRASS 7.0.
>
> Now I get the following messages:
>
> v.out.ogr -s input=mymap at tempwork output=C:\Users\Documents\mydgn.dgn 
> format=DGN
>
> ERROR 6: CreateField() not supported by this layer.
> ERROR: Unable to create column <Type>
>
> The DGN file is created, but there are no data written to it.
>
> Please help, because writing those files is critical for my workflow.
>

I have made a test with the North Carolina sample dataset:

GRASS nc_spm_08_grass7/user1:~ >
v.out.ogr input=roadsmajor type=line output=/tmp/roadsmajor.dgn format=DGN  --o ERROR 6: CreateField() not supported by this layer.

ERROR: Unable to create column <cat>

==> so, add -s flag to supress "cat".

v.out.ogr input=roadsmajor type=line output=/tmp/roadsmajor.dgn format=DGN  --o -s ERROR 6: CreateField() not supported by this layer.

ERROR: Unable to create column <MAJORRDS_>

Apparently that column is also disliked.

Googling shows:
https://lists.osgeo.org/pipermail/gdal-dev/2006-February/008089.html
"The CreateField() messages are expected with DGN output.  The  DGN format has a fixed schema and doesn't support user defined  fields.
"

Looking further in the OGR DGN driver docs shows:
https://gdal.org/drivers/vector/dgn.html

"Creation Issues

2D DGN files may be written with OGR with significant limitations:

- Output features have the usual fixed DGN attributes. Attempts to create any other fields will fail.
- ...
- A seed file must be provided (or if not provided, $PREFIX/share/gdal/seed_2d.dgn will be used). Many aspects of the resulting DGN file are determined by the seed file, and cannot be affected via OGR, such as initial view window.
- ...
"

I assume that in your case the attribute table names need to follow this fixed DGN attributes scheme.

HTH,
Markus


--
Markus Neteler, PhD
https://www.mundialis.de - free data with free software https://grass.osgeo.org https://neteler.org/blog