topic Re: Georeference dxf in Civil3D not at correct position after export in Civil 3D Forum

Georeference dxf in Civil3D not at correct position after export

yhofmann7K3UB — Thu, 09 May 2024 11:35:50 GMT

Hi,

I have difficulties with my georeferenced .dxf polymesh file. In civil 3D it looks correctly georeferenced (see image, I use EPSG 2056, which is Switzerland) but when I then export the .dxf and import it to QGIS is it first of all not assigned to a coordinate reference system and when I then select 2056 is it at the totally wrong location (see second image). What do I need to change?

Re: Georeference dxf in Civil3D not at correct position after export

Pointdump — Thu, 09 May 2024 14:28:09 GMT

Hi Ya,

The extents(Bounding Box) of >>>EPSG:2056<<< CH1903+/LV95 -- Swiss CH1903+/LV95 are
MinEasting: 2485071.58 MinNorthing: 1074261.72
MaxEasting: 2837119.8 MaxNorthing: 1299941.79

Your drawing is at the 0,0 origin. So I suspect command GEOLOCATION has claimed yet another victim. I'm not sure how to fix, other than starting over.
Dave

Edit: (Also note PLAN is not set to World anymore.)

Re: Georeference dxf in Civil3D not at correct position after export

yhofmann7K3UB — Thu, 09 May 2024 14:37:51 GMT

Thanks for your reply. So what I try to do is that I have given the dxf and now I simply want to set the origin an the heading/northing. I'm a bit confused why this does not work by simply saying that 0,0,0 of my given dxf is at x,y,z of the 2056 CRS (which I have also given).

Any insight on this are highly appreciated.

Re: Georeference dxf in Civil3D not at correct position after export

AllenJessup — Thu, 09 May 2024 14:58:21 GMT

Was there any UCS set?

Can you share the original drawing?

Re: Georeference dxf in Civil3D not at correct position after export

yhofmann7K3UB — Thu, 09 May 2024 15:18:00 GMT

There was no USC set I believe. Find attached the original file as well as the file where the coordinate information I have given can be seen.

Re: Georeference dxf in Civil3D not at correct position after export

AllenJessup — Thu, 09 May 2024 15:25:09 GMT

Was there an original DWG file? I'd like to try the DXF export workflow.

Re: Georeference dxf in Civil3D not at correct position after export

yhofmann7K3UB — Thu, 09 May 2024 15:33:03 GMT

Unfortunately do I not have access to it.

Re: Georeference dxf in Civil3D not at correct position after export

Pointdump — Thu, 09 May 2024 15:52:10 GMT

Ya,
I don't know if you have anything usable. What part of your trench should be at the location in site_plan.txt?(ref lat: 47.3640, ref long: 8.3345) At what point in the trench linework is the rotation point?
"Trench (x,y,z):
6, 0, -1.3
-14, 3, -1.3"
is baffling. What does it mean?
Dave

Re: Georeference dxf in Civil3D not at correct position after export

ChicagoLooper — Thu, 09 May 2024 16:54:05 GMT

Hi @yhofmann7K3UB

You're over thinking how assign your modelspace coordinate system.

There's no special fancy-schmancy mouse-clicking and keyboard method to accurately assign your coordinate system. It's actually simple.

Do this.

Open a clean, brand new metric template. An OOTB generic template works best because there won't be any 'excess baggage' interfering with your drawing setup.
Use MAPCSASSIGN and assign your coordinate system. <<The MAPCSASSIGN is the most straightforward way to establish your CS. As long as you're not doing fancy-schmancy stuff like a custom CS with a special rotation or origin, or working with ground as opposed to grid, you'll be fine. Most users do NOT need to use sophisticated CS assignment methods to georeference their drawings. Use MAPCSASSIGN!!>>
On the Ribbon, Go to Geolocation Tab=>online Map Panel=>Change Map OFF to Bing Hybrid. The Bing logo will appear in lower right corner of modelspace and indicates you've successfully connected to the Bing Map server. Pan in until you see Bing imagery in modelspce. The imagery will be centered on a Red Geomarker (looks like a red bicycle wheel with red spokes.) You may have to zoom-out to 'find' Bing imagery (zoom way, waaay, waaaaaay out). Zoom in on the Red geomarker.
Zoom-in and use the labels in Bing Hybrid to navigate to your site. Draw linework for your map using Bing imagery as your guide. You may also COPY your line work from another drawing and PASTE your line work into this new drawing. Make sure you paste accurately directly on top of Bing imagery. You will need to (a) move your line work, (b) scale your line work, and (c) rotate your line work. (If you're lucky, you'll only need to move because your scale and rotation will be fine.)
Save this new drawing. You should consider deleting your old drawing so you, or someone in your office, doesn't accidentally use that bad drawing.

Re: Georeference dxf in Civil3D not at correct position after export

yhofmann7K3UB — Thu, 09 May 2024 16:53:12 GMT

so the origin of the local CRS should be at the given lat and lon (in EPSG:4326) and the heading is defined from east to the x axis of the local CRS.

The x,y,z are in the end/start of the trench in the middle at the bottom and the trench is 1.3m wide and 1.3m high.

I have attached a sketch of this situation

Re: Georeference dxf in Civil3D not at correct position after export

yhofmann7K3UB — Thu, 09 May 2024 16:53:19 GMT

so the origin of the local CRS should be at the given lat and lon (in EPSG:4326) and the heading is defined from east to the x axis of the local CRS.
The x,y,z are in the end/start of the trench in the middle at the bottom and the trench is 1.3m wide and 1.3m high.

I have attached a sketch of this situation

Re: Georeference dxf in Civil3D not at correct position after export

yhofmann7K3UB — Thu, 09 May 2024 16:54:25 GMT

so the origin of the local CRS should be at the given lat and lon (in EPSG:4326) and the heading is defined from east to the x axis of the local CRS.
The x,y,z are in the end/start of the trench in the middle at the bottom and the trench is 1.3m wide and 1.3m high.

I have attached a sketch of this situation

Re: Georeference dxf in Civil3D not at correct position after export

ChicagoLooper — Thu, 09 May 2024 17:19:04 GMT

@yhofmann7K3UB

Assign an appropriate coordinate system that has units of METERS. Use MAPCSASSIGN!!

Do not assign a coordinate system to your modelspace that uses degrees, if you do you'll have issues, big time! But you probably already know that.

Once you've successfully assigned a CS that's appropriate to your specific area on Earth, you'll get the Geolocation Tab on the Ribbon.

On the Ribbon go to Geolocation Tab=>Tools Panel=>Mark Position dropdown=>Lat-Long Icon (see image below).

Input your target Lat on the command line.
Input your target Long on the command line.
Click an 'empty area' in modelspace away from the icon to end the command. (You may input either DMS or decimal degrees, either is acceptable. If inputting DMS, use suffix D for degrees, suffix ' for minutes, and suffix " for seconds.)
The geomarker you've have just inserted will be geospatially accurate even though you've assigned a CS that uses meters. You can verify the geomarker's accuracy by selecting it and viewing its Lat/Long coordinates displayed on bottom of Properties Palette.
You can turn on on Bing Hybrid imagery to use as a basemap. The imagery can be compared against your inserted geomarker.

Re: Georeference dxf in Civil3D not at correct position after export

Pointdump — Thu, 09 May 2024 19:24:18 GMT

Ya,
I'm drawing a blank. Do you have any more information about the local CRS? Any other DXF's or shapefiles?
Dave

Re: Georeference dxf in Civil3D not at correct position after export

yhofmann7K3UB — Thu, 09 May 2024 20:04:02 GMT

Hi Dave,
Thanks. I also have the non-meshed .dxf as well as a screenshot of the drawing (however the z axis points in the wrong direction it)
Thanks
Yannic

Re: Georeference dxf in Civil3D not at correct position after export

Pointdump — Fri, 10 May 2024 17:00:50 GMT

Yannic,
Still thinking about this. I see what you did using the Transformation Tab. The problem with the Transformation Tab is the disconnect with Map Functions. My next thought was a custom projection. >>>EPSG:2056<<< in MAPCSLIBRARY has a "Swiss" projection. Really it's a Hotine_Oblique_Mercator_Azimuth_Center projection, and your rotation could maybe be specified in either the "azimuth" or "rectified_grid_angle". Experimentation is in order.
Dave

Re: Georeference dxf in Civil3D not at correct position after export

Pointdump — Sun, 12 May 2024 10:23:18 GMT

Yannic,
I think probably the easiest way is to Rotate, then Move Origin(0,0) to Lat:47.3640,Long:8.3345. Check whether those lats and longs belong to WGS84 or CH1903+ Datums, as there is quite a difference between the two.
Dave

Re: Georeference dxf in Civil3D not at correct position after export

Pointdump — Mon, 13 May 2024 06:47:56 GMT

Yannic,
I like how you set up the Transformation Tab. Probably the easiest way to get the trench linework into QGIS is to create COGO Points in C3D and export them as "Grid Easting" and "Grid Northing". Then in QGIS you can create linework connecting the points.
Dave