DXF Contour Export Issues

Something changed recently with the contour DXF export where when I bring it into Civil 3D (tested '21 and '22 C3D) via CLASSICIMPORT it only imports roughly 60% of the contour data and it does not seem to be the same 60% if I repeat the process. Trying to determine if this is a DD issue or a C3D issue and wondering if anyone else is having similar issues recently. It seems like the format of the DXF may have changed which is causing issues on import but I’ve been waiting on DD to respond and have a client anxious to receive their contour data. Any help would be greatly appreciated.

FWIW - I’ve tried both DTM and Elevation exports and get similar results.


Our C3D nor Carlson Civil are having any issues so far. Are you working in the downloaded DXF or XREF’ing it into another drawing? Looks like 1ft DSM contours?

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We are inserting the downloaded DXF file. When inserted the first time in a new C3d drawing, i’m prompted with the “Redefine Block” pop up as if i have already inserted the block before. We’ve tested 3 PCs so far and have found the same results. I inserted a previous DXF DroneDeploy Export from 4/30/22 and it inserts as expected, without the “redefine block” prompt. If we do redefine the block, it inserts/leaves out different portions of the data each time.

Michael - I’ll email you the new export and old export if you have time to test.


Is there a reason you are importing it instead of just opening it?

I might be missing more than you were if it’s the same as shown above. This is what I see in Carlson with IntelliCAD. I forgot I reset my computer a couple months ago and reinstalled without C3D but I sent it to my C3D guy and will let you know what he sees.

I just realized what you meant by insert… since you can’t XREF DXF’s. Have you tried to open it straight out and save it a a DWG first?

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I have not, that is a good idea. Ultimately I want the contours in the working file, not an XREF but the save as a DWG along with copy with basepoint could work. Still curious what changed but that is solid work around.

EDIT: Tried opening as a DXF and saving as a DWG - no problem. When I try to XREF the DWG into a new blank drawing i get “ERROR: UNABLE TO LOAD”. Also tried copy w/basepoint from the DWG and again get an error. I had to re-open the contour DWG, run an audit, fix the error, and then it worked as expected. I would assume the error that it fixed is what is causing all of the issues.

EDIT 2 - Audit Text

Validating objects in the handle table.
Valid objects 4732 Invalid objects 0
Validating objects completed.
Reading handle E object type AcDbDictionaryWithDefault
Error 13 (eUnknownHandle) Object discarded
Creating new ACAD_PLOTSTYLENAME dictionary
Salvaged database from drawing.
Auditing Header
Auditing Tables
Auditing Entities Pass 1
Pass 1 4700 objects audited
Auditing Entities Pass 2
Pass 2 4700 objects audited
Auditing Blocks
0 Blocks audited
Auditing AcDsRecords
Total errors found 1 fixed 1
Erased 1 objects
Opening an AutoCAD 2018 format file.
Regenerating model.
**** System Variable Changed ****
1 of the monitored system variables has changed from the preferred value. Use SYSVARMONITOR command to view changes.

Typical autodesk style. Fixed one error and no real information on what that error was, lol. Haven’t heard back from my C3D guy yet on the classicimport but will update later. I think some of the reason why we haven’t seen this is because when we bring DTM contours in and save it as a DWG it is the file of record and we are bringing other content in as we want to see it. Part of the reason for this is that we try to leave files as close to their original condition as possible and if we need to change things for something like this to work then we have a complete copy of the original. It’s just something I’ve learned over the years and how quickly this data piles up that we don’t necessarily need every single file. As a matter of fact, when we do BIM, the file that is loaded into the model is always named the same, so it automatically updates throughout everything.

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Agree on the file management front. If it’s purely record data, we do the same. Where we run into these issues is on the analytical side, when we need to run a volume analysis for example and need the contour data to generate & compare surfaces outside of DD.

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