Any suggestions for trouble shooting this issue? Both Civil 3D and my Pix4D model are using the exact same coordinate system, units etc… I have uploaded an image with my processing and survey settings. This is the process I follow. I process Calibration, then Dense Point Cloud then DSM, Orthomosaic and Mesh all at once. Once that is complete I create the contour lines using teh following:
Terrain Classification, Grid of Points, TIN, DTM, Contour lines.
I then go to file, export, contour lines, zip shp. Then I extract the zip file. I open Civil 3D. Perform the MAPIMPORT command to bring in the contour poylines and choose the SHP file.
My spot elevations on my surface in Civil 3D created from the contour lines is 6 to 15 feet off compared to the pix4d Matic Model whose values are more accurate tor real world values.
Any help is appreciated.
Thank You.
Processing and Survery Settings.pdf (139.0 KB)
Creating a surface from contours gives me the icks, using the parlance of the youth.
You didnt provide enough information to know what’s occurring, though. Check the elevation of your contour-derived civil3d surface directly on top of a contour vertex. I assume that surface check aligns with your contour elevation it was made from, correct? Does that also align with the elevation in your pix4d point cloud, at the same spot?
If so, you’re seeing the result of interpolation when making a TIN from contour lines. Siif thats what is actually happening, you’re just using the wrong export from matic.
In matic, you have a 3d point cloud. Since you generated contours from it, I assume you ran ground classification first. The ground classified point cloud is what you want to import to civil 3d and make a surface from it. If the point cloud is too dense for you to manage, model keypoint extraction / intelligent point thinning / low pass filter at an appropriate spacing are all options that will help reduce surface complexity without running into massive errors resulting from interpolation between contour lines.
…or I’m totally missing the mark it’s a datum or unit issue as you move between software. Either way, it would be helpful to provide more info like your quality report, survey points, etc.
Edit: sorry, I skimmed past your comments on the first reply. You’re already making a TIN. Can’t you export that to a LandXML and just bring that into civil3d?
Recreating surfaces from contours (that were already made from a TIN surface) is very possibly creating the error your seeing. 6-15ft would be a huge interpolation error, but that also just depends on the contour interval you made, the relief across the site and how localized that anomaly is (and if you were filtering out closed contour generation below a certain threshold).