Getting rid of vegetation for contour lines

Hello all,

I have a quick question that can hopefully be answered in regards to surveying, and more specifically in regards to generating contour lines for civil engineering purposes. I have mapped a 220 acre section of undeveloped land that is getting ready for development.

The map came out great and I was able to generate the contour lines, the only issue is that there is an abundance of sage brush that was also included in my contour lines.

As you can see above, the lines are super messy and are not what a client would usually expect. My question is, what is the best/most effective way to go about getting rid of these extra lines? Is there other software I need? Do I need to adjust my settings and rerun the mapping process?

Thanks in advance, any tips or advice are certainly appreciated.

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Was that the DTM contours? If not, try that. Either way the filtering in the DroneDeploy DTM hasn’t gotten us the data we need so we use Carlson Precision 3D Topo to create a more controllable DTM directly from the point cloud. It also allows you to save the points you are filtering so that they can be used later to create different surfaces.
Another trick is to delete the smaller contour lines while maintaining any breaklines and you will get a smoother bare earth model. We can often do this by recreating the contours through different methods and removing (not redrawing) any contour lines that are less than a certain length so that you don’t end up with all the little artifacts.

Yes, those are the DTM lines. I attempted the DSM and DTM contours and the results were very similar.

As far as using DroneDeploy, would using more GCP's help this issue at all? Or do you recommend Carlson for all projects of this nature? And in regards to Carlson, which package would you recommend to buy? I am looking at their website and there are a few different package options.

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If you are looking at a Civil heavy workload with a little survey and particularly using point clouds then I think Carlson Precision 3D Topo and Carlson Civil (or Survey) is about as good of a workflow as you are going to get. We output to machine control as well so it really does the job for us. Civil 3D (too tedious) and Bentley (to proprietary) have their strong points, but in my opinion are not for survey and mapping with a drone should carry the same principles.

Carlson’s philosophy on making big changes is pretty safe so you would be ok without maintenance and running it for a couple of years with Civil if you chose to do so. Precision 3D Topo has had some pretty good advancements lately and seems that it will be good for the near future, but drone use is radically developing so who knows what will happen in a year.

The next step with Civil is to put it on top of AutoCAD which does make it a little more powerful so if you already have it all the better. If not then the native IntelliCAD is adequate for pretty deep tasks. I have been in AutoCAD for a long time, but after forcing myself to try IC just to check it out it did what we needed. Last but not least, this surface and analysis tools are by far better than any other CAD.

Thanks for the quick reply Michael, your expertise is appreciated. I have installed Carlson 3D Topo along with Carlson Civil + iCAD. I have successfully smoothed out the contour lines that I originally posted above, see picture below.

This is exactly what I have been trying to do, however I have ran into an issue when exporting to DXF. I'll continue to research on my side of course, but I was curious if you had any tips or tricks when doing this. Below are pictures of the result of exporting the above to a DXF. One is the full picture, the other is zoomed in. I cannot get rid of these poly lines.

Those are the triangles of the surface. Did you bring in the point cloud or make the surface from the contours?

I prefer to save the surface as a TIN and draw the contours in Civil. Also, that will allow you to run some of the surface routines in the menu I previously shared and compare surfaces against each other. Make sure you save your scene as a P3D file as well. I like to save it once as soon as I get everything imported and setup before I start editing. Then again as a different file once I think I am done. Just for convenience if I need it for different purposes.

Gotchya, I imported the pointcloud from a .las file. I then filtered the points to get rid of the vegetation and just smooth the ground out in general. After this, I created a surface from the points and was able to get smooth contours with the new surface.

I was able to get the DXF files that I needed for this job just by using Topo 3D. But I am interested in using Civil to draw the lines as well. Do you have any good resources for someone who is learning Carlson? I see that there are webinars, but the only ones that seem relevant to what I am doing are all in January. Either way, I'll definitely be using this a lot. Thank's a million for your time and expertise, you've helped a ton!

My pleasure, always happy to share. Sounds like you got a good chunk of it figured out! The art is learning to manipulate the Bare Ground and Outlier setting sin different scenarios. One tip to help with cleanup is to use the Planar Elevation Snap. When trying to cut out items manually by polylines it can be difficult to snap directly to points as you trace around. It is easier if you have a surface that will let you click anywhere, but then you have to deal with creating and deleting repeatedly. The Planar Snap let’s you set the elevation of the area that you are working in and just click vertices without point snapping or creating surfaces.


Once you click Draw Polyline you can hover over the points and get a close elevation to enter. I like to use the toe of the pile of object that I am extracting as the points under the elevation you choose will darken and it makes it easy to see what to take out. I use this when filtering keeps destroying slopes or breaklines.

Working with surfaces in Civil is something you’ll pickup as you go. It just makes it allot easier than dealing with entities onscreen especially from several different files. You can quick-draw surfaces and contours just to see what is going on. All the drawings really contain then are your calc boundaries and analysis output like cut/fill color maps, volume calcs and etc.

Contour from TIN…

…brings up the same menu to draw contours as any other related command. I like these settings. You can draw Index Contours if you like here as well. Labels tab right next to it.

They have a good amount of videos on there site and mostly the same on YouTube, but you can also find other user’s tips. I personally like the Help menu as it is easy to search and find pretty much any command without waiting for a video to get there.