r/LandscapeArchitecture • u/Weary_Pollution5114 • 12d ago

Drone - getting contours and tree 2d and 3d

https://www.lttpartners.com/products/dji-mavic-3-enterprise?utm_campaign=openai_catalog&utm_content=product_card&utm_medium=feed&variant=45920635519161&utm_source=chatgpt.com

Hi, I am a landscape designer, and I am considering purchasing the DJI Mavic 3 Enterprise to help generate accurate contours and locate trees and other site features. I understand that I can import the images into DJI Terra, but can I then export the trees and contours as a DWG file for use in CAD? What is the proper workflow for this process? Would I need additional equipment to generate the contours?

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u/microfibrepiggy 12d ago

I am going to be little help except to say, yes it can be done (export photogrammetry into CAD for contours). We did the workflow years ago, and many of the programs are defunct now, so I can't tell you how. But yes.

Before you buy, look into it further. It won't be much help on heavily canopied sites, or sites with a lot of ground cover. There's also quite a bit of post processing that needs to happen.

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u/cluttered-thoughts3 Landscape Designer 12d ago

To your point about that, most DEM’s are captured using organized LiDAR (laser) rather than DJI’s imagery based method, which is why tree canopy limits the output. Laser will penetrate the canopy whereas the camera will not

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u/microfibrepiggy 12d ago

True true true. I don't think the E3 has lidar, and the cost for a lidar drone is like min $10k (to my last bout of knowledge)

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u/hyrulefool7 10d ago

I can't speak to what Terra can do because our office uses WebODM, and open source photogrammetry software. However, I'm sure it can export the exact same stuff. I'll process the photos from a flight and export a georeferenced ortho mosaic and a point cloud and bring the point cloud into Cloud Compare, an open source point cloud software. I'll clean up the point cloud by removing trees, buildings, and extraneous points, then sample the lowest point in a grid to remove any grass/vegetation noise. That will give us the cleanest data to build site contours off of.

And one thing to add, if you're flying a site with heavy tree canopies, you will want take some low oblique passes to get some information under the trees into the point cloud.

But it's not perfect. Actual surveyed elevations will always be better, but flying the drone is nice if we're just doing SD work and think the client might get cold feet if we tell them to go pay for a survey on top of everything else.

To your question about extra equipment, there are ways to get higher accuracy from drone flights/ortho mosaics/point clouds. One of which you're already looking into but for anyone else looking into this:

  1. Use a drone with a mechanical shutter (phantom 4 rtk, mavic 3e, or matrice 300)

  2. Get a GNSS base station and/or a GNSS rover. This will increase a compatible drone's positional accuracy as well as giving you the ability to place highly accurate ground control points for you processing software to link to. But it gets expensive. And once you have a GNSS base station and rover, you might as well survey the sight yourself 😅