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I have two point clouds obtained via structure from motion (ground photos of sand-dunes + Visual SfM/Agisoft Photoscan).

If I wanted to generate a DEM from these point clouds and difference them to look at elevation/sediment change, how would I go about doing this?

Is there any free software that can achieve this easily? I am a beginner at using GIS software.

At the moment I am using the free trial of Agisoft Photoscan, which can export the point cloud in Wavefront OBJ, Stanford PLY, XYZ text file, U3D, ASPRS LAS, and PDF formats.

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    In which file format are your point clouds stored? (Please include this as an edit to your question rather than a comment) – Martin Oct 26 '15 at 11:42
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    This is a half answer so I'm not going to post it as one: Since it's sand dunes it's mostly a 2 dimensional problem. Convert both to rasters (might need some clean up), and subtract one from the other. Look into QGIS as a free option. – Wes Oct 26 '15 at 12:04
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    I think that liblas could do the trick liblas.org – radouxju Oct 26 '15 at 12:44
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    Can I do both the conversions and raster subtraction in QGIS? – ddddDDDD Oct 26 '15 at 15:12
  • fusion is pretty easy to use from the command line. i find their gui confusing. you can go from las to dtm(GridSurfaceCreate) and from dtm to tiff(DTM2TIF) with fusion (keep your coordinate systems and resolution in mind as you go though). Then you can open up the tiffs in QGIS and subtract them from each other with the raster calculator creating a raster that shows differences in your units +/- – gomapping Dec 6 '16 at 21:52
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You want to generate DEMs from point clouds, and then, compare such DEMs.

The following posts have examples using free software:

  1. Generating DEMs from point clouds:

  1. Comparison of DEMs:

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You can try the free trial of LiDAR360 (LiDAR360 online user guide), which can import the point cloud in LAS, LAZ, PLY, TXT, XYZ etc.

To generate DEM from point clouds:

  1. Remove the outlier points (Data Management > Point Cloud Tools > Outlier Removal);

  2. Classify Ground Points (Classify > Classify Ground Points);

  3. Generate DEM (Terrain > DEM);

  4. Compare the differences between two DEM files (Data Management > Raster Tools > Band Calculator).

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