Making Digital Elevations Models (DEM) on the cheap

It is a little off topic but I thought many of the forum goers might find the Photosynth to 3D process I've been working on useful for creating 3D models from aerial photos.  The process is pretty simple and FREE:

·         Gather images with a lot of overlap (like most of our aerial shots)

·         Upload the files to http://www.photosynth.net (or use the open source Bundler app http://phototour.cs.washington.edu/bundler/ )

·         Use this exporter to extract the point cloud http://pspcexporter.codeplex.com/

·         Use a product like Meshlab  http://www.meshlab.net/ (hard to get good results) or VrMesh Studio ( http://www.vrmesh.com/products/overview.asp  ) to generate a mesh surface from the point cloud.

 

Here are two examples from my work in Ecuador and West Texas:

https://www.youtube.com/user/mdwillis01#p/a/u/0/2-oK5lnNA-I

and

https://www.youtube.com/user/mdwillis01#p/u/6/nJgvLll57f0 (only part of this one was done with Photoysnth).

The images were captured from kite and balloon platforms but the same workflow should work for any series of photographs.

Also, here is a Google Earth file with some of the same data http://70.114.146.89/~mwillis/Puchara_Grande.kmz (~10 Mb).  My linux box connection is slow. It'll take a bit to download.

-Mark

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Replies

  • Thanks for the sharing. Good info :-D

  • Hello, I also am an enthusiast of kite mapping, and not only. Unfortunately I struggle by doing it on my own. I have tried out, and keep using airplane and multicopter drones and kites with rigs. I also tried to recrute a friend of mine in developing o personal version of bundler, in a sense. I would like him to accomplish all that I need, him being the programmer. Try to put it all together in some sort of an app to run under fedora or ubuntu that should include georeferencing of point cloud after generating, stitching of images, orthorectification. meanwhile, I still am on my own and have to give him examples and data. So I kinda gathered some open source apps for generating the point cloud, the georeference it using a bit of script. Stitching I manage to do with ICE. But I have pb with this since it is open source and underdeveloped, it crashes frequently, or it limits the amount of data that can process. So I was wondering, what do you use for georeferencing the pointcloud and how do you drape the image stitch upon the 3D model and orthorectificate it?

  • I realize there has not been a lot of activity on this forum post for a while, but I would like to share some research with you regarding the attainable accuracies of Mark's Photosynth workflow. Please refer to a presentation I have given at a GIS conference

  • Hello to all of you!

    Great job Mark! I want to ask a question.

    I' m interested in making DEM and orthophotos with a small RC plane on the cheap. I will use it for morphotectonic studies, coastal and wetland monitoring.

     

    I want to use a cheap rc plane and mount a pocket camera in order to take nadir photos. Any suggestions?

     

     

    A great free (open source) software for orthorectification is ILWIS. You can download it from 52 North site. ILWIS is a windows program, with a great gui and an extensive help file.

    GRASS GIS is one of the best software for ortho but you it has a very steep learning curve especially for hobbyists.

    @Bohumil Michalik: ERDAS is also a very powerfull but quite expensive software.

  • Hi Mark,
     
    Many thanks your great works of using kite for aerial survey and archaeology.  I am also want to apply this technique to preserve the old military sites, relics and bunkers of World War II.  I am able to take aerial photos by UAV and convert the photos to point cloud by Photosynth.  But I am not sure how to convert the point cloud file to a mesh model like what you do in "Photosynth to 3D conversion".  Could you enlighten me which format of point cloud is required and how to convert this file to a mesh simply?  Many thanks!
  • @Francisco,
    I agree, this is not as simple as one should hope. I do however think there are signs of light in the tunnels. E.g. the GRASS GIS community is working on a new version of GRASS, which will hopefully make what I belive is the RolsRoyce of open source GIS and Photogrammetry software more easily awailable, also for non-experts. See: http://grass.osgeo.org/grass70/index.php

    And while we are waiting for more new software and tutorials to show up, here is something fun to play with: http://www.hypr3d.com/
  • I just found a reference to the software AirPhoto: http://www.uni-koeln.de/~al001/airphoto.html First impression is that this package looks very promising. Anyone who have knowledge of the software?
    The Bonn Archaeological Software Package - AirPhoto
    A program package for archaeological aerial photography and mapping, with extensive graphic display on scanned backgrounds
  • Dammit Gary you beat me to it! Well done!

    I wish I only had a part-time job like you....

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  • Gary, nice job. Have you managed to make an orthophoto of the site? That still remains a challenge to do for free without impinging on copyright issues! This is an interesting exercise but at the end of the day for serious business and if your time is expensive enough its probably better to just buy a proprietary package - the prices are coming down relative to what they can do - albeit slowly.
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