My work on this has involved two data sets:
|Ship models from the 18th century in the collections of the US Naval
Ship model, including the stand, colored by elevation.
|Ship model with the stand largely removed.
If you need to recolor the bottom of the images to remove background that you do not want in the 3D model, use the MICRODEM image editor. This will preserve the EXIF tags in the JPEG files which the SfM software wants. Do not change the size of the photos.
|Photos of the geology of Deadman Canyon, in the Sheep Range of southern Nevada.|
Suggestions culled from the web, mainly applicable to Photosynth (no longer available), but probably apply to other software as well:
All of this software has crashed; you might need to get the commercial program (it has a demo version, and a reasonable academic license), or experiment to find out if the problem is the software, you not following directions, or badly configured imagery.
One of the challenges is that the computer science and computer vision communites has a different axis convention (the z axis comes out of the page or screen), while the GIS convention has the z axis vertical, normal to the earth's surface. You must insure that you understand the difference, and keep your coordinate systems straight.
Online download at http://ccwu.me/vsfm/
Agisoft Photoscan is the commerial standard. I had a student use it. We got better results with the free software, but that could have been because we learned from the issues with the photos to optimize the geometry, and we used a commercial DLSR instead of a smart phone.
Options I have not tried, but have good reviews:
Might need to check on the axes, which are not the GIS x-y horizontal and z vertical:
SfM Georeferencing: http://www.lancaster.ac.uk/staff/jamesm/software/sfm_georef.htm which I have not yet tried.
last revision 1/4/2018