Thursday, February 6, 2014

Camera geometries for Structure-from-Motion mapping


Camera geometry, the way photographs overlap, is an important factor in successful mapping when using Structure-from-Motion (SfM). There are several main geometries that photosets fall into: divergent, convergent, parallel, and whether the camera is pointed at a nadir or oblique angles. The type of geometry you use is dependent on the research question and there is always going to be some natural variation in a photoset but you should attempt to keep a consistent overall geometry in the scene. These are simply guidelines, one of the beautiful things about SfM is that is can be forgiving, so if you do not take perfectly aligned photos your 3D model will not be lost. Also, I cannot stress the important of practice. Before you head out for a full field campaign find an analog to your study site and practice taking photographs using the different camera geometry guidelines. This will help you plan for the field and also let you experiment with the processing workflow and familiarize yourself with how the software behaves.