One of the techniques to produce 3D imagery data from UAV imagery is Structure from Motion (SfM). UNAVCO has put on a short course at the 2017 GSA Annual Meeting on the introduction of SfM for the Geosciences. The short course materials can be downloaded from this URL:
http://kb.unavco.org/kb/a...hort-course-864.html

Here is the description from the short course page:
High Resolution Topography and 3D Imaging II: Introduction to Structure from Motion (SfM) Photogrammetry

Structure from Motion (SfM), a photogrammetric technique that uses overlapping images to construct 3D surface models, is quickly emerging as a valuable research and education tool in geodesy, geomorphology, structural geology, and related disciplines. Images can be collected with a standard consumer-grade camera, making SfM a low-cost tool that compliments other 3D imaging technologies, such as terrestrial and airborne laser scanning (lidar). SfM can be collected from a hand-held camera or an airborne platform such as an aircraft, tethered balloon, kite, or UAS (unmanned aerial system), enabling 3D imaging of features ranging in size from decimeters to several kilometers. This one-day course will provide faculty, students, and professionals with an introduction to SfM technology, data collection and processing, and examples of science and educational applications. A combination of lectures and hands-on demonstrations of SfM equipment and data processing will be used.

The course materials appear to be a great introduction into SfM.