Official comment

here are not technical papers that have been published for our particular algorithms. Pretty much all of the different softwares that are available for 3D model based orthophoto generation and 3D model reconstruction are doing the same thing. Our methods are proprietary and were developed over 15 years of doing military and commercial mapping work so there was no impetus to publish. Our techniques are probably most like those utilized by Pix4D and they seem to have a lot of documentation on the topic.
https://support.pix4d.com/hc/en-us/sections/200591029-Scientific-White-Papers-and-Presentations