[gene-h]

Well a much better way to do optical guidance would be to do what some cruise missiles do, look at the ground below and find the most similar image in a big database of aerial photographs. The insane thing about this approach is that it was done in the 50s![0]

Another approach would be to do what insects do and use optical flow. Essentially look at how fast the ground is moving to figure how fast the UAS is moving and integrate to figure out where you are. This is exactly how optical mice work, in fact optical mice sensors have even been used to do this. Below is an example of a quadcopter that employs such system.[2]

[0] https://en.wikipedia.org/wiki/TERCOM [1] https://en.wikipedia.org/wiki/Optical_flow [2] https://www.youtube.com/watch?v=bbS1N--bT0w