During my Master's studies at the university, I developed a UAV landing system for quadcopters. This feature allows self-landing of your drone on a special symbol on the ground. It means that drone can catch the target via its optical vision system and then slowly go down until its full landing on the symbol.
As the results of this project, a test drone was programmed to fly to a defined place via GPS navigation, where it recognized a prepared symbol "H" on the ground. Then, the drone did self-landing on that symbol with 93% accuracy.