Monocular image-based time to collision and closest point of approach estimation

This paper deals with monocular image-based time-to-collision (TTC) and closest point of approach (CPA) estimation for aircraft sense and avoid. First, it proposes a disc-based pinhole camera projection model which can better represent a real 3D object. Then it proposes simple least squares optimal line fitting-based techniques for TTC and CPA estimation based-on measurable image parameters only. Possible errors in the image are considered through design nomograms and a collision decision threshold selection technique is presented. Theoretical results are verified through software-in-the-loop simulation and real flight test results. To the best of the author's knowledge the disc-based projection model and the line fit-based TTC and CPA estimation are new contributions in this field.