Using a drone and photogrammetry software to create orthomosaic images and 3D models of aircraft accident sites

Drone technology has developed significantly in recent years. Lightweight quadcopter drones with quality cameras are now very affordable. The UK AAIB has been operating drones at aircraft accident sites for over 2 years and has used them at 23 different accident sites varying from fields to major airports. This paper presents some examples of images obtained by AAIB-owned drones that would have been difficult to obtain by other means, such as the tops of broken trees and wreckage below a cliff in poor weather. It is less expensive to use a drone for accident site aerial imagery than a helicopter and the images can be obtained quickly, within minutes of arriving at an accident site. This paper also presents how photogrammetry software can be used to process drone images to create geo-referenced maps, orthomosaic images, and 3D visualisations of an accident site. This is a new technique and the AAIB has used such software to create 3D ‘point-cloud’ models and orthomosaic images of two large accident sites. The photogrammetry software enables measurements of a site to be taken that can be up to 1 cm accuracy using drone imagery alone. This paper presents some of the lessons the AAIB has learnt from using this software, and presents some examples of measurement accuracy from accident sites and from separate trials. The combination of drone imagery and photogrammetry software provides a very useful new tool and link in accident site documentation and analysis, and at a much lower cost than hiring a commercial helicopter or using laser scanning equipment.