UAV PHOTOGRAMMETRY: BLOCK TRIANGULATION COMPARISONS

UAVs systems represent a flexible technology able to collect a big amount of high resolution information, both for metric and interpretation uses. In the frame of experimental tests carried out at Dept. ICA of Politecnico di Milano to validate vector-sensor systems and to assess the UAVs images' metric accuracies, a block of photos taken by a fixed wing system is triangulated by several software. The test field is a rural area included in an Italian Park (Parco Adda Nord), useful to study flight and imagery performances, on buildings, roads, cultivated and uncultivated vegetation. The UAV Sensefly, equipped with a camera Canon Ixus 220HS, flew autonomously over the area at a height of 130m yielding a block of 49 images divided in 5 strips. Sixteen pre-signalized Ground Control Points surveyed in the area through GPS (NRTK survey) allow the referencing of the block and accuracy analyses. Approximate values for exterior orientation parameters (positions and attitudes) were recorded by the flight control system. The block was processed with several software: Esdas-LPS, EyeDEA (Univ.of Parma), Agisoft Photoscan, PIX4UAV, in assisted or automatic way. Results comparisons are given in terms of differences among digital surface models, differences in orientation parameters and accuracies, when available. Moreover, image and ground point coordinates obtained by the different software are independently used as initial values in a comparative adjustment made by scientific in-house software which can apply different constraints to evaluate the effectiveness of different methods of point extraction and accuracies on ground check points