[H-TT14] HIGH-DEFINITION TOPOGRAPHIC DATA FOR CONNECTIVITY IN THE ANTHROPOCENE

[HTT14-01] Comparison of topographic outputs obtained through Nadir and Oblique UAV camera axisComparison of topographic outputs obtained through Nadir and Oblique UAV camera axis

*Anuar Ahmad¹, Muhammad Hamid - Chaudry², Qudsia - Gulzar² (1.Universiti Teknokogi Malaysia, Johor Bahru, Johor, Malaysia, 2.Univerity of Punjab, Lahore, Pakistan)

Keywords:Oblique Aerial photos, Nadir Aerial Photos,, DTM, DSM, Topography

High spatial resolution of three dimensional modelling of earth surface represented by digital surface model (DSM) presents multiple challenges to earth scientists especially in the surveying domain where slopes and angles of topography are varied. Unmanned Aerial Vehicles (UAV) is a fast growing technology for high spatial resolution DSM generation of small areas. UAV flight planning parameters determine the quality and utility (potential) of UAV photogrammetric products. This research compares and identifies the potential of oblique camera versus nadir camera parameters in UAV surveying for dense urban areas with tall structures and varied angles. UAV images captured through off-nadir camera axis can capture more details of sides and bases of tall structures which are generally obscured in nadir axis images. Two photogrammetric projects are processed with camera axis at nadir (-90°) and off-nadir (± 35°). For photogrammetric project with nadir camera axis, images are captured with DJI Phantom 4 Advanced from 100 meters flight height with 20 megapixel camera resolution. Photogrammetric projects with off nadir camera axis are captured with RIEGL RiCOPTER platform from 130 meters flight height with Sony Alpha 6000 24 megapixel cameras. Images of two photogrammetric projects were processed using SfM techniques in Pix4D software to calibrate images automatically based upon EXIF information for tie point’s generation. Then calibrated images were georeferenced by using GCPs to have a dense 3D point cloud. From this 3D dense point cloud a mesh is generated to produce orthomosaic, DTM and DSM. For image processing and accuracy, assessment 8 Ground Control Points (GCPs) and 10 Check Points (CPs) are acquired through Global Navigation Satellite System (GNSS) geodetic survey grade receiver. Two projects are compared for geometric accuracy, data acquisition and processing time, disk space requirements and potential for topographic variants. The accuracy of both the projects meet the requirements. The study establishes optimal standards of topographic surveying for camera axis determination for UAV images acquisition in heterogeneous areas especially comprising of multiple slope types and angles.