Vertical Accuracy of Digital Elevation Models from Three UAS Platforms and Georeferencing Methods

Authors: Marissa Keck*, Utah Valley University, Jeremy Saldivar*, Utah Valley University
Topics: Spatial Analysis & Modeling, Field Methods, Cartography
Keywords: unmanned aerial systems, digital elevation models, structure-from-motion, geospatial surveying
Session Type: Poster
Day: 4/13/2018
Start / End Time: 1:20 PM / 3:00 PM
Room: Napoleon Foyer/Common St. Corridor, Sheraton, 3rd Floor
Presentation File: No File Uploaded

We compared the accuracies of digital elevation models (DEMs) produced with structure-from-motion photogrammetry using different cameras, unmanned aerial system (UAS) platforms, and georeferencing techniques. The UASs and cameras were a Phantom 4-Pro quadcopter (stock DJI 20Mpixel camera), eBee Plus fixed-wing (20Mpixel SODA camera), and DJI Matrice 100 quadcopter (24.3Mpixel Sony A6000). The Matrice 100 and eBee Plus carried on-board carrier-phase GNSS systems that measured camera positions using post-processed kinetic (PPK) solutions. Point clouds were constructed from photographs taken with each platform at both Rush Valley, Utah, and Dry Lake Valley, California, using ground control points (GCPs) for georeferencing. In addition, point clouds for both sites were made from Matrice and eBee photos using only photo geotags, and using geotags plus GCPs for georeferencing. Point clouds used 1,227 to 3,560 photographs, contained 463,752,119 to 1,327,879,287 points, and covered 0.72 to 3.10 km2. DEMs were created from each point cloud using Agisoft’s built-in binning method, and vertical accuracy was assessed by calculating root-mean-square-error (RMSe) for each DEM relative to bareground checkpoints measured using PPK GNSS. RMSe for the Phantom georeferenced with GCPs only averaged 12.4cm. DEMs georeferenced with camera geotags only averaged 11.9cm higher than checkpoints for the eBee, and 19.0cm for the Matrice, indicating an elevation bias in point clouds and DEMs georeferenced with this method. After removal of the bias, RMSe were as follows: eBee camera geotags only, 4.6cm; eBee camera geotags plus GCPs, 4.9cm; Matrice GCPs only, 6.2cm; Matrice camera geotags only, 5.0cm; Matrice camera geotags plus GCPs, 5.4cm.

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