River mapping using digital imagery of unmanned aerial vechicle
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Date
2015
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Universiti Teknologi Malaysia
Abstract
The demand for aerial photogrammetry has increased especially after the development of unmanned aerial vehicle (UAV) system. This study explores the use of different types of UAV namely fixed-wing and multi-rotor as data collection platforms and utilizes UAV system for large-scale stream and river mapping. This study comprises of three experiments. The first experiment involved the mapping of a meandering flume. In the second experiment, it involved a real stream located in Universiti Teknologi Malaysia (UTM), Johor Bahru campus vicinity. The third experiment involved the mapping of river of one (1) kilometre (km) in length. Digital aerial images were acquired in the form of strips, which followed the procedure of acquiring conventional aerial photograph of 60% forward lap and 30% side lap. Ground Control Points (GCPs) and Check Points (CPs) were established using Global Positioning System (GPS) technique. The digital camera was calibrated using close range photogrammetric software and the camera calibration parameters were then used in the processing of digital aerial images. In order to process the digital aerial images, digital photogrammetric software was used for several processes such as aerial triangulation, stereo compilation, generation of digital elevation model (DEM) and generation of orthophoto. The whole processes were successfully performed and the output is in the form of orthophoto. The analyses of the photogrammetric results were performed based on different flying altitude and different GCP configurations. The results of this study showed that for large-scale stream mapping, the best result is orthophoto of 40 meter flying height. Finally, the best GCP configuration is 25 GCPs with the decimeter accuracy for all coordinates of real river study. In this study, it was found that, the Root Mean Square Error (RMSE) decreases when the number of GCP increases. Based on the finding of this study, UAV method is a unique alternative in comparison with the field measurement method, which is laborious and affected by operator efficiency. As a conclusion, UAV system has great potential for large-scale stream and river mapping or other diversified applications since it offers rapid data acquisition, low cost and produces accurate results
Description
Thesis (PhD. (Geomatics Engineering))
Keywords
Stream mapping, Aerial photography--Equipment and supplies, Drone aircraft, Drone aircraft in remote sensing