DTM Accuracy Comparison Between Onboard RTK GNSS UAV versus Low Cost Quadcopter UAV at Different Geomorphological Sites: A Malaysian Approach

Shu, Ji Linn (2018) DTM Accuracy Comparison Between Onboard RTK GNSS UAV versus Low Cost Quadcopter UAV at Different Geomorphological Sites: A Malaysian Approach. [USQ Project]


Unmanned Aerial Vehicles (UAV) refers to the unmanned aircraft, including the fixed wing, multirotor and airship, etc. UAVs are used by professionals such as surveyors, contractors, engineers to collect spatial data through a camera which is capable of capturing high resolution images mounted on the UAV. The images are then ortho-rectified to obtain output such as digital elevation models (DEMs), digital terrain models (DTMs) and digital surface models (DSMs). These are valuable spatial data which can be used for project development planning and with integration with Geographic Information Systems (GIS). Currently, most of the surveying jobs done in Malaysia are still using the terrestrial methods which is total station and global navigation satellite system (GNSS). Most of the surveyors from small to medium size surveying firm are reluctant to venture into aerial photogrammetry due to the misconception of excessive cost to purchase Unmanned Aerial Vehicles, Cameras and complex Image processing software. The surveyors were also uncertain about the true accuracy of UAV photogrammetry because most companies do not provide any guarantee on its accuracy. On the other hand, Total stations and GNSS are classified by the local authorities as the legal surveying instrument to define cadastral boundaries. Therefore, surveyors feel more comfortable and confident in utilizing the terrestrial method.

To fill in the gap of the current situation, this paper aims to determine the optimum flight configuration for low cost multirotor to obtain the most accurate DEM results. This report will look at using one of the most affordable UAVs model in the market which is DJI Mavic Pro with price of AUD$1000 only and compared to the higher cost On-board RTK GNSS Fixed Wing UAV – Sirius Pro. DJI Mavic Pro is built in with a 12.7 Mega Pixel gimbal camera with 3 axis rotations which fulfils the basic requirement for aerial photogrammetry. The flying platform, imaging sensor system and data processing software will be discussed in this paper. Pix4D capture is a free app which is compatible with DJI Mavic Pro model will used for pre-flight planning of the above-mentioned UAV photogrammetry. On the other hand, Sirius Pro is equipped with a RTK-GNSS enabled dual frequency receivers which promise an absolute block orientation with high accuracy. Sirius Pro is able to capture georeferenced images which gives the advantages of using lesser number of ground control point. Pix4D software is chosen as the most effective and user-friendly photogrammetry software to process the images capture to create professional ortho-mosaics, point clouds and 3D models. Pix4D is very advanced in automatic image extraction and artificial aided addition of the tie points for images with large tilt angles. The time and cost efficiencies during image acquisition and processing using UAV photogrammetry will be compared to the terrestrial method.

For this experiment, three cases will be carried out considering different terrain morphologies such as overgrown, dense vegetation and foliage area and tall buildings etc. Each case will be tested at flight altitudes of 60m and three different numbers of Ground Control Points (i.e., 5, 10, 15). This report focuses on the advantage of low altitude aerial photogrammetry to produce a high spatial resolution stereo image. The least cruising speed, camera configuration, and the quality of the Inertial Measurement Unit are limitation factors controlled throughout the experiment to obtain the optimum results. Combine image acquisition mode such as double grid mission and point of interest mode will be carry out during the test to discover its impact on positional accuracy. The root-mean-square error (RMSE) will be used as a measure to assess the accuracy of the DSM (Z component) and orthophotos (X, Y, and XY components). The ultimate goal of this research is to achieve an accurate Digital Orthophotos which can meet the Malaysian standard mapping requirement of 1:1000.

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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Spatial Science (Honours) (Surveying)
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 - 31 Dec 2021)
Supervisors: Chong, Albert; Apan, Armando
Date Deposited: 05 Sep 2022 23:56
Last Modified: 05 Sep 2022 23:56
Uncontrolled Keywords: Unmanned Aerial Vehicles (UAV); surveying
URI: https://sear.unisq.edu.au/id/eprint/40777

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