Evaluation of DTM Accuracy Based on Different Flying Heights of UAV on a Uniform Surface

Wickramasinghe, Manod (2017) Evaluation of DTM Accuracy Based on Different Flying Heights of UAV on a Uniform Surface. [USQ Project]

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The combination of UAV and aerial photogrammetry has become important aspect of modern industries in engineering and surveying. Application of aerial photogrammetry in engineering and spatial science brings a number of benefits. Calculation of volume and area of spoil heaps and/or excavations can be done by processing digital photographs. Nowadays, effectiveness and efficiency has become one of the most important aspects of the business. Therefore, it is critical to find most constructive way to undertake a step of a project. The flying height of an UAV has a considerable influence on the quality of the aerial images which will be finally impact on the quality and accuracy of the DTM generated by particular aerial photographs. With changes of flying heights, it directly effect on scale of image and ground resolution of the image. There is an area with minimum studies related to UAV flying height, usage of ground control points and its effectiveness on final outcome.

Undertaking study in a uniform ground surface will control the influence of other factors such buildings, water bodies and vegetation on final DTM creation. The UAV flying was undertaken over the ground surface with different restricted height intervals of 60m, 90m and 120m. As a control, the conventional surveying with total station was undertaken. The all ground control points were included in both surveys. The field UAV and conventional data were processed using Pix4Dmapper and terramodel software respectively. The final DTM processed by UAV images was compared DTM developed by other method to assess accuracy of UAV method.

In the asphalt car park area and grassy playground area, the contour lines generated with DTM of 60m data shows 20mm accuracy compared to conventional survey. The contours generated with DTM of 120m data shows average accuracy of 40mm. The contours generated with DTM of 90m data shows the accuracy of 30mm data which indicate with change of the flying height results tend to change. At lower altitude results shows greater accuracy compared to results of the higher accuracy. The DSM generated by Pix4D was distorted due to long grass around gravel driveway which changed to 100mm accuracy.

The study of RMSE for surface of grass playground and cricket pitch does not show any variation of RMSE with flying height. The RMSE for grass ground and cricket pitch is around 20mm irrespective to flying height. But, for the surface of asphalt car park and gravel driveway, the RMSE were increased with flying increases except 120m flying height. As outcome of the project, the most accurate flying height to be determined with respective to the surface texture and number of ground control points. The contours of asphalt surface and cricket ground generated by 60m images shows 20mm accuracy which give proof for application of UAV at lower altitude for unobstructed uniform surface. Further, cost, processing time, client requirement and convenience with respect to flying height is to be determined in the selection of most suitable flying height for practical application.

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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
Date Deposited: 06 Sep 2022 23:55
Last Modified: 06 Sep 2022 23:55
Uncontrolled Keywords: UAV; aerial photogrammetry; spatial science
URI: https://sear.unisq.edu.au/id/eprint/40841

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