Utvärdering av digitala terrängmodeller framtagna med flygburen laserskanning och UAS-fotogrammetri
Sammanfattning: Over the last years there has been a rapid development in the UAS-technology (Unmanned Aircraft Systems) and today there are several UAS systems on the market. The fast development has led to differences in both price and capability of taking high-quality images between the systems. The purpose of this study was firstly to investigate how two UAS systems differ in the uncertainty of measurement while making digital terrain models, secondly, to investigate how different UAS systems cope with the laws and requirements that exist for producing digital terrain models for detail projection, SIS-TS 21144:2016 Table 6 level 1-3. A comparative study on two software’s creation of point clouds from picture data was also conducted. In this study, three digital models were made from one specific area. They were created with two different UAS-systems and laser scanning from an airplane. The models were compared and analysed using the RUFRIS method. The UASsystems used were a fixed wings Smartplanes S1C and a rotary wings Dji Phantom 4 PRO. The Smartplanes flew 174 m above the ground and the Dji Phantom 4 flew 80 m above the ground. The results from the study show that laser scanning from the airplane created the model with the lowest measurement uncertainty and met all the requirements for each separate type (asphalt, natural soil, grass and gravel) for detail projection according to SIS.TS 201144:2016 table 6 level 1-3. Additionally, the results show that the terrain model produced by the Dji Phantom 4 only met the requirements for asphalt where the mean deviation was 0,001 m. The results produced with “Smartplanes” met the requirements for asphalt and gravel where the mean deviations were -0,007 m and 0,017 m. The softwares PhotoScan and UASMaster were compared while creating point clouds from pictures taken by the Smartplanes. The results show that PhotoScan had the lowest uncertainty for asphalt, grass and gravel surfaces while UASMaster produced lower uncertainty for natural soil. The results indicate that airborne laser scanning should be the preferred method for collection of topographic data since it created lower measurement uncertainties than the other methods in this study. It is also possible to create digital terrain models with UAS for detail projection for asphalt and gravel surface in accordance with 21144:2016. Finally, it was concluded that the used software programs are showing differences in creating point clouds.
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