Kvalitetsjämförelse av markmodeller skapade med digital fotogrammetri : En jämförelse av mätosäkerhet på markmodeller med bilder ifrån olika UAVs
Sammanfattning: In recent years, the technical progress of Unmanned Aerial Vehicles (UAV) has increased rapidly. This has made it economically possible for tasks where one earlier needed helicopters or airplanes. By equipping UAVs with high-quality cameras, the utility has expanded. With detailed photos from a UAV together with digital photogrammetry, special software can be used to create point clouds, 3D-models, elevation models and ortomosaics over smaller geographic areas. Due to the easy access and that the use of UAVs has increased among private users, the Swedish transport agency has set up rules that determine how UAVs should be used. In these regulations, UAVs are separated into different groups from A1 to A3 based on the weight of the aircraft. The regulations make it illegal to fly a UAV heavier than 250 g over people who are not informed about the flight. Since there are several industries where it could be interesting to fly over people, DJI has manufactured a UAV-model called DJI Mini 2. This UAV weighs 249 g and can therefore be flown over people. In this project, two different flights have been carried out. One with the DJI Mini 2 weighing 249 g and one with the DJI Mavic 2 Pro weighing just under 1 kg. During the flight, overlapping pictures were captured and orthomosaic and elevation models were created from those. The purpose of the project was to investigate if the same accuracy can be achieved with a mini-UAV as with a larger UAV. The study also investigated whether the models were accurate enough to use as a ground model along roads and railroads. In the Dronelink software, two different flight routs were created over Örsholmens IP in the eastern part of Karlstad, Sweden. Dronelink created the flightpath based on the UAVs different specifications and the overlap between images that were acquired. A geodetic control network was created using GNSS-technology. Five points were measured twice with 45 minutes in between and calculated in SBG GEO. The next day, a surveying total station was established centrally between the points in the geodetic control network. Thereafter 19 ground control points were measured, and 398 ground points distributed in 20 different control profiles. After the points were measured, the flights were carried out. A total of two flights by each UAV model were made the same day. Then the flight with the best results were used for further processing. The photos taken were processed in Agisoft Metashape. In the software, point clouds, elevation models and orthomosaic were created. The elevation model was then compared to the measured control profiles. The orthomosaic was used to compare the ground control points. The results showed that the elevation model created with Mavic 2 Pro was within the SIS tolerance on all different types of surfaces to be used for modelling along roads and railways. The elevation model from the DJI Mini 2 was withing the tolerance on grass and asphalt but not on gravel surface. The mean deviation on gravel was -1,37 cm outside the tolerance. The planar comparison showed that both models were withing the tolerance to achieve HMK level 3 standard.
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