| dc.description.abstract | Structure-from-Motion (SfM) is a photogrammetric range image technique used for high-resolution 3D modeling, where the 3D information is obtained from sequences of overlapping 2D optical images captured from different angles. In geoscience application, SfM is considered a reforming technique for surface modeling due to its effectiveness, low-cost, and user-friendly approach. The last decade has witnessed an extensive popularization of SfM photogrammetry concerning geoscience, and several studies have followed regarding SfM for different applications. Today, several photogrammetric software packages are available for performing the SfM reconstruction from 2D images to 3D modeling. This study aimed to investigate if SfM photogrammetry is an acceptable tool for studying changes of a permafrost-landform known as a palsa, over time in a challenging marshland area within a threshold of 10 centimeters in x, y, and z-direction. The work from this thesis was carried out by generating a total of eight digital terrain models and orthoimages using two photogrammetric software packages (Agisoft Photoscan and Inpho UASMaster) from Suossjavri, Finnmark, in northern Norway (69,38 N, 24,25 E) in a timeframe of four years. The aim was answered by analyzing the generated model’s accuracy through analytical methods in ArcMap and MatLab such as difference-maps, checkpoint validation, terrain profiles, and height accuracy assessment. The results showed that the generated digital elevation models' z-accuracy exceeded the threshold of 10 cm from both software packages. However, both software packages were able to generate digital terrain models and orthoimages with an acceptable accuracy of 3 – 8 cm in x and y-direction. These results suggest that visual interpretations and horizontal measurements from the generated orthoimages are the most valid approach for studying the palsa’s changes over time. Besides, applying SfM photogrammetry on a marshland area was found to be highly challenging due to variations in water-level and vegetations, and the difficulties of using tolerable reference points. This thesis found that both Agisoft Photoscan and Inpho UASMaster were both able to generate DTMs and orthoimages with similar accuracies. However, Agisoft Photoscan was shown to produce marginally higher accuracies in the z-direction. Further remarks concludes that Agisoft Photoscan is more user-friendly compared to Inpho UASMaster due to a pleasant user-interface, highly automated processing steps, and a straightforward workflow. | eng |