The geometric correction of the stereo-optical Gokturk-2 satellite images and their 3D position accuracy analysis

Acquiring knowledge in the field of satellite and space technologies, gaining the necessary experience by using this knowledge in the most efficient way, and signing the original projects with these experiences are among the scientific and economic targets of many countries in the world. Turkey has reached this originality, that very few countries have, through the BİLSAT, RASAT and GÖKTÜRK-2 satellites. After the RASAT, Turkey's second native-made geospatial observation satellite, GÖKTÜRK-2 has three times higher spatial resolution (2.5 m) than the RASAT and has a much more advanced stereo vision capability. However, in GÖKTÜRK-2, like every optical imaging satellites, data quality problems exist such as sensor geometry, contrast, dense forest cover in the field of view and topographic slope. In this study, it is aimed to generate three-dimensional Digital Surface Models (DSM) from GÖKTÜRK-2 stereo images in the Derik district of Mardin province with high slope and varying topographic conditions, and evaluate horizontal and vertical position accuracy performance evaluation using a reference DSM generated from the traditional aerial photogrammetry. The orientation of the GÖKTÜRK-2 satellite images was carried out with three-dimensional affine transformation and 18 Ground Control Points (GCP) were collected from GoogleEarth images. After the orientation process, DSM with 5 m grid was generated from the GÖKTÜRK-2 stereo images. The performance of the generated DSM is evaluated visually and statistically using the reference DSM with 0.5 m grid, which is produced from aerial photographs obtained from an altitude of 800 m using the digital aerial camera. As a result of visual evaluations, height error maps are produced. As a result of statistical investigations, the positioning accuracy of GÖKTÜRK-2 DSM was calculated with standard deviation and normalized median absolute deviation formulas. According to these achieved results, the performance of GÖKTÜRK-2 DSM in the steep and mountainous topography and in the flat urban area has been demonstrated by visual and statistical approaches.