Large Scale Topographic Mapping Using Stereo Pair Imagery from CAS500-1 Satellite

A CAS500-1 (Compact Advanced Satellite) is a high-resolution Earth-observing satellite launched in Mar 2021 and being operated by National Land Satellite Center at NGII (National Geographic Information Institute). The mission of the satellite is the periodic monitoring of the land for efficient managements. Having completed the calibration and validation processes, CAS500-1 has been acquiring land images to generate the basic geospatial information that are topographic maps, orthorectified images, and DEM (Digital Elevation Model). Using satellite data has a lot of advantages over aerial images in terms of repeatability, coverage, and accessibility. However, the spatial resolution is relatively lower than that of aerial images. This prohibits the large scale topographic mapping from the satellite data. Therefore, we conducted 1:5,000 large scale topographic mappings using CAS500-1 stereo data and assessed the accuracy. Two test areas were selected including accessible and inaccessible areas. Overlapping CAS500-1 data were automatically processed with GCP (Ground Control Points) chips for better positional accuracy. Then they are used for the epipolar resampled images that can be used for stereo-plotting. Through the stereo display quality assessment, we selected the optimal stereo set for each site. The accuracy of the resulted topographic maps was checked using ground truth data such as GNSS (Global Navigation Satellite System)-surveyed points over the accessible area and GCP chips in the inaccessible area, respectively. The experimental results showed the accuracy successfully met the requirement of 1:5,000 topographic map in Korea. We concluded that CAS500-1 data will have more potential for large scale mapping considering that CAS500-2 is scheduled to be launched in 2022 and cooperate with CAS500-1.