3D point cloud History of engineering & technology KOMPSAT-3A RPCs SAR image SAR imagery Sentinel-2 Technology: general issues aerial orthoimage backpack-based mapping computational simulation denoising detection discrepancy fusing region proposals high-resolution image fusion image simulation in situ self-calibration interferometry matching mobile mapping system mosaic multi-beam LiDAR panchromatic image random forest regression remote sensing residual U-Net sensor modeling strip