'Structure from Motion' (SfM) photogrammetry using a drone (UAV) automatically produces:
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Only 2D planimetric map without height
Dense 3D point cloud, DEM, and orthophoto automatically from overlapping drone photos — cm accuracy with GCPs
Only video recording without measurement
Thermal infrared images of ground
Correct Answer
B. Dense 3D point cloud, DEM, and orthophoto automatically from overlapping drone photos — cm accuracy with GCPs
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SfM photogrammetry: drone captures overlapping photos from multiple viewpoints; software (Agisoft Metashape, Pix4D) automatically: (1) Extracts feature points (SIFT algorithm); (2) Matches across photos; (3) Computes camera positions (bundle adjustment); (4) Generates dense point cloud; (5) Creates DEM + orthophoto. With few GCPs: cm-level accuracy. Rapid, cost-effective replacement for manned aircraft survey for small areas.
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