'LiDAR' (Light Detection and Ranging) from an airborne platform produces:
Choose the correct answer
Only 2D satellite imagery with no elevation
Dense 3D point cloud with multiple returns — separate DSM (surface) and DTM (bare earth) from first/last returns
Only colour photographs from the aircraft
Temperature map of land surface
Correct Answer
B. Dense 3D point cloud with multiple returns — separate DSM (surface) and DTM (bare earth) from first/last returns
Why is this the answer?
Airborne LiDAR: laser pulses emitted, time to return measured → range R = c×t/2. Multiple returns: first return (top of canopy), last return (ground even under forest). Dense point cloud: 10–50 points/m². Products: (1) DSM (Digital Surface Model — top of everything); (2) DTM/DEM (Digital Terrain Model — ground after filtering vegetation/buildings); (3) Intensity image; (4) Building footprints. Accuracy: ±15 cm vertical, ±30 cm horizontal. Much faster than conventional survey for large areas.
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