LiDAR and Elevation Mapping

LiDAR (Light Detection and Ranging) measures distance by emitting a laser pulse, usually in the near-infrared near 1064 nanometers, and precisely timing how long it takes the reflected light to return to the sensor; multiplying that time-of-flight by the speed of light yields the range to whatever the pulse struck. Because a single downward pulse fired over vegetated terrain can generate several distinct returns as it passes through gaps in the canopy before finally reaching bare ground, LiDAR systems typically record multiple returns per pulse, with the first return generally corresponding to the canopy top and the last to the ground surface beneath it. This multiple-return capability is what distinguishes LiDAR from passive optical and even radar imaging for structural measurement: rather than producing a single flat reflectance image, it directly yields a three-dimensional point cloud of the surveyed area.