LiDAR
Definition
Radar with laser light — self-driving cars paint the world in 3D with millions of light pulses per second.
Technical definition
Time-of-flight ranging: d = cΔt/2 per pulse; scanning builds point clouds. Typical wavelengths are ~905 or 1550 nm.
Example
Archaeologists found entire Mayan cities under jungle canopy with airborne LiDAR — laser pulses slipped through leaves and mapped stone beneath.
Common confusion
LiDAR can't see through walls — it needs line of sight. It maps surfaces by timing reflections, like echolocation with light.