Footprint

The patch of ground a single instrument sample covers. For a lidar like GEDI it’s a ~25 m circle; for a sounder it can be tens of kilometres.

Why it matters

Footprint-sampled instruments measure spots, not continuous images — so coverage is sparse and you interpolate between footprints rather than reading a full map.

In plain terms

One footprint = one “ping” of the instrument touching the ground, like a single fingerprint pressed onto a surface.