What is Multi-Return LiDAR?

Multi-return LiDAR captures multiple echoes from a single laser pulse, letting you see through vegetation to the ground below. When a pulse enters a forest canopy, part of the energy bounces back from leaves at the top, part from branches in the middle, and part continues down to reach the earth. Each echo becomes a separate point in your dataset.

How Multi-Return Works

A laser pulse isn't a perfect line — it spreads slightly as it travels, creating a footprint that may illuminate objects at different heights simultaneously. When the return signal reaches the sensor, it contains distinct peaks corresponding to reflections from different surfaces. The sensor detects and timestamps each peak, recording them as separate returns tagged with their sequence number.

Modern LiDAR systems typically record 4-7 returns per pulse, though the actual number depends on what the pulse encounters. A pulse hitting open ground produces a single return. A pulse passing through a complex forest canopy might produce five or six. Each return carries metadata: its sequence number (1st, 2nd, 3rd…), the total number of returns for that pulse, and often the return intensity.

Why It Matters

Without multi-return capability, you'd only see the top of forests — no ground points, no terrain model possible. The ability to record last returns that reach through dense canopy enables accurate DTMs in forested areas. Return number also aids classification: first returns typically represent canopy; last returns typically represent ground. This information helps algorithms distinguish vegetation from terrain even in challenging conditions.

Multi-Return Analysis with LidarVisor

LidarVisor preserves and utilizes return information for better ground classification. Filter points by return number to isolate canopy layers or analyze vegetation structure from crown to forest floor.