LiDAR, Light Detection and Ranging, builds 3D maps by firing millions of laser pulses and measuring how long they take to bounce back. It sees through forest canopy, maps terrain to centimetre accuracy, and now fits in a phone. From archaeology to self-driving cars, LiDAR is quietly remaking how we measure the world. This guide explains how it works and what it is used for.

How LiDAR Works

A LiDAR sensor fires rapid pulses of laser light and measures the time each pulse takes to return, converting the time into a distance. Millions of pulses per second build a point cloud, a 3D model of everything the laser touched. Airborne LiDAR mounts the sensor on a plane or drone, terrestrial LiDAR uses a tripod, and mobile LiDAR mounts it on a vehicle. The result is a dense, accurate 3D model of the landscape, a building, or a forest.

Seeing Through the Forest

LiDAR's most famous ability is seeing through vegetation: some laser pulses hit the canopy, but others pass through gaps and hit the ground, so the point cloud contains both the trees and the terrain beneath them. Archaeologists use this to find ancient cities hidden under jungle, and foresters use it to measure tree height and biomass. No camera can do this, because a photograph shows only the top of the canopy. LiDAR sees the ground that the camera cannot.

LiDAR in Your Phone and Car

Modern smartphones include a LiDAR sensor that measures depth for photography, augmented reality, and room scanning. Self-driving cars use larger LiDAR units to build a real-time 3D map of the road, detecting vehicles, pedestrians and obstacles. The technology that once required an aircraft now fits in a pocket, and the price has fallen from tens of thousands to hundreds of dollars, which is why it is spreading so fast.

LiDAR vs Photogrammetry

LiDAR and photogrammetry, building 3D models from overlapping photographs, are the two main ways to make 3D maps, and they suit different jobs. LiDAR is more accurate, works in low light, and sees through vegetation, but it is more expensive and produces no colour imagery by itself. Photogrammetry is cheaper, produces full-colour models, and works with an ordinary drone camera, but it cannot see through trees and struggles in flat, featureless terrain. Many projects use both: LiDAR for terrain, photogrammetry for texture.

Getting Started With LiDAR Data

Free LiDAR data is available from many governments: the USGS 3DEP programme covers much of the United States, and several European countries publish open LiDAR. QGIS handles point clouds natively, and the PDAL library processes them from the command line. Start by downloading a free tile, visualising it in QGIS, and extracting a ground model: the first time you see the terrain beneath a forest, you will understand why LiDAR matters.

LiDAR and Archaeology

LiDAR has transformed archaeology: the laser pulses penetrate forest canopy, revealing ancient cities, roads, and fields that were invisible from the air. In Central America, LiDAR surveys have revealed Maya cities that were hidden for a thousand years, and the discoveries are rewriting the history of the region. The technology is expensive, but the data is increasingly free, and the archaeological applications are only beginning. LiDAR is not just a mapping tool, it is a time machine that reveals the past.

Key Takeaways

- LiDAR measures distance with laser pulses, building a 3D point cloud - It sees through forest canopy to the ground beneath - Modern phones include LiDAR; self-driving cars depend on it - LiDAR is more accurate than photogrammetry but more expensive

Frequently Asked Questions

What is LiDAR used for? Mapping terrain, finding archaeology under forests, measuring trees, guiding self-driving cars, and building 3D models of buildings and landscapes.

LiDAR is a laser that sees what cameras cannot. It maps the ground beneath the forest, and it now fits in your phone.