LiDAR, which measures distance with laser pulses from aircraft or satellites, produces point clouds that reveal terrain, vegetation structure, buildings and archaeology in three dimensions. A decade ago this data was expensive and scarce. Today, government open-data programmes have released enormous LiDAR archives for free, and knowing where to look is the main barrier to using them.

The value of LiDAR over imagery is that it sees through vegetation. Aerial LiDAR pulses partly penetrate tree canopies and return ground hits, letting analysts build bare-earth elevation models under forest that no photograph can provide. Archaeologists use this to find earthworks hidden by woodland; flood modellers use it for precise terrain; foresters use canopy height models derived from the same clouds.

In the United States, the USGS 3D Elevation Program, known as 3DEP, is the flagship source, distributing quality level 1 and 2 LiDAR for much of the country through The National Map and EarthExplorer. NOAA's Digital Coast offers coastal LiDAR, and many states run their own portals with even higher-resolution local collections. Search by county or watershed, since coverage is organised administratively.

Europe's coverage is more fragmented but growing fast. The United Kingdom's Environment Agency publishes open LiDAR for England, the Netherlands offers the AHN national elevation dataset, and several other countries maintain national portals. The European Union's Copernicus programme and the Global Ecosystem Dynamics Investigation, or GEDI, satellite provide spaceborne LiDAR with global coverage at coarser resolution, useful for regional studies.

Other regions have strong sources too. Australia's Geoscience Australia and state programmes publish LiDAR for many areas, New Zealand's Land Information service offers national elevation data, and OpenTopography, a US National Science Foundation facility, aggregates research-grade LiDAR from around the world with tools for clipping and processing. OpenTopography is an excellent first stop when you are unsure where a region's data lives.

Working with point clouds in QGIS starts with the LAStools or PDAL processing tools. Load a LAZ or LAS file, inspect point classification, ground points are usually class 2, and generate a digital terrain model from ground returns only, or a digital surface model from all returns. For large clouds, tile the data and process in chunks rather than loading everything at once.

File sizes demand respect. A single LiDAR tile can run to hundreds of megabytes, and a county collection to tens of gigabytes. Download only the tiles you need, keep them on fast storage, and consider cloud-optimised formats or databases like Entwine Point Tiles for repeated access. Disk space and patience are the real costs of free LiDAR.

Start with one tile over a familiar area, build a hillshade and a canopy height model, and compare them against imagery you know. Once you see a hidden track under trees or a precise floodplain edge that imagery never showed, you will understand why LiDAR has become essential to modern GIS.

LiDAR beginners should also know about the Global Ecosystem Dynamics Investigation, or GEDI, data from the International Space Station, which provides free canopy height and structure samples worldwide. It is coarser than airborne LiDAR but covers regions with no national programme, making it a valuable fallback for global or tropical studies where local data does not exist. Pairing LiDAR with imagery and field checks gives the most reliable picture of all, since each source covers the weaknesses of the others. OpenTopography in particular is worth bookmarking, since it gathers research-grade collections that are otherwise scattered across university and agency servers in different formats. Start with a small, familiar area and expand from there.