Home Guides How to read a LiDAR map
How to read a LiDAR map
A LiDAR map shows the shape of the ground. Reading it well is a matter of knowing what has been removed, how the picture was lit, and what else to check before deciding what a feature is.
What you are looking at
The LiDAR layers in Waystone are digital terrain models: grids of ground height at one metre per pixel, made by removing the laser returns from vegetation and buildings. A terrain model has no colour of its own. Every LiDAR image is a picture computed from the heights, and the method of computing it decides what you see.
The light changes the picture
A hillshade lights the terrain from one direction, like a low sun. Banks facing the light are bright, slopes facing away are dark, and a bank running straight towards the light casts almost no shadow and can disappear. Turn the sun round before deciding that something is not there. A low sun shows small earthworks better than a high one. When the light comes from the bottom of the screen (from the south), many people see ditches as banks and banks as ditches, which is why hillshades are usually lit from the north-west.
Use more than one reading
Methods that do not depend on one light direction are better for finding features: multidirectional hillshading, the local relief model (SLRM), sky-view factor, openness and the VAT composite. See LiDAR visualisations explained.
Separate modern features from earthworks
The terrain model keeps everything that is part of the ground: roads, railway cuttings, field drains, quarries, spoil heaps, golf bunkers, embanked tracks and the footings of modern buildings. Laying the LiDAR over the satellite photograph, and over the Ordnance Survey six-inch maps of 1843–1913, shows which features are modern or were already there in the nineteenth century.
Check the records
Many features you can see are already recorded. Click the pins near a feature to read the heritage records, and check the aerial archaeology layer, which maps features traced by Historic England from aerial photographs and LiDAR. A feature that appears in no record is not necessarily new: it may be modern, natural, or recorded under a different name.
What LiDAR cannot tell you
- The date of a feature. A bank of the Iron Age and a bank of the 1950s can look the same.
- What lies below the surface where nothing shows as height. Ploughed-out sites often show only on aerial photographs as cropmarks.
- Features smaller than the grid. At one metre per pixel, features a metre or two across are at the limit.
Visiting what you find
Most land is private: use public rights of way. Scheduled monuments are protected by law: in England under the Ancient Monuments and Archaeological Areas Act 1979, and in Wales under the Historic Environment (Wales) Act 2023, which replaced the 1979 Act there on 4 November 2024. Damaging one, or using a metal detector on one without consent, is a criminal offence. If you think you have found an unrecorded site, report it to the local Historic Environment Record.
Related
Sources
- Environment Agency, National LIDAR Programme and LIDAR Composite DTM (1 m), Open Government Licence. © Environment Agency copyright and/or database right.
- Natural Resources Wales and Welsh Government LiDAR (1 m), Open Government Licence. Contains Natural Resources Wales information © Natural Resources Wales and Database Right.
- Historic England (2018). Using Airborne Lidar in Archaeological Survey: The Light Fantastic. Swindon: Historic England.
- Hesse, R. (2010). LiDAR-derived Local Relief Models: a new tool for archaeological prospection. Archaeological Prospection 17(2), 67–72.
- Zakšek, K., Oštir, K. and Kokalj, Ž. (2011). Sky-View Factor as a relief visualization technique. Remote Sensing 3(2), 398–415.
- Kokalj, Ž. and Somrak, M. (2019). Why not a single image? Combining visualizations to facilitate fieldwork and on-screen mapping. Remote Sensing 11(7), 747.
Last updated 2026-10-16.