Reference

Glossary of LiDAR and landscape archaeology

A glossary of LiDAR and landscape archaeology terms as they are used in England, from digital terrain models and sky-view factor to ridge and furrow, Historic Environment Records and map regression.

Last updated 25 October 2026

The terms run from the LiDAR data itself and the views drawn from it, through the earthworks and marks those views reveal, to the maps, records, laws, methods and licences that come with studying a place. The definitions are our own, written from the sources listed at the end. Where Field Archaeology, a research atlas for England, uses a term in its own way, or stops short of it, the entry says so after the definition. Each term can be linked on its own, for example fieldarchaeology.co.uk/glossary#sky-view-factor.

A line of round barrows on Normanton Down near Stonehenge, the mounds and ring ditches picked out in grey relief from one metre LiDAR, with tracks and field boundaries around them. — Barrows on Normanton Down, near Stonehenge, in a grey hillshade. Environment Agency one metre LiDAR, Open Government Licence v3.0.

LiDAR data

LiDAR: Light detection and ranging: measuring distance by timing pulses of laser light as they bounce back. Flown from an aircraft, as airborne laser scanning (ALS), it records the height of the ground and of everything standing on it; the name is also written lidar or LIDAR.
Point cloud: The raw result of a LiDAR survey: millions of measured points, each with a position and a height, usually supplied as LAS or LAZ files. Terrain and surface models are made from it.
First and last return: One laser pulse can echo back several times as it passes through trees or hedges. The first return comes from the first thing it meets, such as a canopy or a roof; the last usually comes from the ground, though dense vegetation or a building can stop it short.
Digital terrain model (DTM): A grid of ground heights with trees, hedges and buildings taken out, so it shows the bare earth. Most LiDAR visualisations for archaeology are drawn from one.
Digital surface model (DSM): A grid of the heights of the surface the laser met, with trees, hedges, buildings and vehicles left in. Field Archaeology's Surface model view is drawn from the Environment Agency's last-return DSM, so trees, hedges and buildings show.
Resolution: The size of one cell in a grid of heights: at 1 m there is a height for every square metre of ground. Detail much smaller than a cell or two cannot be seen.
National LIDAR Programme: The Environment Agency's survey of the whole of England at 1 m, flown in the winter months between January 2017 and February 2023. Its point clouds and its terrain and surface models are free to reuse under the Open Government Licence.
LIDAR Composite: The Environment Agency's seamless height models of England at 1 m and 2 m, made in 2022 from surveys flown between June 2000 and April 2022, using the newest and finest survey wherever surveys overlap. The 1 m terrain model covers about 99 per cent of England, and each survey in it is accurate in height to about 15 cm (root mean square error).

LiDAR visualisations

Hillshade: A height model lit by an imaginary sun from one direction, so slopes facing the light are bright and those facing away are dark, much as low winter sunlight picks out earthworks. A bank that runs in line with the light casts no shadow and can vanish. Field Archaeology's LiDAR relief is the Environment Agency's own hillshade.
Multi-directional hillshade: Hillshades lit from several directions and combined into one picture, so that no single sun angle hides a feature. Field Archaeology's Multi-light relief lights the ground from six directions at 45 degrees above the horizon and averages them.
Vertical exaggeration: Stretching heights against distances across the ground, so that low banks and shallow ditches stand out more strongly. Field Archaeology's Multi-light relief exaggerates heights two times on the 1 m grid.
Slope: The steepness of the ground at each cell, shaded from flat to steep, which outlines the sides of banks, ditches, terraces and old river channels whatever the direction of the light. It cannot tell a rise from a dip, so read it beside another view. In Field Archaeology the slope view is called Palaeochannels.
Local relief model (LRM): The ground minus a smoothed copy of itself, which takes away hills and valleys and leaves the small rises and dips of earthworks; Ralf Hesse set it out for archaeology in 2010. Field Archaeology's Local relief view is a simple local relief model, the ground minus its mean over a 41 m square.
Sky-view factor (SVF): The share of the sky that can be seen from each point of the ground: ditches and hollows see less sky and turn dark while open ground stays bright, whichever way a feature runs. Zakšek, Oštir and Kokalj set it out as a relief view in 2011. Field Archaeology's Sky view measures it in eight directions out to 12 m on the 1 m grid.
Openness: How open the ground is at a point, measured from the angles to the horizon in eight directions: positive openness looks up from the surface and is high on banks and ridges, while negative openness looks down into it and is high in ditches and hollows. Yokoyama, Shirasawa and Pike introduced it in 2002. Field Archaeology draws Positive openness and an Openness composite of both.
Red relief image map (RRIM): A view that shows slope as shades of red and openness as brightness, so ridges come out light, hollows dark and steep ground red, with no light direction to choose. Chiba, Kaneta and Suzuki published it in 2008. Field Archaeology's Red relief view is drawn after their method.
Processing artefact: A pattern made by the survey or its processing rather than by anything on the ground, such as wavy lines where flight strips overlap, which can look like ridge and furrow, or steps from rounded heights that can look like lynchets. A feature that shows on top of a modern road or hedge, rather than only on either side of it, is in the image, not the ground, and is an artefact.

Earthworks and landforms

Earthwork: A bank, ditch, mound, platform or hollow made by people that still shows in the surface of the ground, rather than surviving only buried. LiDAR, which measures height, is at its best with earthworks, and can pick out low banks that are hard to see on the ground.
Barrow: A mound of earth, turf or stone raised over one or more burials. Long barrows are rectangular or trapezoidal Neolithic mounds with ditches along their sides; round barrows, mostly of the Late Neolithic and Bronze Age, are round mounds usually ringed by a ditch.
Ring ditch: A circular ditch, usually seen as a cropmark, whose purpose is not known: it may be what is left of a ploughed-out round barrow, a roundhouse or a modern feature. Where no bank or mound survives above it, LiDAR may show nothing at all.
Hillfort: A hilltop enclosure bounded by one or more large ramparts and ditches, in England mostly of the Iron Age; with one rampart it is univallate, with more it is multivallate. Maiden Castle in Dorset is multivallate: its ramparts finally had three banks and two ditches around the hilltop.
Enclosure: An area of land marked off by a ditch, bank, wall, palisade or similar boundary, the general term until a site's purpose is known. It is not the same as the enclosure of open fields and commons, which changed how land was held.
Ridge and furrow: The long, parallel ridges left by ploughing the same strips of an open field year after year, mostly in the medieval period, the older ones often laid out in a gentle reversed S. Lit along its length in a hillshade it can disappear, so check it in a second view.
Lynchet: A bank or step that forms along the downhill edge of a ploughed field, as soil loosened by the plough creeps down the slope and builds up against the boundary. Lynchets outline many later prehistoric and Roman field systems, once called Celtic fields, and flights of strip lynchets terrace some hillsides.
Hollow way: A track or lane worn below the ground on either side by long use and running water. On LiDAR it shows as a long, shallow trough, which a local relief model brings out well.
Agger: The raised bank on which a Roman road was built. Even where ploughing has spread it, the line of an agger can often be followed on LiDAR, which has helped trace many lost stretches of Roman road.
Deserted medieval village (DMV): A village abandoned in the Middle Ages that now survives only as earthworks or cropmarks: platforms where houses stood, tofts and crofts (the house plots and the small closes next to them), and hollow ways where the streets ran.
Palaeochannel: The course of a former river or stream, since filled with sediment, which can still show on LiDAR as a shallow, winding hollow across a floodplain. In Field Archaeology the slope view is called Palaeochannels.

Marks seen from the air

Cropmark: A pattern in a growing crop over buried features: plants over a filled ditch, with deeper and damper soil, grow taller and stay green longer, while those over a buried wall are stunted. Cropmarks are differences of growth and colour, not of height, so LiDAR terrain models seldom show them.
Soilmark: A difference in the colour of ploughed or bare soil over a levelled or buried feature, such as the dark fill of a ditch or the pale material of a ploughed-out bank, seen best from the air.
Parchmark: Grass or a crop that browns early in a dry spell over buried walls, floors or roads, where the soil above them is thin and dries out first. Like cropmarks, parchmarks are seen from the air or from high ground, and seldom show in LiDAR terrain models.

Maps and grids

British National Grid: The Ordnance Survey's grid of eastings and northings in metres across Great Britain, with its origin set south-west of the Isles of Scilly so that every position is positive. GIS software knows it as EPSG:27700.
National Grid reference (NGR): A position on the British National Grid, written as the two letters of its 100 km square and then an easting and a northing within that square, such as SY 66891 88459 for Maiden Castle. Four figures give a 1 km square and ten fix a point to the metre.
Ordnance Datum Newlyn (ODN): The zero for heights on mainland Great Britain: mean sea level at Newlyn in Cornwall, measured between 1915 and 1921. The Environment Agency's LiDAR heights are given in metres above it.
OSTN15: The Ordnance Survey's definitive transformation between satellite positions (ETRS89) and the British National Grid, released in 2016, which corrects for distortions in the old national triangulation on a 1 km grid. Field Archaeology currently uses a single Helmert transformation instead, usually within 2 m of OSTN15 and up to about 4 m out in the far south-west.
County Series: The Ordnance Survey's large-scale maps of England and Wales at six inches and 25 inches to the mile, surveyed county by county from the 1840s to the 1950s. Historic maps sets out the editions and how to date a sheet.
Tithe map: A map of a parish or township made under the Tithe Commutation Act 1836, numbering every plot; the apportionment that goes with it names each plot's owner and occupier and its use.
Georeferencing: Fitting a scanned map, plan or photograph to real-world coordinates so it can be laid over other data. The National Library of Scotland, which georeferenced the Ordnance Survey maps it has scanned, notes that single features on them will not always sit exactly where they are on the ground.
Map regression: Working back from today's map through older editions to see when fields, buildings, roads and earthworks appeared or went. Archaeologists use it to date features seen on LiDAR and to set out a site's history in a desk-based assessment.

Heritage records and protection

Historic Environment Record (HER): The record of an area's known sites, finds, historic buildings, excavations and reports, kept for its council or national park and much of it on no national list; HERs grew out of the older Sites and Monuments Records.
National Heritage List for England (NHLE): The official register of England's nationally protected historic buildings and sites, kept by Historic England: listed buildings, scheduled monuments, registered parks and gardens, registered battlefields, protected wreck sites and World Heritage Sites. Each entry has a list entry number, such as 1015775 for Maiden Castle.
Scheduled monument: A nationally important archaeological site or structure protected by being added to the schedule kept under the Ancient Monuments and Archaeological Areas Act 1979. England has about 20,000, each with an entry on the National Heritage List for England.
Scheduled Monument Consent: The permission needed for works that would damage, remove, repair, alter or add to a scheduled monument, excavation included; in England it is applied for through Historic England. Carrying out such works without it is an offence under the Ancient Monuments and Archaeological Areas Act 1979.
Section 42 licence: Historic England's written consent, under section 42 of the Ancient Monuments and Archaeological Areas Act 1979, to use a metal detector or geophysical survey equipment on a scheduled monument or other protected place. The Act counts any device for finding metal or minerals in the ground as a metal detector, and using one there without consent is an offence.
Heritage at Risk Register: Historic England's yearly register of the historic buildings, monuments, places of worship, parks, battlefields, wrecks and conservation areas most at risk of being lost through neglect, decay or inappropriate development. The 2025 register, published on 6 November 2025, has 4,891 entries.
Aerial Investigation and Mapping (AIM): Historic England's mapping of archaeology from aerial photographs and LiDAR, made by its own teams and by projects it funds, to a standard once called the National Mapping Programme. It covers only the parts of England its projects have reached.
Portable Antiquities Scheme (PAS): A scheme, founded in 1997, that records archaeological objects found by members of the public in England and Wales, most of them by metal detectorists, and publishes the records online. It is managed by the British Museum in England and by Amgueddfa Cymru (Museum Wales) in Wales.
Finds Liaison Officer (FLO): A Portable Antiquities Scheme officer who records the finds people bring in from their area and advises finders, including on what to do with possible treasure.
Findspot: The recorded place where an object was found, usually given as a National Grid reference. It marks a find, not a site: on its own a findspot does not show that anything else lies there.
Treasure Act 1996: The law that decides what counts as treasure in England, Wales and Northern Ireland, chiefly objects at least 300 years old that are at least a tenth gold or silver by weight, and groups of coins of that age. Since the Treasure (Designation) (Amendment) Order 2023, a find made from July 2023 can also be treasure if it is at least 200 years old, partly made of metal and gives an exceptional insight into national or regional history, archaeology or culture. Every finder, archaeologists included, must report possible treasure to the coroner within 14 days of the find, or of realising it may be treasure.

Methods, reports and licences

Desk-based assessment (DBA): A study of what is already known about the historic environment of a site, from records, maps, aerial photographs, LiDAR and earlier reports, to judge what may survive there and how much it matters; the Chartered Institute for Archaeologists sets the standard for it. Field Archaeology's area report can be a starting point, but it is not a search of the Historic Environment Record, which an assessment is expected to consult.
Walkover survey: A planned walk over a defined area to find sites not yet recorded and to check the condition of known ones. The standard for desk-based assessment expects a visit to the study area unless access is restricted.
Fieldwalking: Walking a ploughed field in lines or on a grid and collecting the pottery, flint and other finds lying on the surface, each logged by where it was found, to map where people were active in the past.
Geophysical survey: Mapping buried features from the surface without digging, most often with a magnetometer, an earth resistance meter or ground-penetrating radar. On a scheduled monument it needs a section 42 licence.
Historic Landscape Characterisation (HLC): Mapping the whole of today's landscape by its historic character, such as the origin and age of its field patterns, to understand it and to guide change.
Grey literature: Reports of fieldwork and research that are not formally published. Many are indexed through OASIS and held in the Archaeology Data Service library. Field Archaeology does not include them, so look for them before relying on the map.
Archaeology Data Service (ADS): An accredited digital archive for archaeology and historic environment data, founded in 1996 and based at the University of York.
Open Government Licence (OGL): The licence under which UK public bodies such as the Environment Agency and Historic England publish much of their data: anyone may copy, adapt and use it, commercially too, if they acknowledge the source as asked and do not suggest that the publisher endorses them. Data and licences sets out what it and the other licences allow.
Creative Commons Attribution (CC BY): A licence that lets anyone share and adapt a work for any purpose, commercial use included, so long as they credit it, link to the licence and say what they changed. How to cite explains how to credit a source.

Sources

Ancient Monuments and Archaeological Areas Act 1979, c. 46, sections 1, 2 and 42. Available at: https://www.legislation.gov.uk/ukpga/1979/46 (Accessed: 25 October 2026).
Archaeology Data Service (no date) About. Available at: https://archaeologydataservice.ac.uk/about/ (Accessed: 25 October 2026).
Archaeology Data Service (no date) OASIS. Available at: https://archaeologydataservice.ac.uk/about/projects/oasis/ (Accessed: 25 October 2026).
Chartered Institute for Archaeologists (2020) Standard and guidance for historic environment desk-based assessment. Reading: CIfA. Available at: https://www.archaeologists.net/sites/default/files/2023-11/CIfA-SandG-DBA-2020.pdf (Accessed: 25 October 2026).
Chiba, T., Kaneta, S. and Suzuki, Y. (2008) ‘Red relief image map: new visualization method for three dimensional data’, International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 37(B2), pp. 1071 to 1076. Available at: https://www.isprs.org/proceedings/XXXVII/congress/2_pdf/11_ThS-6/08.pdf (Accessed: 25 October 2026).
Creative Commons (no date) Attribution 4.0 International. Available at: https://creativecommons.org/licenses/by/4.0/ (Accessed: 25 October 2026).
Environment Agency (no date) National LIDAR Programme. Available at: https://www.data.gov.uk/dataset/f0db0249-f17b-4036-9e65-309148c97ce4/national-lidar-programme (Accessed: 25 October 2026).
Environment Agency (2022) LIDAR Composite Digital Terrain Model (DTM), 1m. Available at: https://www.data.gov.uk/dataset/01b3ee39-da3f-47b6-83da-dc98e73a461f/lidar-composite-digital-terrain-model-dtm-1m (Accessed: 25 October 2026).
Hesse, R. (2010) ‘LiDAR-derived local relief models: a new tool for archaeological prospection’, Archaeological Prospection, 17(2), pp. 67 to 72. Available at: https://doi.org/10.1002/arp.374.
Historic England (2018) Using Airborne Lidar in Archaeological Survey: The Light Fantastic. Swindon: Historic England. Available at: https://historicengland.org.uk/images-books/publications/using-airborne-lidar-in-archaeological-survey/ (Accessed: 25 October 2026).
Historic England (2025) Heritage at Risk: latest findings. Available at: https://historicengland.org.uk/listing/heritage-at-risk/findings/ (Accessed: 25 October 2026).
Historic England (no date) Aerial Investigation and Mapping. Available at: https://historicengland.org.uk/research/methods/airborne-remote-sensing/aerial-investigation/ (Accessed: 25 October 2026).
Historic England (no date) The National Heritage List for England. Available at: https://historicengland.org.uk/listing/the-list/ (Accessed: 25 October 2026).
Historic England (2026) National Heritage List for England, list entry 1015775: Maiden Castle. Available at: https://historicengland.org.uk/listing/the-list/list-entry/1015775 (Accessed: 25 October 2026).
Historic England (no date) FISH Thesaurus of Monument Types. Heritage Data. Available at: https://www.heritagedata.org/live/schemes/eh_tmt2.html (Accessed: 25 October 2026).
Historic England (no date) FISH Evidence Thesaurus. Heritage Data. Available at: https://www.heritagedata.org/live/schemes/eh_evd.html (Accessed: 25 October 2026).
Historic England (no date) FISH Event Types Thesaurus. Heritage Data. Available at: https://www.heritagedata.org/live/schemes/agl_et.html (Accessed: 25 October 2026).
Kokalj, Ž. and Hesse, R. (2017) Airborne laser scanning raster data visualization: a guide to good practice. Ljubljana: Založba ZRC. Available at: https://doi.org/10.3986/9789612549848.
National Library of Scotland (no date) Ordnance Survey maps: six-inch England and Wales, 1842 to 1952. Available at: https://maps.nls.uk/os/6inch-england-and-wales/ (Accessed: 25 October 2026).
National Library of Scotland (no date) Historic Maps API. Available at: https://maps.nls.uk/projects/api/ (Accessed: 25 October 2026).
Ordnance Survey (2020) A guide to coordinate systems in Great Britain. Version 3.6. Southampton: Ordnance Survey. Available at: https://www.ordnancesurvey.co.uk/documents/resources/guide-coordinate-systems-great-britain.pdf (Accessed: 25 October 2026).
Portable Antiquities Scheme (no date) About us. Available at: https://finds.org.uk/about-us (Accessed: 25 October 2026).
The National Archives (no date) Open Government Licence for public sector information, version 3.0. Available at: https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/ (Accessed: 25 October 2026).
The National Archives (no date) Tithes. Research guide. Available at: https://www.nationalarchives.gov.uk/help-with-your-research/research-guides/tithes/ (Accessed: 25 October 2026).
Treasure Act 1996, c. 24, sections 1, 3 and 8. Available at: https://www.legislation.gov.uk/ukpga/1996/24 (Accessed: 25 October 2026).
The Treasure (Designation) (Amendment) Order 2023, SI 2023/404. Available at: https://www.legislation.gov.uk/uksi/2023/404/made (Accessed: 25 October 2026).
Yokoyama, R., Shirasawa, M. and Pike, R.J. (2002) ‘Visualizing topography by openness: a new application of image processing to digital elevation models’, Photogrammetric Engineering and Remote Sensing, 68(3), pp. 257 to 265.
Zakšek, K., Oštir, K. and Kokalj, Ž. (2011) ‘Sky-view factor as a relief visualization technique’, Remote Sensing, 3(2), pp. 398 to 415. Available at: https://doi.org/10.3390/rs3020398.