{"id":23,"date":"2017-07-12T16:47:54","date_gmt":"2017-07-12T15:47:54","guid":{"rendered":"http:\/\/themedemos.webmandesign.eu\/reykjavik\/?page_id=23"},"modified":"2025-03-05T11:31:19","modified_gmt":"2025-03-05T11:31:19","slug":"how-to-use-lidar-data","status":"publish","type":"page","link":"https:\/\/www.lidar.cymru\/arfordirpenfro\/how-to-use-lidar-data\/","title":{"rendered":"Find out more about Lidar"},"content":{"rendered":"
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A Lidar sensor uses a laser to measure the distance between the aircraft and the ground. By recording millions of these measurements we can create a record of the relative heights of the ground surface. The laser also reflects off trees and buildings, cars, cows and cursus monuments \u2013 anything present in the landscape at the time of the survey is recorded. This means that the models must be interpreted by humans to make sense of the information they contain.

The Lidar models have been processed into a series of images that help us to make sense of the topography. The images used in the portal are described below.
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Multi-direction hillshades of the surface model (containing all vegetation and buildings) and the terrain model (just the ground surface with all vegetation and buildings digitally removed). A multi-direction hillshade combines the modelled illumination from three sun directions to make a colour image to assess both big changes in the landscape like hills and valleys ( known as macro-topography) and small changes that can represent human actions over millennia (known as microtopography).

Local Relief Model (LRM) of the terrain data accentuates small scale changes in a clear image where positive features (banks, boundaries) are white and negative features (ditches, pits) are dark. This image is particularly suited to identifying subtle archaeological features.<\/p>\n<\/div>\n<\/div>\n<\/div>\n\n\n

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Lidar technology<\/h3>\n\n\n\n

Lidar (Light Detection and Ranging) is based on the principle of measuring distance through the speed and intensity recorded for a pulse of light to be fired from sensor equipment and reaching a target, before sending a return signal.<\/p>\n\n\n\n

\"Lidar<\/figure>\n<\/div>\n<\/div>\n<\/div>\n\n
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\"Airborne<\/figure>\n<\/div><\/div>\n\n\n\n
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Airborne scanning<\/h3>\n\n\n\n

Airborne Lidar systems rely on lasers to measure distance from the sensor to a target, in this case the ground and any features upon it. Lidar sensors commonly operate by scanning a laser beam from side to side as an aircraft flies over the survey area and recording the reflections. A cloud of height points is created from these reflections which can then be turned into 3D models of the landscape.<\/p>\n<\/div>\n<\/div>\n<\/div>\n\n\n

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Global Positioning Systems<\/h3>\n\n\n\n

Although Lidar systems were developed in the 1960s, it was the widespread developments in Global Positioning Systems in the late 1980s that allowed for the creation of the highly accurate land surface models which we are familiar with today.<\/p>\n<\/div>\n\n\n\n

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\"Global<\/figure>\n<\/div><\/div>\n<\/div>\n<\/div>\n\n\n
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In the UK, it was The Environment Agency who instigated the widespread use topographic Lidar from 1996 onwards for the production of terrain maps to assess flood risk. In 2024, Natural Resources Wales completed their first complete coverage of Wales at 1m resolution, providing an incredible resource for understanding the historic environment in Wales. Although it is particularly well-known and useful in wooded areas, Lidar can also assist archaeologists in recognising earthworks and other features otherwise difficult to detect in open ground.<\/p>\n\n\n\n

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Digital Surface Model (DSM) showing Vegetation and Buildings<\/figcaption><\/figure>\n<\/div><\/div>\n\n\n\n
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Digital Terrain Model (DTM) with Vegetation and Buildings removed<\/figcaption><\/figure>\n<\/div><\/div>\n<\/div>\n\n\n\n

In order to visualise the data easily, a surface is created which can be modelled and shaded as a raster image. The most common raster images differ based on the point at which the pulses are returned to the sensor and the resulting data is processed. The Digital Surface Model (DSM) is the first return or highest point of pulse return, usually showing the whole landscape, including the ground surface in open areas, vegetation, woodland canopy and buildings. The Digital Terrain Model (DTM) is created by filtering the lidar dataset to remove all non-ground returns such as those that are reflected from vegetation and buildings. This filtering allows features under the vegetation canopy to be visualised.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n\n

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Find out more!<\/h3>\n\n\n\n

To find out more about how lidar can be used to understand the landscape and identify archaeological features join the Arfordir Penfro portal volunteers to take our online training course.<\/a><\/p>\n<\/div>\n<\/div>\n<\/div><\/div><\/div>\n\n\n\n

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Arfordir Penfro
Lidar Portal<\/h2>\n\n\n\n

The data captured during the survey are processed into high-resolution (25cm) models of the land surface that allow for the small physical traces left by past communities to be mapped. Features such as banks, ditches, pits, mounds can be identified even when they are covered by vegetation.<\/p>\n\n\n\n

Lidar survey has been revolutionary to our understanding of past human activity due to landscape-wide scale and the holistic nature of the data captured. There have been many examples of lidar for archaeology over the last two decades but this project is the first time that one of the unique archaeological landscapes of the National Park have been surveyed at such a high resolution.<\/p>\n<\/div>\n\n\n\n

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However the wealth of information in the lidar models needs to be captured and interpreted to be of real use to anyone wanting to understand the landscape and this is where our amazing volunteer citizen scientists step in. The National Park have created this Lidar portal and learning materials to help anyone access this incredible resource. In return, you can contribute to the creation of a lasting legacy of archaeological information by mapping potential sites on the portal and joining our field surveyors to assess them on the ground. The information gathered for this project will allow us to better manage and protect this special historic landscape for future generations to enjoy and explore.<\/p>\n<\/div>\n<\/div>\n<\/div><\/div><\/div>\n\n\n\n

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Get involved<\/h2>\n\n\n\n


Become a \u2018citizen scientist\u2019 and help to discover, understand, and preserve the cultural heritage of the Pembrokeshire Coast National Park, by exploring the Lidar mapping and identifying new and exciting archaeological sites.<\/p>\n\n\n\n

Find out more<\/a><\/p>\n\n\n\n

<\/div>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"
\nAirborne Lidar is a survey method that allows us to make highly accurate 3D models of the ground surface. These models show traces of human activity that help us to understand how communities use the landscape in the present and the past.\n<\/div>\n
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