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Finding Forgotten Features - LiDAR in lockdown

Updated: Nov 22, 2020

Many of us will be looking for something worthwhile to help occupy our time during lockdown and here is a suggestion, which you might want to consider.

The National Library of Scotland is a great website, not only for free maps of the UK but also for easily accessible and useful LiDAR imaging.

LiDAR is an acronym for Light Detection and Ranging and is a method for measuring distances (ranging) by illuminating the target with laser light and measuring the reflection with a sensor. Differences in laser return times and wavelengths can then be used to make digital 3-D representations of the target.

It is a great tool for armchair archaeologists, enabling us to see what's hidden in the landscape in much, but not yet all, of the UK.

Locally, it has revealed hitherto unseen evidence of Medieval agricultural practice in the parish of Norton Disney.

This image shows that the trees of Hill Holt Wood mask an earlier landscape of Ridge & Furrow ploughing, cut by later features. This was most probably the domain of the Disney family, from where the village of Norton Disney gained its suffix. Of Norman French descent the Disney's enjoyed success as farmers from the late 13th century until the 16th century. They and their serfs have left a lasting mark on the Lincolnshire landscape.

The second image (source: Luttrell Psalter) shows the kind of plough used in the Medieval period. Its fixed moldboard, which turned the soil only in one direction, was repeatedly used on narrow strips of land, thereby creating the corrugations.

As well as exploring your own parish from the comfort of home you can seek out well known sites throughout the country and see them from a different perspective, as the image of the Avebury Henge illustrates.

Fancy a go at finding forgotten features (don't you just love alliteration)? Here's how to get started.

Follow this link:

1. From the screen, which appears, look for 'Side by side viewer' on the right hand side.

2. Click on that and the side by side screens appear with a 'Help' screen superimposed (just close the 'Help' screen by clicking on its X).

3. On the right side of the screen from the drop down box 'select a map series' choose LIDAR 1M DTM.

4. Then, on the left side of the screen from the drop down box 'select a map series' choose a map you want to explore

5. Navigate and zoom in and out of the chosen map to wherever you want to go on the left hand side and on the right side a matching LiDAR image appears (if it is available)

You may need to zoom in quite close to pick out detail but the map view more matches the LiDAR so you shouldn't get lost.

6. Any 'twin' images you want to keep can be saved as follows:

On a Windows PC press the Fn key and the PrtSc key (saves it to 'OneDrive')

On a Mac press Shift + Cmd + 3 (saves it to your desktop)

7. Once you have got the hang of it, try using and comparing results from all the LiDAR data sets listed. You will see that DTM (Digital Terrain Model) removes tree cover and buildings, whereas DSM (Digital Surface Model) keeps them in, as shown in the Avebury Henge image.

Well, that's it really.

Looking forward to hearing about and seeing what you discover.

Happy hunting!

Bob Garlant is a retired professional archaeologist. He is currently assisting with the planning of a fieldwalking project close to Norton Disney Roman Villa, part of 2 ½ year investigation at the site. Fundraising is also in progress to commission a geophysical survey and to carry out an excavation of potential prehistoric and Roman features already detected nearby.

Bob is also working on a ground-breaking scheme, championed by The School of Architecture, Design and Built Heritage at Nottingham Trent University, where photographs taken at ground level and by drone are processed, using sophisticated computer software, to create 3D images of historic landscapes and historic buildings and monuments, especially those thought to be at risk, with a view to adding them to the Historic Environment Record.

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