LiDAR investigations of the Kent landscape

My interest in LiDAR started at the beginning of lockdown. I’ve always been fascinated with anything to do with archaeology, but as my career was in broadcast motion graphics, I wondered if I could combine the two disciplines.

I did some initial research after reading about the surveys made by DEFRA in the UK via their freely available LiDAR datasets and began my search.

TECHNICAL BIT

The downloadable “tiles” on DEFRA are logarithmic 32-bit TIFF images and need to be processed in Photoshop to make them viewable in 3D software. When you have done this, you can then use this greyscale image to distort a 3D mesh to “extrude” upwards and downwards based on the luminance values of the image (dark is low, white is high), thus revealing many interesting surface features in the landscape.

BACKGROUND

As I grew up in Norfolk, I first looked across the coast to see if I could find anything of interest and then, if I did see anything, I cross-referenced it with the Historic Environment Record (HER) map of that area to see if it had already been listed. This is when I came across Warham Camp by accident, which I never even knew existed, and which is huge (for Norfolk) and only up the road from where I grew up. This well-known Iron Age site became my reference Iron Age site for image interpretation whilst searching for unknown hillforts across the UK.

Fast-forward a year and I got in touch with Gary Lock (Oxford University) and Ian Ralston (Edinburgh University), who wrote the definitive guide The Atlas of Hillforts. This helped me understand what to look out for when discovering ancient hillforts across the landscape. I chose Iron Age hillforts as a focus because they are very large, have obvious morphological characteristics such as rock-cut banks and ditches—usually in rows surrounding the habitation area—and they are still being discovered.

[fg]jpg|Fig. 1 – Richborough Castle, Kent (oblique).|Image[/fg]

[fg]jpg|Fig. 2 – Homestall and Bigbury Camp, Kent.|Image[/fg]

I started to post my 3D-generated images on various websites and forums, as I wanted to support Gary and Ian’s work by visualising sites with LiDAR instead of aerial photography. Many hillforts in the UK are completely covered in foliage and trees and are not obvious from the ground or the air. Since lockdown, they now support their own database with web-based LiDAR imagery. I hope I gave them some inspiration.

MORE SCIENCE

LiDAR (Laser Detection and Ranging) data is produced by firing a laser from orbit or a plane or drone at the ground and measuring the return reflection to generate a measurement point. The return signal can be processed in various ways: if it shows a specific “wiggle” in the return beam (for want of a better word), it has probably passed through foliage and can be discounted if required. The same applies to modern buildings, which can be “removed” using an algorithm linked to a building database.

The resulting data is called a Digital Terrain Model (DTM). If the foliage signal is left in the data, it becomes a Digital Surface Model (DSM). I work with DTM data, as I don’t need to see trees in my images.

NEW DISCOVERIES

I started to work my way around different counties of the UK, imaging hillforts already listed in the Atlas of Hillforts. When I reached Kent, I noticed something encircling part of a hill that looked like an Iron Age site. After checking the Historic Environment Record map and finding nothing listed, I sent my findings to the Kent HER. Dr Rose Bradley (HER Record Officer) later confirmed that a site visit had taken place and that it was indeed an unknown Iron Age site.

“I circulated your query to our team, and one of my colleagues managed to visit the site. He suggested that the enclosure may be the result of a more temporary camp rather than a ‘hill fort’ per se, but that it is worth listing on the HER, so I will add it to our list.”

[fg]jpg|Fig. 3 – Homestall Camp, Kent (oblique).|Image[/fg]

[fg]jpg|Fig. 4 – Oldbury Camp, Kent.|Image[/fg]

[fg]jpg|Fig. 5 – Perry Wood, Kent.|Image[/fg]

I was over the moon and began looking further afield on the LiDAR data whenever I imaged a site, seeking out more unlisted hillforts. I now have over 50 newly discovered sites added to various HER territories across the UK. Most are in Wales, where access to a single 50 GB 32-bit GeoTIFF LiDAR file allowed me to work efficiently using QGIS Desktop to export imagery for 3D visualisation.

Working with Dr Ken Murphy (now retired) and Dr Toby Driver, they helped analyse my findings and confirm positive discoveries. In one memorable email they explained that I had not discovered an unknown Roman road, but rather rediscovered a massive Welsh gas main running across the landscape.

Later, I discovered an unrecorded cluster of burial mounds in Carmarthenshire. Dr Ken Murphy visited the site himself and tentatively confirmed the findings, although an evaluation trench will be needed to confirm their provenance. Some of these mounds are larger than Sutton Hoo and lie close to a sea inlet, making the discovery particularly exciting.

[fg]jpg|Fig. 6 – Holly Hill Wood, Kent.|Image[/fg]

[fg]jpg|Fig. 7 – Stutfall Castle, Kent (oblique).|Image[/fg]

[fg]jpg|Fig. 8 – Squerryes Park hillfort, Kent (oblique).|Image[/fg]

[fg]jpg|Fig. 9 – Unlisted site near Squerryes Park hillfort, Kent.|Image[/fg]

My first Kent discovery was the Holly Hill Wood site near Snodland in 2022, when the HER sent a crew to evaluate and confirm the hillfort. After moving to the Isle of Sheppey, I investigated the island and found many interesting features. I have also identified a possible Iron Age site northeast of Squerryes Park hillfort, which Kent County Council have included in their records for future evaluation.

Since then, I have made several more Kent discoveries, which is remarkable given how extensively the county has already been surveyed. I continue to update the KAS whenever I hear back from Kent’s HER office.

Next, I plan to launch a dedicated YouTube channel to fully reveal my LiDAR discoveries, supported by drone fly-arounds, LiDAR interpretation tutorials, and showcases of sites best seen through LiDAR imagery.

If you would like to see more LiDAR images from Kent and across the UK, or contact Simon, please visit:

Website: www.ukhillfortlidar.myportfolio.com
Instagram: @mrtedgfx
Motion graphics work: www.threedimensionalcube.com

Simon Terrey is a broadcast 2D and 3D motion graphics designer in London since 2003. Between 2006 and 2012 he was Head of Graphics at two television production companies and is currently freelance as a Senior Motion Graphics Designer.

[fg]jpg|Fig. 10 – Lees Court Estate, Kent (LiDAR composite).|Image[/fg]

[fg]jpg|Fig. 11 – Isle of Sheppey, Kent (wide).|Image[/fg]

[fg]jpg|Fig. 12 – Isle of Sheppey, Kent (grid pattern).|Image[/fg]

All images courtesy of Simon Terrey, permissions obtained, 2025.