Thursday, 28 March 2013

Neroche

The Neroche Landscape Partnership Scheme covers the Northern area of the Blackdown Hills, in Somerset. They recently had some LIDAR work done to help understand the archaeology of the area. (LIDAR is explained in the way in which I understand it, at the bottom)

I was kindly asked to produce a few illustrations to help furnish a toolkit to aid with "ground truthing" (my spellchecker wants me to say trotting, which I think I prefer!) the LIDAR. Images to help visualise what we might be looking at, or looking for, given the clues from the LIDAR.

Here we have an Iron Age Hillfort, a flattened platform atop a steep sided hill, rimmed by a bank with a palisade and a ditch. Cutaway in the corner is an example of a double ditch and bank.

From the air this seems a pretty defined structure but it is a little hard to appreciate from the ground, here are a couple of pictures I took of hill forts while down in Dorset, last year.

Pilsdon Pen, not much to see from this angle, looking uphill some way below the fortifications.

Here at the summit, it is like an open field whose edge is the horizon. This view really benefits from the lack of trees and scrub at the top, as you can see some collapsed earthworks around the fringes.

This final picture was taken at Coney's Castle. You can see what an impressive feature the bank is, considering especially that it runs all the way around, along the contour of the hill. However, you can only see a small part at any one time as it forever curves around on itself.
LIDAR helps discover archaeology by shooting lasers from the sky, that's all anyone really needs to know.

LIDAR is a technique used to scan the landscape from an aeroplane, flying back and forth across a large area, to create maps devoid of trees and other ephemeral obstructions which allow us to see the underlying detail of the land; trackways, streams, barrows, many features small and large, but normally obscured. Basically, lasers are shone from the aeroplane and the returning beams are interpreted as as 3D point-cloud.

If you flew over a field with a tree in the centre, the point-cloud would look like a big flat sheet made of dots, with a group of higher dots in the centre. So, things like trees can be defined as areas where the points jump up suddenly in concentrated areas. Filtering these spikes from rest of the information and covering the dots with a skin, gives you something resembling what the ground looks like underneath, have a look!