What on Earth? New approaches for Earth observation in archaeology.

12 DECEMBER@14:30 - 16:00
Lidar scanning from a drone

What on Earth? New approaches for Earth observation in archaeology.

12 December 2023 @ 14:30 - 16:00
Lidar scanning performed with a multicopter UAV.  Creative commons licence.

 

New approaches for Earth observation in archaeology.

Professor Mark Horton (BBC’s Time Team, Time Flyers, Coast, etc)

Professor Mark Horton began by giving us a history of how aerial archaeology began. Earliest attempts involved using kites with an attached film-based camera that used servo motors to compensate for movement, but since one had to wait for the film to be developed before it was revealed that you had decent photographs, this technique was limited.

The earliest successful attempt at aerial photography was in 1906 when Lt Philip Sharp used a balloon to fly over Stonehenge and take photographs. The first World War gave a boost to aerial photography with the introduction of reconnaissance missions over enemy territory.

In 1928 O. G. S. Crawford and Alexander Keiller published Wessex from the Air – the first book of its kind with a reproduction of 50 photographic plates taken from the air of archaeological features in Hampshire, Wiltshire and Dorset.

Between 1945 – 1948 the first comprehensive aerial mapping of the UK was completed. Horton explained that aerial photographs were able to highlight humps and bumps, and he went on to explain about crop marks. Where a crop is growing on ground that has a stone wall beneath the surface the plants dry out quickly and do not grow well, whereas crops growing where there was a ditch beneath them grow better and greener because the roots have access to more water. This change in the amount of chlorophyl in crops was another way of identifying archaeological sites at certain times of the year. Crop marks work very well in the East of England where the crops tend to be mostly cereals but less well in the west of England where there is more arable land.

The National Mapping Programme from 1986 to 2001 used all the aerial photographs taken and brought them together with data from other sources to build a comprehensive archaeological map of human settlements.

LiDAR is a method for determining ranges by targeting the ground with a laser and measuring the time for the reflected light to return to the receiver. It has two advantages: firstly for creating a terrain model and secondly a surface model where the ground is covered by trees. LiDAR mapping has been done for most of England and pats of Wales and images can be seen here.

Drones were initially quite crude but new advances in 2010 with the use of GPS created a huge interest. Drones are mostly used to take photos and videos and are used quite extensively in filming. But drones have also been hugely useful in being able to create a 3D model of an area from hundreds of overlapping images.  Other sensors have been added to drones including LiDAR. The introduction of Normalised Difference Vegetation Index (NDVI) to drones has allowed new 3D models of buried buildings to be created by measuring the amount of chlorophyl in plants in a similar way to crop marks.

Horton showed us images from a whole range of different sites including Offa’s Dyke,  Salisbury plain and a Buddhist monastery in Outer Mongolia. He concluded by describing how Ukrainian forces are learning to use this technology to map bomb craters and potentially where mines are buried.

After the presentation we were treated to a live demonstration of a drone in action in Bridges car park. We were all impressed by how quickly it ascended and descended, and its ability to remain motionless in mid-air.

Charles Emes

 

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Details

Date:
12 December 2023
Time:
14:30 - 16:00
Event Category:

Venue

Bridges Centre
Drybridge Park
Monmouth, NP25 5AS
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Organiser

Cherry Lewis

Accessibility at Bridges Centre

Members’ monthly meetings are held at Bridges Community Centre, Drybridge Park. Some group meetings and activities also take place at Bridges. Off street parking is available here outside the building, and disabled parking is adjacent to the building entrance. There are no external steps or slopes, and the entrance doors are automatic. The ground floor is fully accessible and level throughout, and there is space for wheelchairs. There is a lift to the first floor, and accessible toilets on both floors. There is a hearing induction system in the Agincourt room where the monthly meetings are held.

Accessibility at Ty Price

Some group activities and meetings are held at Ty Price, St Thomas Community Hall, St Thomas’s Square. There is no off street parking here. The approach on foot is a gentle slope to double entrance doors. The ground floor of the building is fully accessible and there is a disabled toilet. The stairs to the first floor are wide and well-lit with a handrail on both sides, but there is no lift. There is a hearing induction system on the ground floor.