23 Nov 2007

Airbourne lidar opportunity for Randwick?

Airborne LIDAR - well I have to confess I'd never heard of it until the beginning of this week - Light Detection And Ranging - it measures the height of the ground surface and other features in large areas of landscape with a resolution and accuracy hitherto unavailable, except through labour-intensive field survey or photogrammetry.

Photo: comparing lidar and google on computer and below closer detail of lidar

It provides highly detailed and accurate models of the land surface at metre and sub-metre resolution - operating by using a pulsed laser beam which is scanned from side to side as the aircraft flies over the survey area, measuring between 20,000 to 100,000 points per second to build an accurate, high resolution model of the ground and the features upon it.

The Parish of Cranham have a project to survey a large area (costing many thousands of £££) and for a mere £2,500 extra they would consider Randwick and Standish area. One parishioner attended the talk at Cranham this week and was impressed by the incredible detail and versatility of this stuff - 'stuff' - oh dear my descriptive powers are failing me this evening - anyhow he contacted me and he kindly invited me to view LIDAR in action on his own computer yesterday.

It was certainly impressive giving vertical resolutions of only a few centimetres - perfect for a vast range of projects - particularly archaelogical research and flood modeling. One map showed the site of an old triangular Roman fort - particularly interesting as the road it was on has always been known locally as the Roman Road - it also showed at another site that instead of three separate forts there was only one - indeed it was leading to a rewriting of archaeology for that area!

It would be very wonderful to do the same here - particularly looking at the ancient sites in the local woods (see previous blogs re barrows). Plus it could be used for a multitude of other purposes - flood modeling to mapping toxic fumes from a possible explosion at a plant and much more.

I have since spoken with Parish councillors and also officers at the District Council - they had a very helpful guy there who was a mapping expert - I learnt that LIDAR data was used by the EA as part of the detailed planning for the canal line. However the District Council take height data from a company called Intermap - not as detailed as the LIDAR data and wouldn't be suitable for detailed analysis such as the very detailed flow modelling and archaeological applications. SDC have however used it for 3D visualisation purposes (e.g. for the Brimscombe AAP) and for planning applications relating to masts and turbines. In these planning cases they create a 'viewshed' - a layer that shows all areas of land that the structure can be seen from.

So where are we - well the cost - it's very expensive - SDCs aerial photography for Stroud District was about the same price as quoted above for Randwick parish - but then this is something quite different. The stuff (oh dear there I go again with my descriptive powers) takes up huge amounts of disk space to store (because of the detailed resolution) - and apparently software applications that handle LIDAR are expensive and need to be used in conjunction with very high powered computers.

Is there anyone in the Parish interested in taking this forward? The Parish Council members I have spoken to are interested - so are the local Historical Society - but I doubt they can proceed when we are talking £2,500 - then of course we need a group to follow up to analyse the stuff (OK last time I mention stuff) whether it be archaeological or flooding or whatever if we are to proceed we need to act quickly as surveying must start in new year when no tree cover.

Further resources:
LIDAR general - go to:
http://en.wikipedia.org/wiki/LIDAR
LIDAR Archaeological Applications - click here.

2 comments:

Anonymous said...

would the university of gloucestershire help contribute towards the cost in relation to any future projects they have in mind for the geography and environmental dept. suggest possible contact Bob Moore. He deals with gheographical information systems and remote sensing.

Philip Booth said...

Sounds a good idea - although I suspect Universities don't have much spare cash - has anyone got time to pursue? It would be great to get students looking at the area from various angles.