Friday, 18 September 2015

#Familiarise Friday meets LiDar Surveying

My #Familiarise Friday slot is quite different today.

LiDar Surveying used by archaeologists is still relatively rare in Scotland but I was fortunate to go to a talk last night by Gordon Noble at the Bailies of Bennachie AGM in Inverurie, north-east Scotland. I now know what great potential such surveying has—though it still needs the methodical archaeological hand and footwork on the ground to 'prove' what appears in the high definition 3D imaging.

I had thought LiDar to be a newish technique but found out it has been around since the 1960s, though not used in the archaeological sense at that time. In the 1960s, LiDar was developed to detect submarines from aircraft.

Today, a LiDar system would generally consist of a LiDar sensor, a GPS receiver, onboard computer and data collection systems - sometimes with an IMU inertia measurement unit as well. A very simplified version of the technique would be that a laser beam is pulsed onto a mirror and projected downwards to the ground, the mirror generally on a fixed wing of an aircraft- aeroplane or helicopter. As the aircraft flies over the area to be surveyed, the beam scans from side to side so quickly I can’t really relate to—some 20 thousand to 150 thousand points per second. When the beam hits an object on the ground it is reflected back to the mirror. The resulting data is processed and a high resolution 3D map/model of the surveyed area can be made.  

This site HERE has a more complex explanation. 

LiDar wasn’t used in the 1976 survey the north-east of Scotland but regular aerial imagery/photography was. At the time, the more simple aerial photography produced some fantastic new evidence for ancient forts and enclosures. The summers leading up to 1976 had been particularly dry in the area and it was as a result of this that crop marking seen in the aerial surveying was so successful in 1976 for identifying ancient uses of the land.

This was great news for me in my current field of study because it highlighted more about the Roman temporary camps than had been detected by archaeologist on the ground, prior to the surveying of north-east Scotland in 1976. taken 1976
One of the faint lines in the image above isn't a field area marker, but is the line of the ditch/rampart of the Roman Marching Camp at Deer's Den, Kintore. Just above the first 'h' of the URL for the Canmore site ( my thanks to Canmore ) is the south western corner of the very large 44 hectare Roman temporary camp.

The difference between the above type of regular aerial photography and LiDar surveying is that LiDar beams can show what has been ‘happening’ almost everywhere on the ground surveyed. Even in dense forestry areas it indicates where earth has been disturbed because the LIDar ‘blocks out’ any buildings or structures of some height. To be able to detect ancient uses of land UNDER forestry areas is amazing and the potential therefore, I believe, has to be higher for the archaeologist studying such areas.

I can't provide an image yet on this blog (Copyright restrictions)  but HERE is a site where you can see more of the archaeological use of LiDar,

Cost is always a factor in any archaeological surveying, but if that could be organised there might be a wealth of information which could be uncovered, details which will make us understand much better how the people lived hundreds, and even thousands, of years ago.

The implications for me as an author is that I'll be keenly watching out for more information on the local LiDar survey results. So far, Gordon Noble and his team have identified structures (hillforts)  in the Rhynie area as being post Roman era in north east Scotland of 5th/6th century AD. Since I'm presently more interested in the period of 1st to 3rd centuries AD, I'm eagerly awaiting knowledge from any further LiDar surveying of northeast Scotland which might provide new information on the late Iron Age eras.

I'm always happy to re-write parts of the draft of book 4 of my Celtic Fervour Series should anything interesting crop up!


No comments:

Post a Comment

Thank you for reading my blog. Please pop your thoughts about this post in the comment box. :-)