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Lidar surveys
#1
What is the consensus out there regarding Lidar surveys? Do they really see through trees - what about dense rhododendrons and bracken? All the websites say so, but are they right...

Has anyone out there had a good experience of using this tool in a commercial environment? A likely use, I suppose, would be a walkover survey for a DBA/EIA, where the ground cover in woodland or heathy country was too dense to see low earthworks.
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#2
I too have seen some fantastic results from LIDAR, but it has to emphasised that LIDAR does not take photographs, it records data and the way the data is manipulated is what produces the result (for comparison imagine what a Time Team geo-fizz survey looks like in reality and then once it has been 'filtered' for presentation to the viewing public).

For an explanation of how this works I have found this link, which explains fairly concisely how a team from Leicester I think, used LIDAR to strip away a heavily forested Balkan hillside to discover the bedrock below. Depending on the algorithm used I guess you could strip away or leave behind any amount of 'ground cover'.


http://www.le.ac.uk/geography/research/p...LiDAR.html
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#3
Not quite an answer to your question really, but I have seen good results from Lidar in open countryside areas. It was a good supplement to aerial photos and geophysics. The key thing was that it picked up not only prehistoric archaeolical features but also 'fossil' natural landscape features that would otherwise have been undetected over large areas, and that were crucial to the archaeological interpretation.

1man1desk

to let, fully furnished
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#4
There seem to have been some good results in the Mendips AONB survey in wooded areas, on the EH website at http://www.english-heritage.org.uk/server/show/nav.8730

Cheers,

Brian
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#5
I have also met people who claim that lidar readings of areas around goal mouths on football pitches are actually Roman villas when they are clearly just goal keeper spread and similar.
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#6
I was involved on a project where we used LiDAR as a tool to record upstanding ridge and furrow along the route of a gas pipeline. Usually there is a problem with getting access to the area beyond the easement but with LiDAR we were able to get data on the entire field and beyond. The fine detail may not have been as accurate as a field survey but as a way of placing your site in a wider context it was certainly an improvement and a bonus for the local SMR.

Word of caution however - some of the EA data we used was a bit iffy in places and some fields where we could clearly see well preserved R&F were not evident on the images. Overall though I was quite impressed and would consider using it again, albeit backed up with field visits where possible.

It did assist in the identification and/or interpretation of a nos. of earthworks which would not have been identified or understood from the narrow confines of the pipeline easement.
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#7
LiDAR is a useful additional tool alongside HER, cartographic evidence and AP evidence. Excellent for palaeochannels. Good for subtle earthwork features which you might need optimum conditions to see in the field, if at all. Piles of building rubble dumped by farmers can make themselves into interesting cairns though! As ever, a tool to be used as part of a suite of techniques.
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#8
I *love* LIDAR! I've used it quite a bit here in Canada, it is especially useful for projects in the northern boreal forest. It's like the trees aren't even there! ArcGIS can even create some snazzy DEMs from LIDAR data, not the best source but it's the best I've had access to.
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