Stonehenge

Two exciting pieces of research affecting Stonehenge have been pointed out to me and are too good not to pass on.  The English Heritage funded 3D Stonehenge model has used high resolution terrestrial laser scanning to produced an unparalleled, accurate three-dimensional model of the stones.

Meanwhile, at Bournemouth University the team responsible for one of the recent campaigns of fieldwork at Stonehenge have completed the Google Under the Earth: Seeing-beneath-Stonehenge project. Funded by the Google Research Program. Birmingham Postgraduate Lawrence Shaw has worked on this project and blogs about it here.

Great work, and nice visualization in both cases.

The Scottish Ten

More from Technological Advances in Landscape and Heritage Management Recording.  The Scottish Ten is another fine example of a terrestrial laser scanning project of epic and imaginative scale producing beautifully visualized results.  In its own words "A groundbreaking international 3D scanning project to digitally document Scotland’s five World Heritage Sites and five international ones".  Work has employed a variety of scanning techniques to document sites as diverse as St Kilda, Neolithic Orkney and Mount Rushmore.

I'm particularly taken by the effectiveness of their translation of laser scanning from point cloud to photo-realistic models (viz the movie above) and crave more information on their methodology.  The impressive pre-rendered visualizations are a great example of what laser scanning is capable of - but I'd love to see the same data ported to a game-engine for real-time interactive exploration.

The City Beneath

As promised something on Dave Walker's Nottingham Cave Survey that so impressed me at Technological Advances in Landscape and Heritage Management Recording in Dublin last Friday.  Dave and his team have been working on producing a comprehensive digital record of Nottingham's unique and relatively little known systems of man-made rock cut caves, the earliest survivors of which date to the Middle Ages, but for which there are far earlier accounts.

Using a variety of terrestrial laser scanning kit the team have worked on the "cave a day" principle to produce a stunning primary record.  While there is little in time and resources to make too much of these data what Dave has done is produce some lovely, quite ethereal flythroughs using Pointools View Pro.  Nottingham is my home city, and I've wandered through a few of the caves over the years; these visualizations perfectly capture the sense of strangeness that descent from sunlit city street to subterranean space creates - I'm always reminded of something faintly Lovecraftian "the catacombs of Ptolemais, and the carven mausolea of the nightmare countries" but that's just me...

Technological Advances in Landscape and Heritage Management Recording

Here, for the record, my presentation given at Technological Advances in Landscape and Heritage Management Recording in Dublin on Friday.  An excellent, useful and enjoyable day with some very interesting presentations, particularly focused on high resolution airborne and terrestrial lidar.  I was really taken by the work of Dr Dave Walker on the Nottingham caves (good enough to deserve its own post, so more later) and the Scottish Ten, mysterious name, but great work, again deserving its own post. Since I managed to give the wrong version of my presentation, anyone interested in what I had to say will get a fuller picture from the below...  

Visualising Terrestrial Laser Scanning

The idea of pointing a terrestrial laser scanner at the ground, rather than at some sort of building or structure, may not be entirely new, but the question remains what to do with the huge quantities of data such idiocy generates.

The data visualised here is of the north-eastern entrance of the Iron Age hillfort at British Camp, Little Malvern and was collected as part of the coursework of one of our postgraduate students taking the MA programme in Landscape Archaeology, GIS and Virtual Environments.  He used a Leica HDS3000 TLS, hauled to the top of the hill twice (it failed to work the first time) and collected 3.2 million xyz data points from three survey stations.  The point data was stitched together in Leica Cyclone, but then, what?

Effective data exploration was undertaken in the hugely capable Quick Terrain Modeler (usually used for airborne lidar data), but decimating the data to allow visualisation in ArcGIS and ArcScene produced disappointing results. Here are the same data visualised using CryEngine 2 and a little imagination.

Fair I think to say that the metrical accuracy of the CryEngine model is way below that of ArcGIS or QT Modeler.  X-Y co-ordinates are fine, although limited to 1m spatial resolution, somewhat below the centimetre level of the original data. The principal problem with CryEngine is the Z scaling, limited to a range of 256 increments from lowest to highest value (that is the 256 shades of grey possible in an 8-bit heightmap).  At British camp the vertical range in the original data is 90m, so in our CryEngine  model each heightmap increment is equal to 35cm with the inevitable compromise in resolution.

Nonetheless, the dressed terrain model, with texture, vegetation and effects, is a pleasing, interactive rendering of the landscape which capture the original more effectively that the metrically correct, but dry 2D visualisations.

So what is going on here?  For my money, these lower resolution game-based visualisations more truely present landscape in the way our brains cognitively interact with the world around us.  We don't see millions of data points, we see impressions of landscape, tussocky grass, the fleeting movement of birds and the interplay of light and shadow on the land.  So, feed the mind with familiar fare and happy sensory engagement results.  And what of those lost millions of points?  Still there in the ether for analysis if needed...