Τρίτη, 13 Σεπτεμβρίου 2011

Google Earth Archaeology

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By Henry Rothwell

According to one of Google Earth’s co-creators the inspiration for Google Earth originated with a description of a piece of software called Earth, which was instrumental to the plot of Neal Stephenson’s dystopian (but surprisingly fun) cyberpunk classic Snowcrash. In Stephenson’s novel Earth was a globe across which was tiled satellite imagery, maps, architectural designs and low level aerial photography. By ‘grabbing’ the globe and zooming in, the user could glean as much geographical information as they could wish for.

Another of its creators says it has its origins in the 1957 flip-book ‘Cosmic View’ by Kees Boeke. This was adapted into the ground breaking 1968 film ‘Powers of Ten’, in which the viewer is introduced to a quiet picnic scene on a Chicago lakeside, before being whisked away on a macroscopic journey into outer space, and then descending (via the pores on the hand of the picnicker) into the world of the sub-atomic particle. Regardless of the original inspiration (and it seems it’s a little of both) the software in its later incarnations contains enough elements of each to be an incredibly useful tool for anyone concerned with maps, terrain, and the manipulation of geospatial data.



Fig 01 – Lentil Soup

However that was not the case in its earlier incarnations, particularly for anyone with an interest in terrain which lay outside a major conurbation. In these rural areas, the experience of Google Earth could be replicated by holding ones face a few inches above a bowl of lentil soup. [Fig 1]

The big change came in 2007 when new, much higher resolution tile-sets were released. Where previously the rural landscape appeared to consist entirely of amorphous vegetal shades, the 2007 data release allowed hill forts, crop marks, henges, barrows, castles and a whole wealth of identifiable features to spring into comparatively crisp definition.

New levels of detail

This new level of detail coupled with the ability to overlay the image of a site plan more or less in situ made the limitations of traditional maps suddenly apparent. Try it for yourself – scan a site plan in to your computer or download one from the web. Open Google Earth and then click ‘Add Image Overlay’ on the toolbar, then, when the dialogue box opens, navigate your way to the relevant file. You’ll have to spend a little time adjusting the size of the image once it is imported, and for a really tight match, I recommend turning down the opacity so you can see the ground underneath the image. Once you’ve done that to your satisfaction have a good look. Are the field boundaries spot on? Is the OS map used as a base as accurate as you would assume? Is the north arrow as true as it can truly be? Apologies for these tedious and unforgivably impertinent questions, but the point is that experiments like the one above will prove even to the most sceptical user that Google Earth has made the transition from a novelty digital globe to a useful tool for archaeology.

Since 2010, users have been able to compare the latest tilesets with imagery taken in previous years – click on the clock icon in the toolbar and some parts of the country can be viewed as it was as far back as 1945 [Fig 2] , before deep ploughing wiped out vast amounts of UK archaeology [Fig 3]. It is hoped that similar coverage will be extended to the remainder of the country soon.



Fig 02 – Hambledon Hill – 1945



Fig 03 – Hambledon Hill – 2006

Though enthusiastic amateurs were amongst the first to adopt Google Earth and use it in an archaeological context, the academic world is increasingly coming to rely on the software, most notably outside the UK. A search for ‘Google Earth archaeology’ on the net will bring up a list of examples of research conducted from various desktops from around the world. And from these desktops, archaeologists have discovering that the bars to remote surveying have not just been lowered, but some have disappeared altogether. The initiall costs and hardships of reconnoitring geographically remote sites are bypassed at a stroke. National borders have been rendered insignificant – you are free to go about your business unrestrained by politics, both governmental and academic. The company of thrusting young men labouring under the belief that the recipe for a brighter future includes Kalashnikov rifles and a flagrant disregard of health and safety regulations can also be avoided effortlessly.



Fig 04 - Looting pits in Iraq viewed on Google Earth

Daniel Contreras is one such archaeologist. Contreras, a man with a deep interest in the relationship between human populations and the landscapes that support them, was inspired by a lecture given by Elizabeth Stone on the use of high definition commercial satellite imagery to assess the looting of archaeological sites in Iraq, both before and after the American lead invasion of 2003. Contreras decided to apply the same techniques to an area of Peru in which he had previously conducted a series of excavations. Unable to access up to date imagery for the project, Daniel instead used a mixture of images collected in 1945, and the tilesets from Google Earth. Looting pits were easily distinguished in both sets of images [Fig 4], and as a result he could plot the spread and increase of looting in the valley over distance and time (Contreras, 2009). Armed with such concrete evidence, Contreras then used the information to begin lobbying the relevant authorities to legislate against the worst excesses of the practice.

A new view

In Australia, Professor David Kennedy is studying the archaeology of Saudi Arabia, a country to which he cheerfully admits he has never travelled. Kennedy says that Saudi authorities simply don’t make aerial photographs available to most archaeologists, and that it’s all but impossible to fly over the nation to take your own, or perform a visual inspection. Kennedy turned to Google Earth and pored over a 1,240 kilometre area of territory, managing to rack up a total of 1977 potential archaeological sites. A large number of these (1082) were tear drop shaped funerary monuments, which were confirmed as man-made structures by a friend of Kennedy’s who lives in Saudi Arabia, and was happy to drive out to the required spot and take photographs for him. Until Google release the much anticipated ‘Dig Here’ plugin, it is likely that a pair of boots on the ground will always be the best way of confirming a find.

Professor Lee Berger, a South African palaeoanthropologist has managed to use Google Earth to help him and his team predict potential archaeological sites. Berger, of Witwatersrand University, initially employed the software to map the 130 odd known caves and 20 fossil deposits that he and his team were familiar with from the ground. By the end of this process they had become pretty good at recognising the tell-tale signatures displayed by these features. Once they knew what they were looking for, they managed to add 500 previously unrecorded sites to their map and, using this information, went on to discover two partial skeletons of a previously undiscovered species of Australopithcus – Australopithecus sediba, a potential human ancestor.

Google Earth and monument damage

Back in the UK, Google Earth is being used to discover new sites (often in the form of cropmarks) but there is also a pressing need to protect our known heritage. Illegal off-roaders have found Iron Age hillforts irresistible, and have been merrily chewing them up for their entertainment. The remains of a Bronze Age Village near Barry Island in Wales which narrowly avoided being obliterated by dockyard development in the 1940s is now being rapidly eroded by scramblers and off-roaders. [Figs 5 & 6] Though technically they are not allowed to do this, they can hardly be blamed – the site is on seemingly abandoned wasteland pockmarked with puddles and nothing has been done to dissuade them from riding their bikes over it. Neither is there anything to suggest that a potentially valuable archaeological site exists there. So although in the second case there is at least the excuse of ignorance to fall back on, the damage caused to Somerset’s Priddy Circles can raise no such mitigating circumstances – a quarter of the southernmost Circle has been bulldozed out of existence. [Fig 7] Heartbreakingly, aside from an excavation in the 70s and the more recent sterling work by Jodie Lewis and David Mullins, very little archaeological investigation has taken place at the Circles, and there must be a great deal of data which is now unrecoverable.



Fig 05 – Bronze Age site near Barry Island - 2001



Fig 06 – Bronze Age site near Barry Island - 2006



Fig 7 Images of the southern circle in 2003 and 2011. Photographs by Pete Glastonbury

And though the situation at Priddy Circles has caught the imagination of the public it would be wise not to become too distracted by the more obvious examples. It would instead be more constructive to put some energy into making sure that the destruction of heritage will have serious consequences.

The UK archaeological community could do a lot worse than follow the example of Daniel Contreras and start using Google Earth as a tool for monitoring the degradation of our heritage, with the aim of lobbying for effective prosecution in mind. Begin with your local patch, or a favourite monument/site. Check in now and again and see if there is any new imagery for the area – look closely – can you see any differences?

If you think you can see something untoward occurring there are a number of Facebook groups you can get in touch with, and of course RESCUE– the British Archaeological Trust.




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