Sunday, 10 November 2013

Archaeological Techniques for the 21st century

There have been a huge range of developments in technology in the last few years; ipods, then iphones; free software that you can use on your laptop; cheap cameras and dvd players, etc. etc. This has some interesting side effects for commercial and academic archaeology (mostly because as you produce more of something, generally the cheaper it gets), but here are a few things you may not have heard of that are finding uses in archaeology (apologies, this is a long post!):

RTI (not to be confused with Real Time Information, a system of Pay as You Earn in the UK!)

Reflective (or reflectance) Transformative Imaging (RTI) is a relatively new technique that involves a camera (ideally high resolution), a few bits of kit and a PC with the right software installed. The idea is that 2-dimensional surfaces are deceitful; they are often made up of grooves, holes and other depressions which have been created either by nature or by man. You can tell the difference usually because the man made grooves look, well, man made. More often they are following a known human pattern (see image 1 below). Conventional camera-taking techniques don't capture these depressions on their own. But, you can take multiple images of one 2-dimensional surface from different angles, and with the help of processing software, you can see these depressions! It can't work without the software, because the software can work out the mathematical calculations involved in finding these depressions, creating a 3-dimensional image; this is not something that you can just do right now with your own camera (unless you buy/borrow the kit!). See here for more information on the technique. 


This is a particularly good technique, not just for the potential to reveal new information about a painting or a wall carving (i.e. the paint might have gone away but the traces can still be found by this technique), but also as a good way of digitally storing the information about these objects; by forcing the archaeologists to take more photos! This technique can be used on any surface, such as coins. If you can photograph it, you can RTI it!


Image 1: Normal image in bottom left, after RTI processing on the top right. Note how here the grooves tend to follow the painting (Cultural Heritage Imaging).


There are some drawbacks however. The kit itself is a little pricey (at $350) and there is only one manufacturer of the equipment (based in the USA). And currently it's main use has been limited to California in the USA. But, Southampton University and Oxford University have been pioneering its use in the UK, in one case in churches, in collaboration with local archaeological groups (). The software itself (called RTIbuilder) is now free to download.

surface normals diagram 1
rti diagram 2
Image 2: Above is the direction light normally travels when captured from one angle. The bottom image shows how multiple angles can "capture" the effect of the grooves etc., simply because the software knows where the light source is coming from, and where the picture is being taken from. Magic! (Cultural heritage Imaging) 

There are a number of blogs now dedicated to the advancement of RTI (mostly American); see here for an example of a discussion of which is the best camera to use in RTI.


Motion-Capture (with thanks to Jasmine Noble-Shelley for this one!)

The use of motion-capture technology in archaeology is rare, but not unheard of. It has been used in museums for a number of applications, such as in the Louvre, and the Roskilde museum in Denmark. In Britain, Jasmine Noble-Shelley pioneered the use of an Xbox Kinect to create a "virtual excavation" using nothing more than some cameras, a sandpit and some willing volunteers (Noble-Shelley 2013)! This allows the volunteers to engage much more with an actual site than they could normally, especially if the site in question is able to attract the public's imagination, such as Pompeii or Tutukhamun's tomb (Noble-Shelley 2013). Some of the software that was used in a particular geological project is openware (i.e. free to download) and can be found here.

Both of these sites are now under threat from the sheer weight of visitor numbers. So this could also be the way forward for allowing people to visit "real" sites by creating 3-dimensional ones that can be explored using motion-capture devices, without actualy visiting them!

Ipads (with thanks to Craig-Lee Holt for this one! Saw your facebook post about this topic a while back)

Going from Microsoft to Apple, who would have thought that Ipads would have a direct application in the field of archaeology? In Britain and the USA at least, they have found their way onto commercial excavations, saving time and money by allowing archaeologists to record the archaeology directly into a database, rather than using paper formats, then copying it out later into a database. Sounds simple, doesn't it? But imagine trying to lug a computer or even a laptop around a muddy excavation to do the same task as the Ipad! Also see here for an academic project in Palestine that is


Laser scanning techniques

Lasers have come a long way from being just fancy light displays! In addition to laser printers, now you can use lasers to create 3 dimensional images of monuments! In Britain, by far the most famous example of this technique is Stonehenge. But did you know that there are multiple ways of applying lasers to record archaeology?


  • Triangulating 3-D scanners
    • This technique simply uses the principle of triangulation (not dissimilar to RTI above), by placing a digital camera at a different angle to the laser, the 3-dimensional component of the image can be worked out. This leads to a very high resolution (quality) and accuracy of the surface (Laser Scanning Stonehenge/Archaeoptics 2003). This was the technique applied to Stonehenge a few years ago, and is better suited to a more abstract 3-dimensional surface.
  • Time of Flight 3-D scanners
    • This technique differs because it's principles are borrowed from Sonar: send out a laser and measure the time taken for the laser to return. So a laser scannign  device can be set up to move up and down to scan a surface. Hence, a 2-dimensional surface can be recorded quite easily with this technique, although it is not quite as high-resolution and high-quality as the triangulation method (Laser scanning Stonehenge/archaeoptics 2003).
  • CT (computer tomography) scan
    • A comparative newcomer to the game, coming from a medical background, which in itself is an unusual route. But it provides an excellent, high-quality scanning procedure that can capture the tiniest of details. The vast majority of CT scans have been used on mummies thus far (Hughes 2011), but it has also been used recently on the Hilton of Cadboll cross in Scotland, which stood about over 5m tall but is now in over 3,000 pieces(National Museums Scotland)! You can get involved in reconstructing the cross  here.
  • LIDAR (Light detection and ranging)
    • All of the above techniques are great for individual artefacts and monuments, but what if we want a (quite literal) bigger picture? LIDAR has come into it's own in recent years, although it was also being used in the 1960's for submarines. Usually taken from a plane, this technique involves the same principles as Time of Flight, but it can take 10,000's of points per second! It has been used to map areas of land from smalls fields right up to county level and beyond (English Heritage)!


GIS

Geographical Information Systems (GIS) have been around since the 60's, with the first archaeological application in the 1970's. It then fell out of favour during the 1980's, but has made quite a comeback since the 1990's (Wheatley and Gillings 2002), to such an extent that the chances are that any archaeological project today will make some use of it, even if it is just to create a map. GIS describes a software package that deals in geographical spatial information, mainly in map form. But, it also allows you to create spatial data, either in relation to other layers or on it's own, analyse the data, and even start to predict where sites can be found (amongst other things)! However, this requires a lot of computing power, even for a "basic" GIS, so make sure you have a powerful laptop if you are going to try these at home.


There is free software for GIS that you can simply put onto your laptop for free, such as GRASS (at the time of writing, the latest version was 6.4.3). An alternative that has been developed exclusively without archaeology in mind, but can still be used, is CorelDRAW. It is pretty old now, I'm not entirely sure if you can get it online for free, but it's worth a look to see similarities between other packages.

The major disadvantage (aside from computing power and storage) is top-down approach of most GIS programs; very few explicitly model the individual human's activities, whether they are in the past or the present. Therefore it is better to use GIS as a large map that is used for sweeping statements about the past landscape, than for trying to model one person's actions within a particular environment.

Graphics Software

Graphics software is becoming more and more accessible to all disciplines. Again, more free software is available from many places. In archaeology, it can be used on a variety of topics, from displaying unique symbols on a map to putting the finishing touches to a report.


Geophysics


Geophysics has become a mainstay of archaeological research these days; even 20 years ago it was a popular (albeit relatively more expensive) technique. There are 3 main kinds of geophysics (although there are some other types, see above for LIDAR, which is strictly speaking a geophysical technique):

  • Magnetometry; generally the most popular of the techniques, it is the cheapest and the fastest. It relies on taking readings of the magnetic field of objects in the ground, but also the background magnetic field. By doing some clever math, it can try to work out how strong the magnetic field is from the archaeological objects in the ground! There are a small variety of different types of magnetometers, each essentially serving the same purpose However, it is an extremely sensitive object; you can't wear metallic objects, or pass under telegraph poles with magnetometers (don't even think of going near fences!), because the magnetic field is so strong, that the machine simply can't make out what's underneath the soil. Also not advised to use when there is a solar flare happening in space that is heading towards earth.
  • Resistivity; Much slower than magnetometry, but no less useful, this machine puts electromagnetic probes into the surface, generates a small electric current, and two more static probes recieve the signal. It detects the electrical resistance of objects under the ground, although the effectiveness of the technique varies depending on the water content of the soil (needs a little to be good), and the distance between the two sets of probes. I found the foundations o a church once using tresistivity! The slowness of the technique means that magnetometry is often preferred when there is little time to survey a large area.
  • Ground Penetrating Radar(GPR); the last technique relies on radar to create "time-slices", or layers, of what is underneath the ground. It is the slowest technique by far, and the most expensive, but the quality of the results often outweigh the negatives in a small area. nklike the other two methods, there are very few background conditions that have to be met.

Google Earth

Google Earth has found its way into a number of archaeological projects and reports, with it's total view of the earth, and now a new "time-depth" feature, which allows you to access aerial photographs from the past, particularly in Britain for just after World War 2 and into the early 20th century in some cases! With the height of the earth also computed, it allows you to make sweeping generalisations of the landscape very quickly, as well as seeing aerial photographs for free, when before you would have to visit certain institutions, like the Cambridge University Collection of Aerial Photography, and then pay to have copies of the photographs.

However, there are a number of issues with using Google Earth for Archaeology. We have no idea where Google Earth are getting these images from. Well, we know they are coming from declassified military information and civilian sources, but Google's not going to tell us which is which. Furthermore, Google Earth won't tell us the resolution of the images; if we don't know the resolution, then we can't compare it to other images that archaeologists have taken on higher (or lower) quality cameras. Finally, you will notice that the quality of the images across Google Earth is far from uniform, so some places will have some half-decent images, but other areas less so, which can affect a comparative study in archaeology. Also it is quite tricky to georeference a Google Earth image to a GIS software package. So use with caution, although it is still a free and powerful tool, which can be downloaded for free here


So that's my list of things that are becoming more and more popular in the 21st century, as well as things that have been introduced over the last 10 years or so. This situation will continue to develop, maybe some of these technologies will fall out of fashion, others will set the standard for future technologies to follow. This is not an exhaustive list by any means, if you have any suggestions about other new archaeological techniques please comment below!


References:

National Museums Scotland, last updated unknown, Pictish Puzzle, http://www.nms.ac.uk/collections__research/glenmorangie_research_project/pictish_puzzle.aspx, last accessed 31/10/2013

English Heritage, last updated 2010, LIDAR, http://www.english-heritage.org.uk/professional/research/landscapes-and-areas/aerial-survey/archaeology/lidar/ last accessed 31/10/2013

Hughes, S., 2011, CT Scanning in Archaeology, in Computed Tomography - Special Applications, Dr. Luca Saba (Ed.),published by InTech, Available from: http://www.intechopen.com/books/computedtomography-special-applications/ct-scanning-in-archaeology

Laser scanning Stonehenge/Archaeoptics, last updated 2003, 3D laser scanning,  http://www.stonehengelaserscan.org/laser.html, last accessed 31/10/2013

Noble-Shelley, J., 2013, The Kinect: Potential and Application within Archaeological Education and Outreach, undergraduate dissertation, University of Southampton

Wheatley, D and Gillings, M., 2002, Spatial Technology and Archaeology: The Archaeological Applications of GIS, Taylor and Francis, London



Appendix:

Image one: Cultural Heritage Imaging, last updated unknown, Reflectance Transformative Imaging (RTI)http://culturalheritageimaging.org/Technologies/RTI/The Sennedjem Lintel from the Phoebe A. Hearst Museum of Anthropology at the University of California, Berkeley.
RTI representation showing color information (bottom portion) and “specular enhancement” mode showing surface shape and enhanced reflectance (top portion), last visited 10/11/2013

Image two: Cultural Heritage Imaging, last updated unknown, Reflectance Transformative Imaging (RTI)http://culturalheritageimaging.org/Technologies/RTI/, Figure 2, last visited 10/11/2013

Links:

Link 1:Cultural Heritage Imaging, last updated unknown, Reflectance Transformative Imaging (RTI)http://culturalheritageimaging.org/Technologies/RTI/ last visited 10/11/2013

Link 2: Kreylos, O., last updated 2013, Augmented Reality Sandbox,  http://idav.ucdavis.edu/~okreylos/ResDev/SARndbox/, last visited 10/11/2013

Link 3: Filemaker, last updated unknown, Jericho Mafjar Project: Filemaker Go for Ipad Modernises Archaeology, http://www.filemaker.com/solutions/customers/stories/jericho-mafjar-project.html, last visited 10/11/2013

Link 4: National Museums Scotland, last update 2013, 3dei: Hilton of Cadboll Stone: A Pictish Puzzle, http://pictishpuzzle.co.uk/, last accessed 10/11/2013

link 5: Google, last updated unknown, Google Earth, http://www.google.com/earth/download/ge/agree.html, last visited 10/11/2013

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