Revealing the Past
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Axel G. Posluschny: Revealing the Past: The Use of Modern Remote Sensing Techniques in Archaeology Presentation at the ESOF conference, 12/7/2012
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Revealing the Past
- 1. www.archaeolandscapes.eu ArchaeoLandscapes Europe Revealing the Past: The Use of Modern Remote Sensing Techniques in Archaeology
- 2. www.archaeolandscapes.eu ArchaeoLandscapes Europe Content • Chair - Anthony Corns • Axel Posluschny - Introduction to Remote Sensing: Archaeology & Technology • Jörg Bofinger - Airborne Laser Scanning / LiDAR • Rob Shaw - Using Remote Sensing for World Heritage Sites • Christoph Steffen - UAVs & Drones • Discussion
- 6. www.archaeolandscapes.eu ArchaeoLandscapes Europe Swords • Magnetometric Survey A Soviet An-12 Cub aircraft, modified for anti-submarine warfare with nose radome and modified tailcone for magnetic anomaly detection (MAD) equipment
- 22. www.archaeolandscapes.eu ArchaeoLandscapes Europe Swords • LiDAR /Airborne Laser Scanning
- 23. www.archaeolandscapes.eu ArchaeoLandscapes Europe Ploughshares • LiDAR /Airborne Laser Scanning
- 24. www.archaeolandscapes.eu ArchaeoLandscapes Europe Ploughshares • LiDAR /Airborne Laser Scanning
- 25. www.archaeolandscapes.eu ArchaeoLandscapes Europe Ploughshares • LiDAR /Airborne Laser Scanning
- 26. www.archaeolandscapes.eu ArchaeoLandscapes Europe Ploughshares • LiDAR /Airborne Laser Scanning
- 27. www.archaeolandscapes.eu ArchaeoLandscapes Europe ArchaeoLandscapes Europe • EU project, funded from the Culture Programme 2007–2013 • at present 57 project partners from >29 European countries – start: 15 September 2010 – end: 14 September 2015 – EU-Funding: 2,5 Mio € – Total Budget: 5 Mio € – landscape archaeology related work, including LiDAR, geophysics and all other kinds of remote sensing – education, networking, dissemination, raising public awareness, ...
- 28. ArchaeoLandscapes Europe feel free to visit us at http://www.archaeolandscapes.eu
Notas do Editor
- When most people hear about archaeology, they think of adventures, exotic countries, nice landscapes, treasures and bones. Indiana Jones and Lara Craft are great movies, making use of a wonderful clichès - but not more than that. To cite Indiana Jones „Archaeology is the search for facts, not truth “ - and that is done by precise methods, by excavations and scientific measurements. While treasure hunting was only part of archaeology in former times or part of illegal looting nowadays, excavations and the resulting finds and structures are still an important source of archaeological knowledge. But the tool box of archaeologists has been expanded since a couple of years now.
- Things have changed since the first pictures of archaeological features have been taken from an airplane in the 1910s or 1920s. New techniques have been developed and adopted for archaeology, so it ‘ s not Indiana Jones representing modern archaeology but people working with sophisticated archaeological eqipment - which also sometimes may look a bit mysterious.
- And it is not witchcraft we are doing. Technical methods applied to archaeology offer a new and in many cases much broader insight into single archaeological sites or even landscapes. But of course, I confess, some of the results as you can see here, do also look rather mysterious, even more than the fancy instruments we sometimes are using. It is our aim to demystify some of these techniques and to share with you some of the results that we could gain from modern surveying technology. Archaeology can be exciting, even when the pictures that you can see here appear a bit boring. But they reveal some interesting information for the knowing as we will show you today.
- Archaeologists are very good in adopting methods and technologies from other disciplines. Many of these methods have been borrowed even from military context. I guess it ‘ s correct to use the picture of swords into ploughshares for that kind of use and the use of magnetometric survey is a good example for that. The differences in the earth ‘ magnetic field that is caused by objects - the so-called magnetic anomaly - is used to detect for examples submarines from the air.
- But also archaeological objects and features that are buried in the ground can create magnetic anomalies which can be measured with a geomagnetic device which can be drawn by a car or carried by man.
- Everything that humans do with the soil leaves its marks in the soil. Stones of an ancient wall are still in the ground, changing its texture. Ditches get refilled by ploughing after a while - again filled with soil of a different texture. In archaeology - like in submarine detection - features that differ from their magnetic values from their surrounding can be detected. A submarine has a differrent magentic value than the surrounding sea, and a stone, especially when burned, or the different soil in a former ditch have different magnetic values than their surrounding soils. These differences can be measured and can be represented in a plan that shows the magnetic values of a measured area.
- You can see here an example for such a resulting plan of certain features that are hidden in the soil. This plan for example shows the result of a large scale geomagnetic survey in Slowakia with traces of a ditch fortified Bronze Age settlement, a Neolithic eathwork and houses and a Roman military camp. Archaeologists use these methods to detect unknown sunken features, but also to investigate an area before an excavation takes place to know where which kind of features can be expected when digging op the ground. You can compare it with a doctor who is making an x-ray scan before doing a keyhole surgery - not cutting the whole body open to find out what is wrong and where.
- Looking from above and having a larger overview was (and still is) one of the first and main reasons why planes have been used in warfare. It was not so much the attacking possibilities of aircrafts that were important for first world war pilots but the ability to see the enemie ‘ s ongoing activities on a larger scale and in a wider context. This overview, this aspect of contextualisation is of course also important for archaeology.
- So not only soldiers wanted to know what can be seen from above. Archaeologists soon discovered that known archaeological sites can be documented and even newly detected from the air. As already mentioned, buried structures leave marks in the soil which can be traced for a very long time, even for several thousands of years. Whereas a ditch usually provides a much more humid soil, the soil above a buried wall can be much dryer. Both result in different appearance of the soil itself or in a differing growth of plants.
- These features can be seen from above, and moreover they also can be seen in a context with other features, forming a picture which the archaeologists can interpret. The example shows various sunken features like pits and ditches that form a prehistoric settlement in the Czech Republic.
- You can see a number of storage and garbage pits that preserved more humid soil conditions, resulting in a better growth of teh crops.
- A ditch has been surrounding a prehistoric house
- And when you look carefully, you can even detect the postholes from houses that were build in a timber-frame construction, very regulary distributed in a 3 by 4 pattern on the left hand side.
- And yet another feature is a larger ditch structure (KLICK) which might not have belonged to the same phase of the settlement as it seems to be overlapping (or is overlapped by) some of the pits that we can see.
- Satellites use the same principle as observers from airplanes and they have been in use for such purposes especially during the cold war in the late 20th century.
- But of course archaeologists found out, that on these images not only tanks and missile bases could be seen, but also archaeological sites or landscapes and their use. The satellite image on the left hand side shows the development of an archaeological site in Sudan - images from different periods show the landscape and its change. While it was rather costly to buy these pictures in the past, tools like GoogelEarth allow the archaeologists as well as any interested laymen to depict archaeological features from an armchair - like the gigantic Bronze Age earthwork in Romania on the right hand side.
- The site has a number of large ditch systems. Some of them seem to be more or less straight lines, but most are circular ditches with gaps that might indicate entrances.
- From fieldwalking and smal excavation trenches we now know that this site dates to the Bronze Age, which makes it 3500 years old, or maybe even older.
- To give you an idea of the size of this site: the length of the red line you can see here is more than 2800 meters long!
- The military has always tried to gain information about the topography of battlefields, lines of communication and the landscape in general. Airplanes and satellites have helped to get this information, either by photographs or by precise measurements
- With the further developement of radar measurements (again a technique that was invented for military purposes) it became possible to use satellites to measure a digital elevation model - a height model of the earth ‘ s surface - with a ground resolution of 25 m or even less. Measurements from an airplane or a helicopter can provide an even more detailled picture of the topography with a resolution of 20 cm or below. Small differences in height which can be caused by very shallow ditches and ramparts of a Celtic hillfort - like the one from Glauburg in Germany you can see here here on the right - are not visible from the ground but they become easily recognisable on a shaded relief image from a LiDAR scan
- LiDAR - short for „Light Detection and Ranging “ is measured from the air with radar like laser scans. With the help of a GPS device the coordinates of each measured point on the ground can be calculated with very high precision. Jörg Bofinger will tell you a bit more about it later. One of the big advantages is the possibility to not only measure the surface of the ground in open areas but also in terrain that is covered by bushes or trees. Special filtering algorithms allow to digitally remove these features so that prehistoric grave mounds can be discovered by their height differences even in the woods as you can see on the grayscale picture.
- The picture here shows the LiDAR scan of a Celtic hillfort in the Czech Republic, densly covered with trees and bushes which you can see here as the darker areas.
- After a bit of advanced filtering the vegetation has been removed and the image impressively shows the ditch and rampart system of the hillfort as well as a number of other features.
- Those are just a view of the surveying techniques that archaeologists nowadays use. But funny enough, even when they all have an enormous potential to discover, document and monitor archaeological sites and landscapes, their use is not equally distributed all over Europe! Hence the EU supports the „ArchaeoLandscapes Europe “ project which aims to overcome these differences and which promotes the use and the benefits of these techniques on a European level.
- My colleagues will now show a number of examples for some of the methods that I have shown you. Thank you very much for your attention!