Data Integration In Geophysical Surveys

Data Integration In Geophysical Surveys

“The best archaeologist, in spite of everything is still a vandal that destroys his document while reading it”
André Leroi-Gourhan

Introduction
This quote from the structuralist archaeologist, André Leroi-Gourhan shows the main problem of archaeology, which most people do not realize. One of the first things I learnt when I started my degree wasthat when an archaeologist excavates a settlement, he destroys it. In a few weeks or months he destroys something that has been buried and preserved during centuries, or even millennia.
Not only he physically destroys most of the settlement itself, but more important he surely is losing information in the process of excavation, and archaeologist are not looking for “stones” or “swords” or“treasures” they are looking for people, their behaviour and their ways of thinking. As we now have improved our excavating methods from those whom people who preceded us had, people of the future may have better excavation techniques and we are now loosing information that could be recovered in the future. This is why surveying is so important. As Mark Bowden states with his metaphor of the clinic and thesurgery (1999, p. 23), excavation is not always necessary for gathering the information we need, most of the time is one part of a bigger process. Nowadays with the improvement of the techniques and equipment in the geophysical subject we can survey areas gathering big amounts of information that helps us to decide better where to start excavating (or even if it’s worthy to excavate!).
In thisessay we will focus on the aspects of method integration and how the use of complimentary techniques may provide a greater comprehension of the nature of buried archaeological remains.

What Is Integration?
First of all we need to define what integration is, in order to better understand the topic we are talking about. There are various methods of geophysical surveying; each one of them isbased on different aspects of geophysics, each one of them has its advantages and disadvantages and each one of them will give different results of the same sub-surface and will show different aspects of what is underground. What integration is all about is to know how we can combine different techniques in order to get the best result possible. Depending on what we are looking for, what we think maybe under the ground.
Clark (1996: 29) says that the fullest information we can find about a site is by using all of the methods in geophysical surveying. If we know or we have an idea of what is below our feet, we should choose the best method to the site we are surveying.

The Methods And The Results
For better understating how we can integrate the different techniques, now we will see in alittle bit of more detail what the most common methods (although there are more) are and what kind of response they give (Bowden, 1999: 119-123):
* Electrical resistivity: this method is based in the measurement of the resistance to the passage of a current through the soil and what is in it, between a certain numbers of probes. This method is useful detecting stone structures.
*Magnetometry: this surveying is based on the existence of magnetic anomalies in the weakly magnetised iron oxides in the soil caused by human activity, such as heating over the 800 degrees C. So this is useful finding pits, ovens, kilns, bricks, tiles, hearths and ditches. But its success depends much on the subsoil type, as certain ones as igneous subsoil may interfere in the readings because of theirhigh magnetic background. But they have the advantage of being read through very portable devices.
* Magnetic susceptibility: very similar to the previous one, this method measures the ability of a material to be magnetised by an external field. Results are displayed in colour and they indicate where the most magnetic susceptibility is.
* Ground Penetrating Radar: this technique is...