Stonehenge with sun rising

Time team technology

Many will have had their view of archaeology provided by episodes of 'Time Team', but what equipment does the modern archaeologist have at hand?

The modern archaeologist has a whole array of equipment at hand nowadays to help locate and catalogue their finds. "Most people are very familiar with the term geophys or geophysics from Time Team where they are normally working on land and what you generally see on those programmes is people using magnetic gradiometer systems to detect small variations in the Earth's magnetic field to identify features such as ditches and walls," says Dr Paul Baggaley, geophysics manager at Wessex Archaeology. "The reason those features show up is because the soils filling the ditches have different magnetic properties from the bedrock which the ditch is cut into."

"The changes are only very small in the order of a few nano-tesla; the whole Earth magnetic field is about 48,000 nano-tesla round the UK and we are measuring down to about 0.1 of a nano-tesla with the equipment," he explains. "So it is just a way of using very quick tools to map out over an area what we think a spatial distribution of these features are, which we can then use in GIS to plan or plot against other desk based information to help the archaeologist work out where they need to target trial trenches and other parts of the excavation."

The depth of investigation varies on the equipment and on the geological properties of the site being investigated. "The fluxgate gradiometer systems that are very common on Time Team generally only see down about half a metre or so," says Baggaley. "You can get other magnetic systems on land called total field systems, which can measure down to about a metre at most, so if you have a lot of aluvian over a site - say near a river system - it could be very hard to detect any archaeological features."

"For data capture we make use of fairly industry standard equipment which includes total stations which are now fully robotic and can be operated by one man with all the control being on the pole," says Paul Cripps, geomatics manager at Wessex Archaeology. "We have a fleet of survey grade GPS units which we use for recording all our archaeological excavation sites and we also use tools like mobile recording units, so we have GIS running on these with structured recording systems which allow us to capture data in a structured fashion out in the field which can then come directly through into our office database systems."

"When we work offshore, the marine magnetometers we have are only as sensitive as the ones we have on land, but generally offshore we are looking to identify shipwrecks, which have magnetic anomalies of many thousands of nano-tesla, so they are generally easier to find," says Baggaley."We can't get the magnetometer as close to the seafloor as we can get the magnetometer close to the surface on land but we are looking for bigger features so using this equipment is still a very successful way to map out large areas very quickly," he explains.

Magnetometers detect metals very easily and are very easy to identify. "However, on terrestrial sites a piece of metal on its own is generally not very interesting," he says. "We are looking for smaller features or features which are going to be of more interest such as ditches, buildings, roads, pits and those kinds of sites. We generally can't identify graves and burials and bones; they are just too small to be sampled properly or are not magnetic enough."

There are lots of other types of equipment that geophysicians use. "On land we have ground penetrating radar which is very good at giving us a vertical slice down through the earth and different frequencies and antennas will give different depths of investigation and they are very good systems to use over features like walls and buildings," says Baggaley. "If you have a villa you can see the extent of the wall going down to a metre or metre and a half below the surface."

However, ground penetrating radar can't be used offshore, "but we have acoustic based systems, such as boomers, pingers and chirps, which can give us a vertical slice down through the seafloor and we use these to pick out paleogeographic features, such as large buried paleochannels (in filled river channels), which are very important for us to find because they give us an indications of what the landscape looked like before it became submerged," explains Baggaley.

We tend to think of the land as just stopping and the seashore being fixed but there were continuous landscapes that stretched all the way from England to France and all the way across the North Sea from England to Denmark, so there are huge areas out there that we need to explore and understand.

"The area that is now covered by the sea is now land and has been covered by the water and re-exposed many times over the last million years, but it last became flooded about 10 - 13,000 years ago and so if we look further back than that we start to see some examples of really ancient sites of human occupation and it is offshore where we are going to find those really old sites that we are missing on land at the moment in some cases," says Baggaley.

"A project called Sea History uses various visualisation techniques to provide a picture of how we believed a landscape was that is now submerged under about 30m of sea off the coast of West Sussex," says Tom Goskar, archaeological computing specialist at Wessex Archaeology. "We've used a number of technological approaches to make a short animation based on the seismic evidence from geophysical surveys taken a number of years ago," he explains.

The animation was used to test a number of hypotheses and was created with input from geophysics and environmental specialists and designers. "We are talking about 10,000 years ago about 8,000 BC during the solithic period and the river Arun continued out of West Sussex into the area just east of the Isle of Wight, which since the melting of the ice is now submerged," says Goskar. "We were able to take the seismic data and use it to create a three dimensional surface which represented the channel of the river Arun in our study area. Our environmental team then took a series of cores samples across our study area and from the sediments in those core samples the team could then work out what was growing where," he explains.

"We looked at this landscape and defined a series of zones and we worked out the environmental characteristics for each zone and transferred this into the software to create an image," says Goskar. "We were able to source 3D models of many of the plants and trees growing there at the time but for the others we used some software called Xfrog to take photographs of leaves and bark to actually create our own 3D plants. Once we had all the 3D parts we turned it into our landscape."

Word War II bomber

"In terms of age, the sites we date range from about a million years ago right through until about ten thousand years ago at the end of the last ice age," says Baggaley. "But we also look for sites right up to the modern day, so we have even found offshore sites with Second World War bombers on them."

He explains: "We know areas where there are lots of shipwrecks, such as the Goodwin Sands off the coast of Kent. It is an area where the sandbanks are large and have moved a lot. They move ever year so are difficult to chart and with a seafloor like that there is the potential for ships to be lost in a storm on a sandbank and very quickly covered and then uncovered tens or hundreds of years later. The German bomber for example may have landed on a sandbank and at sometime it was flipped over and landed on the seafloor and may have been covered by sand but has recently been uncovered and looks to be in very pristine condition."

Data management

"Moving through into the recording and analysis side of things - all the data we capture out in the field comes back and goes through various pieces of software to end up in our integrated database GIS environment," says Cripps. "We can then pull all this data together using structured frameworks and analyse and manage that data efficiently so that we can come to an understanding of the past. That is what it is all about as far as archaeologists are concerned. We are trying to understand what happened in the past and these are all the tools that get us to that point."

Cripps confides: "Increasingly it is the way in which we structure our digital data that is important because we are not just working in isolation, so the data that we produce will go in to form part of archives which other people will want to use and increasingly, that is happening on an international scale."

"So there are pushes in the academic community and within national government bodies like English Heritage for example, to have overarching frameworks that can actually pull the data that we produce together with other data from other sources to allow us to do amazingly interesting things on an international scale," says Cripps.

The vast majority of Wessex Archaeology's data has some spatial component, so working with that data in a map type environment is by far the most logical way of handling it. "As well as allowing us to pool all our data together and produce maps, analyse, interpret and ask questions of our data, our GIS and databases also facilitate the ultimate in dissemination and archiving stages of the process," says Cripps. "So by having structured data that is born digital and flows through our various processes we then end up with data that suitable for all kinds of online presentation and electronic dissemination in various forms."

Wessex Archaeology is looking at using things like online GIS to allow external interaction with its data for project purposes but also to disseminate that data, so it can use platforms such as Google Maps, which is a freely available platform, to get the data out to the public.

"Another strength of that is Google Maps will run on mobile devices such as smart phones, so as part of our outreach activities we do things like build virtual tools for people, so we can actually put some of our archaeological information out there in a way that anybody with a locationally aware device, such as a smart phone can wonder around the landscape and find out more about where they are."

He concludes: "Obviously that isn't suitable for all of our datasets, such as the big laser scan datasets but for many things, such as archaeological monuments out there in the landscape it is a brilliant way of getting the public to engage with archaeological information using technology."

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