Geophysical imaging

Novel electrical resistivity tomography @ The University of Bradford

Today, like almost every day between May and September this year I’ve been working on my MSc research Project. Instead of just explaining what I’ve been doing today i thought it would be more interesting to describe what is going into my individual research project.

I’m experimented with a new novel way of collecting electrical resistivity tomography data  with a zzGeo FlashRes64 which as you might expect involves a significant amount of lab and field data collection.

To allow inversion of these novel techniques far too much of my time has been devoted to developing software to allow analysis of the data, and investigation of different visualisation techniques. Though  it does make a nice change from the driving rain outside.

FlashRes to Geotomo program

Before going out in the snow and rain its important to know that the data collected will be as good as possible. This means i spend a lot of time visualising different data collection techniques as point clouds as below. I promise they end up being quite relaxing.

Eventually after determining the best collection strategy, standing out in the rain and the cold for hours, extracting, converting and comparing data you do end up with a decent representation of whats beneath the surface.

 

P.S You should be able to zoom and play with the images above. If you can’t i’d suggest a modern HTML5 compatible browser

Discovering Dumfries and Galloway’s Past

Well, hello from a soggy south-west Scotland. I’m Giles, Development Officer for Discovering Dumfries and Galloway’s Past and I wanted to tell you on Day of Archaeology 2012 about the project and what we are going to be doing over the next week or so…

DDGP is an exciting new community archaeology project based in south-west, providing training in using geophysical survey to help volunteers record, understand and interpret the region’s fascinating archaeology. There’s going to be plenty of opportunity for local people right across the region to get involved in the surveys – it’s a great way to find out more about buried archaeology without having to excavate.

What is geophysics, and what can we find out using it?

Not all archaeology is about excavation – you may have come across ‘geofizz’ on TV’s Time Team where it’s often used to plan where to put the trenches in. Geophysics is a way of mapping buried archaeological deposits – be they ditches, pits or building material – without ever breaking the ground surface.

There are two main techniques for geophysical survey:

Glasgow University archaeologists undertaking resistivity survey

Resistivity: By passing a small electrical current into the ground, and measuring the amount of resistance that results, it is possible to locate buried remains of archaeological interest.

Resistance is related to the amount of moisture in the soil. Around buried walls, for example, the surrounding soil will often be dryer. The current cannot pass so easily through this dry soil, so stonework can often show up as areas of higher resistance. This technique is therefore ideal for locating building walls and foundations.

Glasgow University archaeologists undertaking magnetic survey

Magnetometry:  This technique detects extremely small variations in the earth’s magnetic field, caused when the ground has been disturbed by previous activity. Burning, for instance, will often leave a significant magnetic trace.

Magnetometry is excellent for locating ditches, pits, middens, hearths and kilns – and is great at covering large areas quite quickly.

The great thing about geophysical survey is that the results can be rapidly downloaded on site to a laptop, and even with minimum processing it is possible to define ‘anomalies’ which can represent buried archaeology. For volunteers on the project surveys this is great – they can see the fruits of their labours in the field. We are aiming to get these very quickly into reports which will be uploaded onto our website, to share them with as wide an audience as possible.

Our next survey
It’s all a bit hectic in the office today as we put the finishing touches to our programme for next week’s survey. We’ll be undertaken both magnetic and resistivity survey at the nationally important site of the Roman fort at Birrens. This continues work that the University of Glasgow have been concentrating on – looking in and around Roman military sites in Eastern Dumfriesshire.

Magnetic survey results around Bankhead Roman fort, Dalswinton

This has looked at fabulous sites around Lockerbie, such as the Roman fort at Dalswinton. As you can see this has added loads of detail (as you can see on the right) to both the inside of the fort of Bankhead and the surrounding area – which aerial photographs have shown to be really interesting.

At Birrens Roman fort, near Middlebie, we’ll be focusing on similar things. A group of 6 volunteers will be joining us for 3 days next week to carry out some resistivity survey on the interior – hopefully we’ll get detail of the street pattern, as well as an idea of how the buildings – both the barrack blocks and administrative headquarters of the fort – were laid out.

You can find out more about Birrens fort – known to the Romans as blatobulgium (literally the ‘flour sack’) here.

We’re having an Open Day on Saturday July 7th – it’ll be a great chance to show the public the results as well as an opportunity to show just how geophysics ‘works’ – including the amount of walking in straight lines that’s involved! The response has been fantastic locally – so here’s hoping for some sunshine!

I hope this has wet your apetite both for ‘geophysics’ and the project – please see our website to keep up to date with the latest – discoveringdgpast.wordpress.com.

The project is jointly funded by the Scottish Government and The European Community, Dumfries and Galloway Leader 2007-2013; The Crichton Foundation and The University of Glasgow.

Archaeo-Geophysics in the Netherlands

Hello! For me, the day of archaeology will be a day of interpreting geophysical data which I collected earlier. I’ll start off with a coffee and fire up my computer. I will have to spend the day behind my computer rummaging around with my GPR- and magnetometry-data. Looking through my eyelashes, trying different colourmaps, data-filters, studying other available information just to see if geophysics will reveal certain lines, shapes and anomalies in general.

Conducting geophysical surveys for a commercial firm in Holland is what I do. Officially educated as an geologist/geochemist, I spend a lot of years in the environmental engineering field (soil surveys, soil remediation), but the combination of geophysics & archaeology was always appealing to me. At our firm Saricon, we also look for UXO’s, but my main field of interest is the world of archaeology!

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Day of data processing – geophysical survey results from Isola Sacra

A day of processing of data, starting with the latest results from the geophysical survey at Isola Sacra, near Fiumicino, Italy.

 

 

This image shows a member of the survey team last year surveying using a fluxgate gradiometer over the central part of the landscape, an area of floodplain between the course of the river Tiber and the small Fossa Traiana, which demarcates the Isola Sacra between Portus and Ostia Antica. So far some 120 hectares of data have been collected, and the latest stage of processing is under way. More to follow later.