Tag Archives: survey

Lockdown Archaeology: a walk in the woods

By Rob Evershed, Project Officer (Geophysics)

Due to the ongoing coronavirus situation I’ve found myself confined for the majority of my time to my home. I’m fortunate in so much as I can continue working on writing up various projects, but it’s still a little claustrophobic, a feeling I imagine a lot of people are having at the moment. So my daily escapism comes in the form of walking my dog just after 4pm. I’m lucky to have some woods just up the road where I can easily go, and where I have turned my archaeological eye on.

hector the dog looking for archaeology — Hector looking for archaeology

The woods are part of a landscape of managed woodland in the area, although parts of it are slowly returning back to nature as at the moment there appears to be limited removal and replanting of trees. I’ve always been interested in the slightly unusual lumps and bumps within the wood, but never got any further than thinking it might be interesting to try and work out what might be going on.

Well finally with the lockdown I got round to doing a bit of detective work. The Environment Agency has Lidar data they provide for free on their website, and this proved perfect for getting a better look at what might be going on.

As you can see from the image, the area available for dog walking has a number of lumps and bumps, including a sub-circular swamp area extending from the southern edge. It does continue further to the south, but that’s private woodland.

However the most interesting feature I’ve noticed is the strange square feature towards the northeast corner of the area. Here’s a zoomed in Lidar image.

square feature in the lidar image — Detail of the square feature seen in the Lidar image

Exploring the area this feature has fairly clear banks surrounding a lower flattened area that sloped gently to the west. Without all the trees and vegetation it would undoubtedly stand out very clearly as a distinct feature, but with the trees and vegetation it is actually very difficult to see. Taking good photos of earthworks is notoriously difficult, and being in the woods makes it even trickier. However here are a few shots from which you might be able to make out some of the banks.

looking across the woods — The southeast corner of the woods

From it’s square shape, and distinct ninety degree angles, it definitely looks like a manmade feature. The surface geology is sand and gravel, but the woods in this area definitely pre-date the twentieth century as they are present on the 1^st Edition OS map. Nearby heritage features include a deer park, a deserted medieval settlement, and the site of a former priory. But apart from the woodland potentially being used for one or all of these places, I’m at a bit of a loss for what the square feature might be, or why it was created. Currently my imagination is suggesting it’s an Iron Age fort, but I have no evidence to back that up. What do you think?

A Day in the Life of…Alistair Branagh (Project Archaeologist, GIS and Survey)

My current role within the company is focused on GIS and survey. I am primarily based at our head office but from time to time I get released onto site to do some GPS or Total Station survey, or to provide some training in using our survey equipment to my colleagues in the field. Most of the time I can be found sitting at the computer doing GIS work.

Alistair fixing a camera — Some kind of electronics Frankenstein

What is GIS you may be thinking? GIS stands for Geographic Information System. It is a really important part of archaeology. At a basic level, it is essentially mapping. The GPS data taken on our sites to record the location of the archaeology we have found is brought to me. It is my job to firstly check the data for inconsistencies, format it appropriately and import it to the GIS. My job also involves digitising plan and section drawings and combining all of this information to create standardised figures for our reports.

It is a crucial role which allows me to be involved in many different projects and through every stage. As such I have a lot of varied tasks, ranging from georeferencing plans from clients and setting out trenches and site boundaries, to collating data at the end of a project. I’m also here to support staff in the field if they have a problem with the GPS or need an up to date plan of site. In a typical day I could be working on three or four different projects, completing any number of different tasks that are required. On occasion if a large project has recently completed, the GIS work may take up a large part of my week. It can be a time-consuming process and requires a lot of attention to detail to make sure everything is correct and accurate.

I spend some time looking after our survey equipment as well, checking that everything is working so that our field team have everything they need to do their job. From time to time I can also be found hunched over a dismantled camera like some kind of electronics Frankenstein, making sure they are cleaned and functional. On top of that, I often find myself being called on when my colleagues have problems with their computer!

It’s really difficult to try and paint a picture of a “typical” day in my job. It’s an interesting one because sometimes the days can feel very much the same but other weeks the days can vary quite a bit. It is for this very reason that I enjoy my job a lot as I never really know what the next day will bring or what new challenges will come along.

A Day in the Life of… Fabian Danielsson (Project Supervisor, Fieldwork)

I’ve been with Allen Archaeology for close to 4 years now, and have been working as a Supervisor for just over a year. My working life, like many others at Allen Archaeology, is split between periods in the office and periods out on site.

On site, my job is essentially twofold – making sure that every archaeological feature gets excavated to a high standard and on time, and making sure the recorded archive is of a good quality. To do this, a site usually starts by stripping the topsoil off the site with a mechanical excavator, and surveying in the revealed features by GPS. I then work out what needs to be excavated – we usually have a target percentage for how much of each type of feature we excavate, and also all relationships between features so that we can work out the stratigraphy of the site (the chronological order that things happened).

I then provide guidance and advice to the guys and girls digging, adjusting methods and strategies as necessary. The features are then recorded by the excavator: everything gets a drawn section, a drawn plan and a colour photograph, as well as a context sheet which creates a written description. This is the recorded archive, which I will ideally check daily to make sure it all makes sense and is correct.

Fabian in his natural habitat (complete with wellies, mud and survey kit!)

Once a site has been finished, the archive is essentially the only record that is left of the site, so when it gets to the office we need to make sure it is handled correctly. This involves downloading photographs and survey data, logging finds and scanning drawings onto the computer. Once everything is in order we can write a report, although this does not always happen immediately after a site is finished as it depends on the requirements of the project. A report has several components, including selected photographs and drawings, specialist reports of the finds recovered, and the historical background of the site. The bulk of the report consists of a written summary of what was found – this can be anything from a few paragraphs for very small sites to over 300 pages for some of the really big sites!

At the end of the day though, it’s time to go home and watch a bit of Gardener’s World…

A Day in the Life of…. Rob Evershed (Senior Project Officer, Geophysics)

I’ve now been with Allen Archaeology for 8 years and 7 months, and have managed in that time to drag myself kicking and screaming up to the exalted heights of Senior Project Officer (mostly in charge of geophysics, but also other stuff too). I can normally be found in one of two places, either chained to my desk writing up reports or helping other people with GIS issues (along with Charlotte and Mia), or out in the world on geophysics missions (or sometimes, very rarely, actually digging). I’ve found the higher up the totem pole I get, the more time I have to spend in the office. This is all well and good when it rains, or during the winter, but can occasionally be a little disheartening when the weather is nice and I’m hearing about exciting sites others are currently on.

Here I am clearly providing wise words of informative encouragement

The location for such adventures can be as far afield as Suffolk, Staffordshire, Yorkshire or even into Wales. Have magnetometer can travel.

So with a trusty minion in tow, (occasionally we require more than one team for larger jobs – I try to not let the power get to my head) I head out to the required area. I’ve worked on a large number of geophysical projects over the last 7 or 8 years, from tiny areas of less than a hectare to mammoth cable route jobs- surveying a 60m wide area for a length of 50 or 60km. Unsurprisingly during that period I’ve encountered all possible weather conditions, from blizzards to torrential rain, and thick fog to baking hot summer days. The one constant being a steady 1.5 or 1.6m/s walk across a field.

Slightly too much snow proving tricky, properly equipped with snow goggles too

Localised flooding not preventing surveying

The first job when we arrive on site is to set out the grids. Prior to the job commencing, I make sure I’ve set out grids (20m or 30m) on the computer, and we use the GPS to mark out the corner of each grid with bamboo canes- no metal allowed as it affects the readings of the magnetometer. My trusted minion will then start pegging out, we have 20cm long red pegs to go in between the bamboo canes suitably spaced to provide equal transects for me to walk along. In the meantime I’m attempting to balance the magnetometer before I can start surveying.

Balancing the magnetometer is somewhat of an art rather than a science. I need to find a magnetically quiet spot within the field to run the set-up balance program- this zeros the machine’s two probes in the earth’s magnetic field and with each other. However in order to properly locate a magnetically quiet area I need a balanced machine, and to accurately balance the machine I need a magnetically quiet area….

Once a suitable location has been found (in some cases we’ve had to take the machine away from the site to a different location, balance it, and then drive back very carefully to the site taking care not to bump the machine on the way), I run through the set-up program on the machine. This sort of looks like I’m doing a very slow square dance, involving spinning around and rotating the machine at set intervals. This process can take some time, and often I’ll run the set-up program a number of times before I’m happy that the machine is properly balanced, not complaining, and ready to start.

The rest of my time is spent walking up and down the field in either 20 or 30m transects, counting up to 21 or 31 respectively, and trying to keep my pace constant, whilst trying not to trip over and vegetation or crops that happen to get in my way, or fall down any rabbit holes. Keeping a constant pace is very important as it means that any anomalies that are revealed by the survey are displayed in the correct location on the results. We almost always use a zig-zag pattern for surveying, and if I don’t keep my pace constant it can be very clear in the results when linear features end up looking distinctly broken up and not wonderfully linear in nature. Tricky situations involve surveying up and down slopes, or through slightly thicker than optimum vegetation.

Finally, when the area has been surveyed (or the machine has filled up, it holds about 3 hectares of survey data before it needs downloading and deleting), I get to hook the magnetometer up to a laptop, download the data and get my first look at the survey. This is the best part of the day, as I’m seeing results which can reveal archaeological features that can be up to several thousand years old. Or the exact locations of modern services like gas or water pipes- they tend to show up very well.

Weary but buoyed up by happy exercise endorphins I head back to the office to show off all the exciting things I’ve found. If there’s still more to survey then I can look forward to another day walking up and down fields, if the job is complete it’s back to being chained to my desk to write the report up.

Occasionally I get to interact with local wildlife or people, mostly to explain that what I’m doing is a bit like some of the stuff they’ve seen in Time Team.

A curious local inquiring about what I’m doing

Best site hut biscuit with Harvey

What is your job role?

Project Archaeologist working in the Heritage Department. I do desk-based assessments, occasional building surveys, and general GIS work for illustration.

How long have you worked for Allen Archaeology?

About five months at the time of writing.

How would you describe your excavation technique?

Messy unfortunately. I’m better at keeping my desk neat than I am at cleaning up section edges…and my desk isn’t exactly tidy…

How long have you been working in archaeology?

On and off since 2015, starting from the end of my second year of university.

How did you get into archaeology?

I stumbled into it really, and found it a good fit. I was working in a bookshop on the high street looking for something better to do, so on a whim I looked into Hull University and chose archaeology. While I was there I found my way into research projects and volunteering on digs and in museums, then after that I ended up working in geophysics with little bits of excavation here and there on evaluation jobs. It was a really fast trajectory, especially given I didn’t do history or anything similar at GCSE or A-level. Everyone I’ve met in archaeology has been very encouraging, which helps. It’s a very friendly profession.

Archaeology in its natural environment

What is the best thing about your job?

It can push you towards being a bit of a generalist I think, at least it has done in my experience, so it’s a really good excuse to keep buying more and more books (‘I need them for work!’). Being able to keep reading up and applying that knowledge immediately is one of the most rewarding things about archaeology. I like going out on site visits too, there’s nothing like seeing archaeology in its natural environment!

Specialist skills?

Asking questions that lead to more questions rather than answers…so maybe research skills?

Best site hut biscuit?

Fruit shortcake! The little round flowery shaped ones with sugar on top, lovely with a cup of tea. Plus because they’re small you can eat quite a few at once.

Best site hut biscuit with Rob

What is your job role?

Geophysics Project Officer

How long have you worked for Allen Archaeology?

6 years and 9 months

How would describe your excavation technique?

Hulk Smash

How long have you been working in archaeology?

6 years and 9 months

How did you get into archaeology?

A long and complicated story involving being a medical student, a holiday entertainer in Cyprus and then finally a stint at Bristol University studying Archaeological Science (mostly playing hockey). That’s very much the short version.

What is the best thing about your job?

Having minions to boss around is certainly a plus, but actually it’s getting out to new sites and through the magic of fluxgate magnetometry getting to be the first person to see archaeological features that have been buried for hundreds if not thousands of years.

Specialist skills?

The ability to continue walking all day every day and cover ridiculous amounts of area whilst surveying in a remarkably short period of time.

Nothing stops Rob’s dedication to walking for geophysics

Best site hut biscuit?

Bourbon. And if you don’t think so, then you’re wrong.

Islamic Palaces 1 – The Alhambra Royal Workshops Project

Over the past 6 months I have been working with universities in the south of Spain to investigate workshops and production areas within medieval Islamic palaces. This, the first of two blogs, will focus on trips taken earlier this summer to the Alhambra in Granada.

Arabesque and tiles

For those of you unfamiliar with the site, the Alhambra is a large palace and fortress complex situated on a promontory at the foothills of the Sierra Nevada, overlooking Granada. It was constructed in the 13^th century AD during the Nasrid dynasty, a late Muslim dynasty in the south of Spain, and the palace is best known for its highly ornate arabesque reliefs, glazed tiles, pottery, glass and of course the beautiful gardens; and it was these gardens that had attracted the attention of academics from the Universities of Bournemouth, Newcastle and Granada. The question they were all asking – where exactly were the tiles, pottery and glass produced when the site was initially constructed?

The current gardens are a relatively modern addition and much reconstruction work of existing structures had been done to tidy its appearance; however, upon closer inspection some of these structures formed ‘keyhole’ shapes in plan, typical of kilns or furnaces.

Keyhole kiln

Prof Kate Welham and Dr Derek Pitman from Bournemouth University took the lead in May, undertaking a non-invasive survey of an area of garden using a whole suite of geophysical techniques (fluxgate gradiometer, electromagnetic survey, magnetic susceptibility and ground penetrating radar (GPR)), plus portable X-ray fluorescence (p-XRF). This approach was taken because of the likely nature of deposits beneath the surface – the site had been occupied by Napoleon’s forces during the Peninsular War, but upon his retreat significant parts of the fortress were destroyed including, most probably, the area of garden under survey. As little or no archaeological work had been carried out before, no one knew quite what to expect.

Surveying

Now, my first piece of archaeological fieldwork took place in 2000, and I’ve been in and out of the field ever since, but until this moment I’d never performed a geophysical survey. I’d always been that guy who can dig and, in more recent years, the GIS geek, often working with geophysical data but never collecting it. So just to prove to everyone that it did actually happen I got someone to capture the moment…

Using GPR at the Alhambra

I’m afraid I’m not able to reproduce the results in this blog, but I can say that several areas indicated the presence of high temperature activities. These results informed the implementation of an excavation strategy, and a couple of months later, two trenches were opened to investigate various magnetic enhancements recorded during the geophysical survey. These were directed by Dr Chloe Duckworth from Newcastle University and Dr Alberto Garcia Porras from University of Granada, and I was invited along to survey their findings and introduced them to the use of SfM to reconstruct a 3-dimensional image of each trench.

A trench being excavated

It was their first digging field season and the main priority was to take the topsoil off and map the uppermost deposits and any structural remains. Once this had been achieved it became increasingly apparent that the site was more complex than first thought. It had been occupied on and off for the past 800 years and many of the remains date to later activity, including the modern reconstructions which now mask the true nature of the kilns.

I hope to return in 2017 when these remains can be investigated fully and the full extent of production within the Alhambra is likely to reveal itself.

Why bother with Geophysics?

In May we told you about what geophysics is. Apart from helping to keep me fit with sometimes ridiculous amounts of walking across fields, why else do we use geophysics as part of the archaeological investigations into a site?

Commercial archaeology is often about revealing and recording archaeological remains before new development takes place. Whilst sometimes the nature of the development can be altered or adjusted to allow preservation of the buried features, in many cases we are recording the archaeology before its destruction.

In order to reveal and record archaeological remains we first have to find them. No matter how much we might wish it, not every field has a buried Roman villa, or a medieval settlement just waiting for a keen archaeologist to come and dig it up. In many cases the most exciting hidden treasure within a field is a former field boundary and a few modern field drains.

This is where a geophysical survey can help provide the information necessary to evaluating the archaeological potential of an area and allowing the development of a suitable plan to gain as much information as possible before building work commences. The survey can allow specific pinpointing of trial trenches over the most interesting features. This is much like keyhole surgery, hopefully producing maximum results for minimum effort and cost.

So how effective can this keyhole approach to archaeological remains be? If we take as an example a site in northeast Lincolnshire near Grimsby, we can see how useful this approach can be. The entire site in question was approximately 19 hectares in size, of which 11 hectares was suitable for the geophysical survey. The remaining area was either too overgrown or flooded making it impossible to survey. Fortunately the 11 hectare area covered the entire area proposed for construction.

An assessment of the archaeological and historical background of the area had revealed possible prehistoric to Roman cropmarks to the northwest and west of the site, with medieval activity involving earthworks and find scatters located immediately to the southeast of the site. The geophysical survey revealed a lot lot more.

Results of the geophysical survey

Suddenly the archaeological potential of the site has increased markedly. Not only can we clearly see the modern system of land drains cutting across the site, but we can also see potential settlement and agricultural enclosures, as well as ridge and furrow cultivation practices. A large dipolar spike, the white circle with a black centre to the right of the centre of the site was also tentatively identified as a potential kiln.

So what happens next? Before geophysics was available, a number of trial trenches would likely have been placed within the field to attempt to reveal any archaeological remains. As you can see from the results however, there are large areas of the field where the geophysics has not revealed any archaeological features. Random trial trenches would be just as likely to miss the interesting areas as to hit them, and an incomplete picture of the archaeology would be more than likely obtained.

Now that a geophysical survey has been done, the trial trenches can be located to test the results. This is useful for two reasons, the first is that we can target archaeological features to gain a better understanding of what’s going on, and hopefully retrieve sufficient finds to allow us to comfortably and confidently date the features. The second reason is more for the benefit of the geophysicist. The results from the trial trenching can be used to validate the geophysical results. I was fortunate to be involved with the trial trenching and it was very satisfying to see how well the archaeological features within the trenches matched up with the geophysical results.

Trial trenches overlaying the geophysics

The yellow features within the trenches relate to archaeological features, whilst the black features represent furrows. Finds recovered from the features allowed us to date them from late Iron Age to the Roman period, with the furrows indicative of medieval farming practice. The large dipolar spike was revealed as hearth or kiln, although its precise date or function unfortunately remains unknown.

The results from the trial trenching correlated very well with the geophysical survey, and this allowed us to gain a much greater understanding into the archaeological potential within the site.

So why bother with geophysics? Hopefully I’ve managed to give you a window into just how useful it can be. I certainly think it’s worth all the walking I do, and although I don’t find something exciting every time I go out, I do feel I’m helping us to understand more about our buried past.

Diving into the world of archaeological geophysics

I initially wrote to Allen Archaeology to see if I could gain experience of geophysical surveys in a commercial environment: the equipment used, data analysis and how this relates to the archaeology of the site. I am a geophysics student at University of Southampton, I don’t specifically study archaeology unless chosen as a specialism, but Allen Archaeology kindly offered me a month long volunteer placement. When I started I didn’t know much about archaeology at all; how the two fields of study were related was something I was very keen to learn!

Doing a magnetometry survey

I was immediately put onto a project with the Geophysics Project Officer, Rob Evershed. We were to use magnetometry to survey the subsurface of the Lincolnshire countryside and detect any potential archaeological sites. The survey techniques themselves were very similar to the geophysics I had completed on field trips at university: marking out the survey grids before walking a magnetometer over the ground. The only difference was the equipment had a much higher resolution and is far more expensive to run.

The data analysis on the other hand was completely new. The results were produced in a program called Terrasurveyor and were completely different from magnetometer results I had previously seen. Instead of looking for geological structures as I have done at university, we wanted to find archaeological sites. Rob was great at pointing out distinguishing features in our data and explaining their significance; such as land drains, old roads and other details which would have been inconsequential to someone untrained in archaeological geophysics. Rob taught me how background research into the area and georeferencing of old maps onto modern ones could reconcile anomalous geophysical results with archaeological evidence.

Rob showing me how to process the data

When I haven’t been out in the field I have been able to help out around the office; completing small tasks on QGIS, washing artefacts and trying to piece together a Roman tablet. I’ve had the chance to explore the archives and learnt a lot about the differences in pottery from various periods; I also had the shocking experience (for a non-archaeologist) of coming face to face with a skull!

During my time with Allen Archaeology, I have become more confident in the use of magnetometers and GPS with geophysical surveys and developed my knowledge of computer programs such as QGIS and Terrasurveyor. I have learnt how to interpret geophysical surveys and use them to find archaeological remains; and most importantly through Rob’s instruction, I have learnt how to compare the archaeological evidence (e.g. pottery) in a field with the geophysical data collected and been able to draw conclusions about the history of the area based on all the evidence. I have enjoyed my experience with AAL a lot and when I return to university in September, I am definitely going pick a couple of archaeology modules to compliment my geophysics studies.