Category Archives: Geophysics

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…. 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

Romans, Remembrance and Ritual

By Isobel Curwen, Heritage Research Supervisor (and osteologist on the side)

Warning: images of human remains feature in this post

Last month, we were invited by the International Bomber Command Centre (IBCC) to take part in their ‘Hands on History’ event as part of National Tourism Week. This event saw many attractions within Lincoln (and the UK) open their doors for free!

So on a sunny Saturday morning at the beginning of April I find myself arriving at the IBCC carrying a box containing the remains of a decapitated Roman individual (SK 1026). Luckily I didn’t get too many strange looks…

Wondering why? During 2014 – 2016 Allen Archaeology were involved in the excavation work prior to the IBCC and the memorial Spire being built. Early geophysical investigations had identified several anomalies within the area which were then investigated by a series of excavations in the location of the IBCC building and spire, the car park and the access road off Canwick Hill (Evershed, 2014).

During the course of the archaeological works on the site, the excavations revealed the remains of three Roman pottery kilns, two corn dryers, and 15 Roman burials, dated to the 2^nd to 3^rd centuries. Several possible quarry pits and linear ditches were also found. The final report is forthcoming, and will be published in due course, but preliminary analysis of the results of the archaeological investigations suggest that the site was formerly a self-sufficient Roman settlement complete with corn dryers and ditches marking the boundaries of the settlement. It is thought that the quarry pits were used to mine for limestone, a readily accessible resource which was used to build many parts of Roman Lincoln. The geographical location of the site, on high ground within close proximity to the city was also an important factor.

Interestingly, the graves were found on a variety of alignments and one individual was found with the head and some of the cervical vertebrae between the legs (suggesting they were decapitated), and another individual was found buried prone (face down). Burials of this type are occasionally found in Roman cemeteries and are referred to as ‘deviant’ burials.

So, bearing all this in mind, the event at the IBCC was Roman themed and I took along the individual that had been decapitated as well as plans and photographs of the site during the excavation. I laid out the individual in the way they were found in the grave and got many questions as to why I had put the head by the feet! I secretly enjoyed the look on people’s faces when I told them why…

It was a busy day and we had around 90 people visit. Personally, it was a great experience to be able to explain to people that the IBCC, now a focus for Bomber Command during WWII, was once a Roman settlement. Even more exciting was to be able to be showing an individual that was found beneath the building we were actually standing in!

Many thanks to Cova, Yvonne, Harvey and Chris for their help in the preparation of this exhibition and on the day itself too! Thanks also go to Emily from the IBCC for organising the event and for asking us to be involved.

Evershed, R., 2014, Archaeological Evaluation Report – Geophysical survey by magnetrometry for the proposed Bomber Command Memorial and Interpretation Centre, Canwick Hill, Canwick, Lincolnshire, Allen Archaeology Ltd