Datchworth Church

Something a little different this time. The CAGG team were asked a favour by the Parochial Church Council at Datchworth.  Basically, they are running out of space in the graveyard.  A local farmer has offered them some land to extend the cemetery, but because of the possibility of archaeological remains in the area they need to have an assessment done before they can extend the churchyard.  Some ten years or so ago, the Welwyn Archaeological Society did some limited excavations in the area prior to the building of their church hall, and so we were approached to see if we could do a geophysical survey.  The area which will be affected is quite small, so we did the mag survey of the entire field over a day and a half, during which time we managed a resistance survey at 0.5m spacing of the key area.

The resistance survey at Datchworth underway, 19/4/2014.

The resistance survey at Datchworth underway, 19/4/2014.

We undertook the survey over two days, the 13th and 19th April 2014.  The mag survey was finished by lunchtime of the second day and would have been even quicker if it wasn’t for the awkward shape of the field — resulting in every grid (bar one) being a partial.

Results of the magnetometry survey.

Results of the magnetometry survey.

The mag survey shows… not a great deal.  The important area to the north of the current churchyard shows nothing much at all.  To the east of the church there are some potential features, but the most likely area is the northern part of the survey.  This spot also has lots of lumps and bumps and the farmer thinks there may have been a building there.  The clarity of the survey is badly impacted by the large quantities of farm machinery parked there and a farm shed.

Results of the resistance survey.

Results of the resistance survey.

The resistance survey was much slower.  When taking readings every 0.5m, it takes a day to cover the area the mag completes in about 40 minutes!  The high resistance feature (shown in black) that runs along the western edge of the survey, is a bank running parallel to the ditch that runs along the road.  The other features are not visible on the surface.  High resistance features are usually things like roads, paths, walls and sold floors.  In this case, we appear to have a linear feature running N-S to the west of our survey area as well as a second one near the “moat” at the top.  I need to ask around a bit more before committing myself to a particular interpretation, but they are certainly too wide for a wall.

 

 

Little Hadham

Today we ventured out to the east of the county to survey near Little Hadham. We had done a little survey at the site last autumn but returned to examine a more fruitful looking field today.  Many thanks to all who turned out, we had quite a large team.  As we wanted to finish the area we knew contained features we worked on until 6pm.  I think the results were worth the effort.

Results of the survey on 6th April 2014.

Results of the survey on 6th April 2014.

The surface finds included late Iron Age and Roman pottery and it looks like we have a small enclosed farmstead with an associated field system.  Clearly the features go further to the south and east, and metal detector finds show that it continues to the west on the other side of the road.  Previous survey suggests there is not much more, if anything, to the north.

The ridges from the cultivation show in the plot as the lines to running east-west, and there is a little stagger error, but nothing too bad.  We can’t always survey on nice smooth parkland!

Another success for the CAGG team!

News Update

End of term madness as well as conferences in Basel and Reading have stopped me from working on the project for a few weeks. Yesterday I spoke to the Roman Archaeology Conference in Reading and there is great interest in our results.

A couple of upcoming events.  On Thursday evening (3rd April 2014) I will be delivering a lecture about the project as part of Verulamium Museum‘s Thursday evening lecture series.  It starts at 7.30pm at the Museum, all welcome.  Then on Saturday 5th April I will be giving the Gordon Moodey Lecture after the AGM of the East Herts Archaeological Society which is to be held in Great Amwell Parish Hall, 2.30pm.

We plan to start surveying again very soon and we will be emailing the trimmed down mailing list about that soon.  Meanwhile, a few photographs to remind you all of the joys of working in Verulamium Park in the wettest winter on record.

Ralph Potter (WEAG) teaching UCL students how to use the GPR.

Ralph Potter (WEAG) teaching UCL students how to use the GPR. Note the mud on the wheels!

Jim West (CVAS) negotiating the trees and undergrowth near the southern edge of the site.

Jim West (CVAS) negotiating the trees and undergrowth near the southern edge of the site.

Rainbow over the Park.

Rainbow over the Park.

Ralph’s great data

Last Monday and Tuesday we were out in the Park, partly continuing our survey but mainly to teach masters level students from UCL.  Many thanks to Jim West, Pauline Hey, Mike Smith, Peter Lilley and Ralph Potter for acting as unpaid teaching assistants!

Although we did some magnetometry (with both the Foerster and the Bartington) and some resistance, the star of the show is Ralph’s Ground Penetrating Radar (GPR) data.  Ralph provided me with a movie showing his results and the raw data.  I’ve long wanted to learn how to slice GPR data so with Larry Conyers’ program, and Larry’s patient help, I sliced the data myself.  Many thanks to Larry and Ralph for their help and the data.  The first image below shows the location of the GPR survey: a 50m by 40m grid partly over the 1955 ditch but also over some known buildings.

Location of GPR survey undertaken in February 2014.

Location of GPR survey undertaken in February 2014.

The next and long sequence of images show the mag data on its own, and then each of six time slices.  These represent increasing depth although at present all I know is time going from 8 to 32 nanoseconds (ns) in 4 ns slices.

Foerster magnetometer results in the area where the GPR survey was undertaken, February 2014.

Foerster magnetometer results in the area where the GPR survey was undertaken, February 2014.

Time slice for 8-12ns.

Time slice for 8-12ns.

Time slice for 12-16ns.

Time slice for 12-16ns.

Time slice for 16-20ns.

Time slice for 16-20ns.

Time slide for 20-24ns.

Time slice for 20-24ns.

Time slice for 24-28ns.

Time slice for 24-28ns.

Time slice for 28-32ns.

Time slice for 28-32ns.

As can be seen we have some beautifully clear buildings including one which overlies the 1955 ditch.  We also seem to have a road inside the 1955 ditch which I haven’t seen postulated on maps of Verulamium.   One of the many questions which comes to mind is whether the big rectangular area to the west of the plots is only the result of the cricket wickets or is there an underlying building as well?

Just to finish I include one last graph showing the single 20x20m resistance data plot on the GPR data.  There is excellent agreement.  Given how utterly saturated the ground is I am surprised anything shows, but the results are OK, if not stunning.  The dark band is probably the road which runs to the south of the 1955 ditch which has been seen before.

Resistance data overlain on the GPR and magnetometry data.

Resistance data overlain on the GPR and magnetometry data.

Next week we’ll be out again working under the trees to finish off the last few bits.

Heading South

We have managed another three days of survey despite the rain and have made good progress along the southern edge and around the cricket pitches.  As you can see from the first image below, there isn’t a great more left to do.  A few grid squares near the London Gate, and whatever we can manage in the trees towards the ramparts.  I recently discovered that English Heritage did a magnetometry and resistance survey along the back of the ramparts in 1994 which gives us some interesting comparative data.

The most obvious feature is the bend in the 1955 ditch which we have picked up nicely.  The elegant curve between the two straight sides of the ditch is a credit to the Roman surveyors who laid out this important early feature.

The survey of the southern area as of February 9th 2014.

The survey of the southern area as of February 9th 2014.

The majority of the interesting features, however, have come up along the new line of grid squares at the south of our plot.  In the second image below I have labelled a few items.  We have one very clear building with four or maybe five rooms.  There are also tentative hints of a much larger building possibly with a courtyard.  There are also a number of very magnetic features which are possibly industrial features such as pottery kilns.  I have labelled one “key hole” shaped feature which is a likely candidate.

Some of the features along the southern edge of the survey as of Feb 9th 2014.

Some of the features along the southern edge of the survey as of Feb 9th 2014.

Lastly, there is a curious group of features just to the west of Watling Street and north of the London Gate (see below).  There is a clear linear feature with a nice rounded corner forming a right angle, almost certainly a ditch.  Slightly to the east where that feature fades a little is a line of positive anomalies which could be a series of large pits.  Before jumping to conclusions I need to consult a little more widely but these features could be rather important.

Features near the London Gate as of 9th Feb 2014.

Features near the London Gate as of 9th Feb 2014.

We will be running a short course for UCL masters students on February 17th and 18th in this general area.  Do come along and say hello, or even lend a hand!

As always, many thanks to our stalwart volunteers who have turned out in the wind and rain showers to make this all possible.

The final day?

Yesterday was the last day of the funded phase of the project.  Looking back I think we can be proud of what we have achieved.  The course was a success, the surveys have been great and we have almost finished Verulamium…  Sadly, “almost” finished.  The rain on Wednesday and Thursday kept us all away (apart from Jim and his tablet, but more on that in another post) but we had a fantastic turn out on Friday, many thanks to everyone who turned out.  We managed seven “fields” (i.e., grids, partial or otherwise) before the rain started at 1pm and drove us away.

The south-west corner of the survey area as of 31st January 2014.

The south-west corner of the survey area as of 31st January 2014.

Sarah Poppy, Assistant Inspector of Ancient Monuments for the region, kindly agreed to give us an extension to the Section 42 licence so we can finish what we began.  We’ll be out tomorrow (Sunday) working our way west to east along the southern edge of the town.  The weather forecast is good, so fingers crossed for a successful day.

What about the future?  There is lots to do.  We have to write-up the surveys we have conducted including making the overlays and, of course, keep on surveying.  It would be excellent to survey more smaller sites to add to those we have completed but any cultivated fields are impassible at the moment given the rain we have had.  Fingers crossed we have a window of opportunity between the fields drying out a bit (if they ever do!) and the crops getting too tall to walk on.

More postings and information to come, so keep an eye on the blog.

Long time no post

Apologies to you all —  blog followers and the volunteers who have been out surveying — that it is such a long time since the last post.  We have been very active trying to get Verulamium Park completed before the end of the grant and the licence in five days time.  We are very close to hitting that target as you can see below.  The short days, wet weather and endless fiddly partial grid squares slowed us down a great deal.  We have, however, only a little bit to complete in the south-west corner, and a few little bits along the southern edge and we have done the whole Park.

The total area surveyed as of January 25th 2014.

The total area surveyed as of January 25th 2014.

I haven’t quite finished the data processing as there were a huge number of fiddly grid squares to edit, but I decided it was best to get something out even if not finished.

The area south of the splash park and around the cafe has some interesting features.  Some of the roads show every clearly and there is a very clear stone building just to the east of the cafe.  Interesting to note that this is just the other side of the road from the building Larry Conyers picked up so clearly in the GPR data in the summer, whereas that building barely shows at all.

The survey around the cafe, the splash park and the museum car park as of 25th January 2014.

The survey around the cafe, the splash park and the museum car park as of 25th January 2014.

The area surveyed by Ralph Potter in the summer to the SE of the car park is as inconclusive in the mag data as the GPR data.  I’m not sure what has happened here.  Another question to investigate.

There is a long field along the side of Bluehouse Hill which during the summer is the “wild flower” area.  Luckily for us, the grass is cut short over winter and during December and January we have been working our way along this strip.  In the northern area (see below) we have picked up a couple of stone buildings either side of the SW-NE road which eventually runs alongside the SE edge of the forum-basilica complex now under the church and the school. The “Romano-Celtic” temple, which often shows clearly as parch marks, doesn’t show in the magnetic data at all.  There are a couple of processing artefacts which need to be corrected, mainly the lighter white square in the middle of the plot.

The northern end of the wild flower area next to Bluehouse Hill as of Jan 25th 2014.

The northern end of the wild flower area next to Bluehouse Hill as of Jan 25th 2014.

Lastly, the southern end of the wild flower area is very similar to the field we started surveying at the beginning.  There are few indications of major buildings, but the 1955 ditch shows, quite a few probable pits and some linear features, almost certainly ditches, some of which can see be seen on the surface.  Unlike the SE corner, however, the Roman wall shows very clearly running diagonally across the SW corner of the image.

The southern end of the wild flower area as of the 25th Jan 2014.

The southern end of the wild flower area as of the 25th Jan 2014.

I hope these excellent results were worth the wait, and fingers crossed we manage the last few parts this week.