I know; the name 'Big Dig' is a bit of a misnomer at the moment because this first weekend in Stroud is all about geophysics. And it nearly didn't happen for technical reasons because of two serious problems with our resistivity machine - more in a minute about that.
First, here are today's results, with resistivity plot first:
This plot is at the eastern end of the villa site. In his comments Carl says "The resistance is very interesting, it clearly shows the [sewage] pipeline heading south from the end of Finchmead lane as well as a very clean-cut low resistance area along the north of the survey area which must be man made. Whether it was cut in recent times or not I cannot say; it could be to do with Moray Williams' excavations or possibly sand extraction."
Then this is the magnetometry plot:
The day started with 12 of us assembling at New Buildings Farm before we headed across the field full of sheep towards the villa site. It took some time to re-establish the grid across the site, marking out the grid squares with plastic canes, so a group of us including two members who had not been at Stroud before explored the fields towards Stroudbridge Farm where we think there might be a trackway and the latest LIDAR and drone images which suggest the route of the track and possibly of the villa's water supply to the baths.
Around coffee break poor Lyn took a fairly spectacular reverse tumble when she caught one of her wellies in the bottom strand of an electric fence as she was climbing over. Fortunately no serious harm done but there will probably be some spectacular bruises in the morning.
I got the new drone airborne to look for parch marks but there were none to be seen; the ground is uniformly very dry, although fortunately the recent occasional showers had made the soil damp enough to permit resistivity.
This image shows our area of operations - the eastern end of the villa site, towards the end of Finchmead Lane. I think that to the right of the above image you can make out the alignment of the sewage pipe that Carl spotted on the resistivity plot.
As seen above, we based ourselves at break time in the lee of the hedges by the double-bend of the stream, because despite the warmth it was surprisingly breezy.
Sneaking up on the 'res' team with the drone.
Peter explaining his theories to Juliet regarding the villa's water supply.
Our biggest issue, and one that threatened to scupper our work, was that Carl found that the charger for the resistivity meter's batteries was overheating and melting last night. We had a charged power pack, but today Carl had to go out and buy sufficient rechargeable NiCad batteries and a charger to enable us to keep going this weekend. Then to cap it all the weld broke that holds the res meter's logging unit on a bracket on top of the steel frame. Fortunately the lovely people at Collyers, in one of the farm's industrial units, kindly gave us a handful of very heavy duty cable ties which you will see in some of the following images were used to hold the resistivity machine together until we can find someone who can weld stainless steel next week. Hopefully fewer tech issues tomorrow!