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