Anyone new to this blog or geophysics in archaeology is recommended to read the material on the “Geophysical survey in archaeology” page.
Today saw another good sized block of GPR data collected and another six 20x20m grid squares of Earth Resistance data. I skived off to give a talk at Verulamium Museum (and welcome to anyone visiting the blog for the first time having heard my lecture!).
Today’s results saw the GPR and Earth Resistance meter swap roles, in the sense that the Resistance data, although good data, showed very little but the GPR picked-up some spectacular buildings on the ridge. First the resistance data.
We have picked up the road as a very solid linear feature just north of the hedge line that bisects the theatre field. Then it stops. Hmmmmm. It stops where there is a slight dry valley. Robbing? Erosion? Or just never that solid at that point? The high-pass filtered data is not much help in this case.
The difference between the upper and lower halves of the plot are just differences in processing between last year’s survey and this years. At the end of the season I’ll join the two together and attempt to make the two seasons match. For completeness, here is the mag data.
Now to the GPR data. The team collected a 57x40m block, and then a “sawtooth” section along the hedge line. The new software produces a map of the lines so one can check that they have been set-up correctly in the program.
The initial processing showed some clear buildings, but which colour scheme to choose? Here is a selection with the sixth slice.
Whichever colour scheme you favour, the busy line of buildings on the western edge are very clear. Fig. 6 shows the six most informative slices.
There is a road running across the NW corner of the plot, with multiple buildings alongside it. Quite an impressive set of rooms and corridors. In the middle of the plot there appears to be a partially surviving structure close to the fence line. Slice 6 is the most informative, so Fig. 7 shows it in context.
The last image (Fig. 8) shows the mag data from the same area.
The large high contrast black and white blob in the corner of the mag plot is a metal water trough. The buildings along the road show quite well, but the GPR plot provides more detail.
Many thanks to Ellen, Pauline, Graham, Nigel, Mike and Jim for all their efforts today. Tomorrow, the res will continue to work westwards, whereas the GPR is heading back to the depth south at the top of the hill.