Anyone new to this blog or geophysics in archaeology is recommended to read the material on the “Geophysical survey in archaeology” page.
Week three started well with all three machines collecting data. The Earth Resistance survey was the poor cousin as regards person-power but Ellen and I, helped by Rhian, completed three grid squares after lunch.
Figure 1: Ellen and an earth resistance meter.
The grids are over the fascinating burnt building seen in the mag. Figure 2 shows the mag data in this area.
Figure 2: the mag data in the area of the res survey.
The black line snaking across Figure 2 from top-left to bottom-right is the aqueduct. The very bright black-and-white area in the NW corner of that figure is probably a burnt building which was never replaced in stone. Figure 3 shows the Earth Resistance data.
Figure 2: the Earth Resistance data.
Figure 3 is a crude composite of the data collected in 2016, 2017 and 2018. The three squares at the north edge are this year’s grids. We have clearly picked-up a long wall running NW-SE, and some square areas of higher resistance (?floors, maybe). This survey makes an interesting comparison to the GPR in this area (Figure 4).
Figure 4: the GPR survey in the same area as Figures 1 and 2.
There is a lot of work to do tracing off walls and features from the three surveys.
The GPR crew completed another 80x40m block, although the slope was quite a challenge. Figure 5 shows the time slices.
Figure 5: day 11 GPR time slices.
Slices 4 and 5 (top-right and middle left) seem the most interesting. No stunningly clear buildings but lots going on. Figures 6 and 7 compare the fifth slice with the mag data.
Figure 6: Fifth time slice from day 11 (indicated by the purple line).
Figure 7: the mag data in the area of the day 11 GPR data (shown by the purple box).
Notice how the square of higher mag response shown in darker tones towards the bottom of the purple rectangle are an area of light “low reflections” in the GPR data. It is possibly something like an earth floor? Off the west corner of that square in the mag data is a lighter coloured line running to the SW which is matched by a black line of high reflections in the GPR data. That is clearly a wall, probably made of flint. The very narrow section of the aqueduct which runs east-west across the plot shows very clearly in the GPR data whereas the broader sections do not. Something odd happens with the aqueduct at the eastern edge of the GPR plot. A great deal more to tease out.
One problem we have had this year is the sheep. In general they keep away from us. The main issue is that some of them think the flags are tasty… (Figure 8).
Figure 8: Tasty! A nibbled flag in Mobbs Hole with the mag crew in the background.
The mag crew consisting of Jim West, Peter Alley and Dave Minty had three annoying partials to do before marching eastwards across the field. I’m afraid I have not finished processing those annoying squares but I have added in the complete ones to Figure 9 so you can see progress.
Figure 9: mag data in Mobbs Hole after day 11.
Unfortunately, today was a bust as it rained 8.5mm. The forecast for tomorrow is looking good though.