With that many historic maps, why dig holes? Treasured Islands! Episode 2, Day 3

It’s Sunday, and I’ve got the day off, leaving Justin and Robert to clean up the trenches we’ve got opened so far.

So that’s an opportunity to take a step back and talk about the results of the survey work done in July. The measured survey didn’t turn up any vast surprises, but it did create a completely accurate base map which we can use in all of our future works. Everyone thinks of Ordnance Survey maps as gospel truth, but in reality their precision varies considerably. The most accurate surveys are those of the first edition 6 inches to the mile survey, and the first edition 25 inch maps – which in Studley’s case were published in 1854 (surveyed 1848-52) and 1891 respectively. Both were completed after the site had been recorded by surveyors, whereas other editions drew on earlier sources for at least parts of their depictions. Even modern digital OS data is less precise, in some regards, than the first edition maps.

What the July survey gave us that we didn’t have before, were detailed contours of the site. These weren’t enormously illuminating, but were useful in confirming that the islands and the ponds hadn’t left any obvious surface traces (although the evidence did highlight inconsistencies in the location of the Quebec Monument, that we’re now keen to explore). So we could be sure that there was no other, better, evidence on which to base the location of our excavations than the historic maps (including the estate maps of 1831, 1838, and 1870 as well as the OS editions).

Using fixed points on our new survey, we were able to digitise the different historic map depictions of pond and islands and put them all on the same plan for the first time.

So much for all appearing to show us the same picture! As you’ll see from the image posted with this mailing, when looked at in detail the different depictions hardly correspond at all. A major objective of the excavations will be to try and determine which of the depictions is the most accurate, and another to establish whether there is any clear physical cause for so much variation in the course of just 60 years or so.

The trenches we planned to excavate are marked as red blocks on the illustration. As you’ll see, they cross the majority of the depictions of the edges of the ponds and islands, and so should pick up some sort of traces of whichever is the most accurate. Some of the southern trenches have had to be relocated, as I mentioned yesterday, and the most south-easterly one had encountered an unsuspected concrete track just beneath the surface. We’ll relocate it to hit less disturbed ground, when we’re back with the digger to finish the mechanical excavation on Tuesday.