Further to my previous post, I have now had another go at constructing trend surfaces for the four broad main periods covered by this project. This time, however, I have filtered out records that are explicitly related only to artefact findspots (for each period). This was in an attempt to downplay the influence in the previous trends from differential inclusion of PAS material between HERs. The remaining records should, hopefully, thus primarily relate to sites with other archaeological evidence beyond just one or more artefacts.
Here are the results (to the same attribute scale as previous):
Comparing to the previous surfaces, we can see a general reduction in trend peaks, especially over Norfolk and Yorkshire. The Bronze Age remains similar to previous; the Iron Age also, albeit with much lower peaks; the Roman period shows an increasing strength across Gloucestershire; the early medieval shows the most distinct reductions in eastern regions.