As I suggested I would in my last post on trend surfaces, I have been experimenting today with constructing individual trend surfaces for the four main broad periods of interest to our project in the NRHE data. I have also been experimenting with some alternative colour schemes after talking to our project artist, Miranda. So, without further ado, here are the logistic presence / absence trend surfaces for the Bronze Age (excluding specifically Early Bronze Age), Iron Age, Roman, and early medieval periods (blue being low likelihood and red being high):
These patterns all look intuitively sensible, albeit with some possible edge effects along the coastlines (as a trend surface becomes more unreliable towards its edges, due to comparative lack of data). To take this further, we can then compare the difference between each surface and its preceding period (not including Bronze Age, as we are not so interested in the Neolithic / EBA):
Again, these results do appear to make sense, with some changes of focus between the Bronze Age and Iron Age (with continuing focus in Wessex), a massive expansion in activity / visibility between the Iron Age and Roman periods, excluding the far north (beyond the Wall) and the south west (with a particular increase in the east of England, north of London), and then a large reduction in activity / visibility across the peak of Roman activity moving into the early medieval.
The next stage would be to start building in data from our other data sources into these models, but that will be something for the future.