John Pitchford's Witham

John Pitchford's 1733 map of the course of the River Witham from Lincoln to Boston, produced at a scale of 2 and a half inches to the mile (1:25,344), unfortunately does not survive. This version 'correctly reduced and drawn from the original' in 1734 is at nearer 1:80000. Nonetheless, a very accurate piece of survey for its day. It shows the route of the river prior to improvements in the 1870s. Neither of the Projected Cuts laid out here were ever undertaken, the final scheme taking a route inbetween the two. The map is overlain onto a lidar map produced from Environment Agency data showing the detailed topography of the valley and the Witham fens and the course of the prehistoric estuarine river.

Maryport lidar

Lidar from the usual source (EA). Slope severity plot looking NE, showing the setting of the Roman fort at Maryport very well.

Here, looking in much the same direction, a sky-view-factor plot showing the impressive detail of the surviving earthworks. Excavations have been ongoing for a year or two. Plenty there to go at.

Caerwent

The smaller scale image doesn't really do this justice. This is extracted from Environment Agency 0.25m centred lidar survey data. Not much UK coverage at this scale, mostly very tightly focused on coastal zones and river valleys, but they do happen to have covered the site of Venta Silurum. The detail of the wall circuit and bastions, and of exposed Roman building foundations within the town, is quite amazing (for what is, essentially, an off-the-shelf product).

Here, the same expressed as a sky-view factor plot and viewed as a 3D model from the south-west.

Old Sarum

The Iron Age hillfort and later motte (and cathedral) at Old Sarum, just north of Salisbury, Wiltshire. Environment Agency 0.5m-centred data (this stuff is starting to get impressively detailed) expressed as a sky view factor map with colour ramp.

And the sky-view-factor plot viewed from the NW as a 3D model.

Viroconium

 

Next in our tour of Roman sites (once more courtesy of Environment Agency lidar): Wroxeter, Viroconium. The overlay of the layout of the town is from Wacher's Towns of Roman Britain, so not the most up-to-date plan by any means, but it will do to be going on with.

Durobrivae - Credenhill - Kenchester

Three lidar images at the same scale: Durobrivae, Credenhill hill fort in Herfordshire and the site of the Roman town at Kenchester a few kilometres to the south. Data courtesy of the Environment Agency again.

Durobrivae lidar

Environment Agency lidar data is now freely available for non-commercial use, so I have been setting about making use of it (after jumping through a few hoops to establish my non-commercial credentials in this instance). Roman town sites are the order of the day, particularly green-field sites, as in this instance at Chesterton/Water Newton (Durobrivae). The site of the town and its defences are very evident in the survey, with the route of Ermine Street through the town to the river crossing and beyond especially clear. Dropping the cropmark plot over the top goes to show how much lidar survey can aid understanding of landscape setting (quite apart from its mapping of earthwork features). The site of the palatial complex at Castor lies towards the northern edge of the map (to be added later).