Ashby Puerorum

This rather nice cropmark plot appeared in Bewley 1998 Lincolnshire's Archaeology from the Air. Rather less helpfully, it appeared unadorned by anything as useful as NGR reference points (let alone base mapping). It is at least at a handy 1:25000 and individual cropmark complexes are provided with six-figure grid references elsewhere in the volume, so we have somewhere to start. Beyond that it's trying to spot places where the pattern is interrupted by a road line or block of woodland (the cropmarks just north of Bag Enderby do the trick) so as to position them with some confidence (even if only at this small scale). Why? Well, there may be some work on the site at Ashby Puerorum in the northwest corner. Bulldozed in the 1980s to produce embanked stock compounds the question is what, if anything, survives?

ASTER + Landsat = Dacia

Up to now I have tended to work with SRTM data for small-medium scale topographic mapping (the topographic base I use for all my UK regional maps starts from there).  It was always somewhat annoying that the rest-of-the-world dataset was less detailed than that available for the US... which is where ASTER comes in. Version 2 of the dataset has been out for over a year now and I must admit its taken me this long to really get round to looking at it. I like what I see. [But in some lower relief areas - and particularly the UK - it leaves a lot to be desired. Really no better than SRTM - see the useful comments here.]

The above uses ASTER elevation data for topographic mapping with a Landsat overlay to give some realistic colouration. The approach routes of the Roman armies to the Dacian fortress at Sarmizegetusa are taken from Stefan 1998. The grid squares are 5km.

Roman Roads

Just quickly. Looking at the downloads available from the Ancient World Mapping Centre (those nice people behind the Barrington Atlas). The above easily created by dropping their Roman roads shape file onto a base map of Europe (very old, using Digital Chart of the World elevation polygons - vector data [hurrah!] - but broken down by country which made stitching the lot together rather painful).

Swineshead Abbey

A slight departure. The idea behind the Lincolnshire Fenland Lidar project was to produce seamless mapping at all scales, from that A0 poster on my wall down to the best resolution that 2m lidar can offer (about 1:5000 in my experience). I still feel the chosen colour ramp works well, but it represents a compromise and individual sites are certainly worth revisiting. This image is of Swineshead Abbey (occupying higher ground slightly south of centre), with the motte and bailey castle Manwar Ings just to the NW. Starting with Environment Agency data as usual, but seeing what SAGA GIS will do for us. I have wondered if the abbey wasn't sitting on a watercourse with access to the sea. Some of the sinuous channel forms here reinforce that idea.

Mapping Legio XX Valeria Victrix

This is something of a crossover post. Recent effort in mapping has gone into mastering (by which I mean 'knowing just enough to make it do what I want in this particular instance') v.3 of the Googlemaps API. The aim has been to map locations of the inscriptions of soldiers of the Twentieth Legion. Now up and running. You can see more here.

Pretty standard piece of mapping really, but enough changes from the last time I did it (probably version 1) to have me scratching my head from time time. Getting the database xml formatting right (and the html formatting inside the xml) was half the battle.

Plenty still wrong with it. I don't really need all those layer options. Watercolour is quite fun the first time, but really the Imperium tile set created by the Pelagios Project is my preferred option. Too many coincident points at some places (eg Chester!) for this to truly work; some inscriptions refer to people known from other sources to have served with the legion and are not particularly informative in themselves; I will find a better marker symbol eventually (or revert to something standardised)... but for now it does demonstrate the geographical range of the dataset reasonably well.

Roman Empire

This derives from one of a series of marble maps alongside the Via dei Foro Imperio in Rome. Set up in 1912 and now somewhat discoloured and stained, this version has been photoshopped back into something approaching a pristine state (at least within the borders of the Empire). Original labelling is in Italian (Germanico anyone?), so I’ve removed that as well. I like the (authentically) 3D coastline effect and have used it as a basemap (and talking point) in presentations. This purports to show the empire at its greatest extent under Trajan, although the province of Mesopotamia was a very temporary addition. The sites of Kalkreise and Kalefeld (orange) and forts at Laugaricio and Balklava (red) indicate some of the range of earlier and later activity well beyond this border.

The projection appears to be Lambert Conformal, more or less, but my perspective corrections to the upward viewpoint of the original photo have probably distorted this somewhat, so I don’t get a precise fit. Still, most things drop into place pretty well and reprojection (as here to Miller Cylindrical) have an intruiging effect.

Lidar visualisation 2

Taking that last map of slope severity and draping it over a 3D surface model. Some things certainly more evident. I hadn't noticed the hollow way ascending the slope in the bottom left previously; earthworks below the woods in the bottom of the valley; still wonder what to make of the mounds on the far hillside. This produced using SAGA GIS which I'm more impressed with the more I get to grips with its capabilities.