Lidar for free!

As of the beginning of this month all of the Environment Agency Lidar data for England has been released as open data. It can be accessed through a new portal. Some have complained of problems, and it can be rather slow loading the background mapping, but I've been able to get my hands on lots of interesting stuff already.

Roman temporary camps north and south of Hadrian's Wall just east of Aesica

The data is released under Open Government licence which allows commercial use, so it's all there to play with as you see fit. Sadly, in the process we have lost Wales which devolves elsewhere (though through some odd [and yet to be repeated] glitch I managed to download a chunk of the Lleyn peninsula just the other day, so the data seems to be there - hopefully someone will sign it off for release before too long).

Burrough Hill Lidar

I was surprised to see EA data at 0.5m centres available for this seemingly random block of Leicestershire countryside until I noticed this. So presumably this derives from the survey commissioned by the University of Leicester, although point density may have been somewhat higher in the original surveys to judge by that nice de-vegetated bare-earth model. Pleasing results from this nonetheless.

The first image is a slope severity plot; the perspective view from the south-west is based on a sky-view factor plot.

Grey Ditch

A blast from the past (but which may become more relevant again in future). Looking south(ish) towards Bradwell from the Hope Valley in Derbyshire. The dark age earthwork Grey Ditch runs across the valley from the left-hand skyline, down across the lower slopes and across the line of the Roman road towards Mich Low on the right hand edge of this view (and probably continuing to cut off the hill saddle just behind). Spent a lot of time in these fields recording the earthwork in detail with EDM (in another life). If I can find the files somewhere, I'll post a comparison (this is from Environment Agency 2m-centred lidar, so the effort with the EDM isn't wasted, yet!).

Haiwarde 1595 and lidar

Above, a lidar plot from EA data of the Lincolnshire Marsh at Marshchapel showing extensive remains of medieval salt production. Below, the same plot overlain with William Haiwarde's 1595 map of the parish demonstrating the remarkable accuracy of this early mapping (although it has taken a little work in QGIS to make it fit quite this well). Almost as remarkable as his very accurate depiction of the shape of the salterns is the fact that they retain that recognisable shape to this day. At the time of his survey Haiwarde depicted small structures (salt cotes) on the most easterly of the salterns, but these were clearly the last active salterns for no more have been developed beyond these after 1595.

Birdoswald lidar

The Roman fort at Birdoswald on Hadrian's Wall sitting high above the steep-sided (and eroding) valley of the River Irthing. The wall itself attaches to the northern corners of the fort running eastwards to a mile-castle just before the steep descent to the river. The Vallum appears at the west of the plot with (intriguing) earthworks just to the north. Sky-view factor plot using EA 1m-centred data.

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.

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.

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.

Great Steeping and Firsby

Lidar plot of Great Steeping and Firsby on the northern margins of East Fen. Well-preserved medieval earthworks in and around the villages. Broader headlands (baulks?) evident more widely where the ridge and furrow is ploughed out, usual EA data source.

Apropos of nothing particular. Just the result of an afternoon spent realising that my pre-MapInfo 9 workaround (so that's going back quite a way) produced some nasty data holes (well, the data holes were already there, they just end up looking more obvious). Easily solved. Just adds something more to the to-do list.

Derwent Valley - Little Eaton

This is a Lidar plot of part of the Derwent Valley just north of the city of Derby at Little Eaton produced with Environment Agency data. I've just dug this out for a potential upcoming project. It was created for an external client some time back (to be honest I can't entirely recall for what purpose). Downstream is the site of the Roman fort at Littlechester, of which I probably do have an image somewhere. Here we see the river channels and levees of the Derwent and surviving areas of medieval ridge and furrow.