LIDAR-derived DTM for archaeology and

landscape history research some recent

experiences with QGIS and GRASS

David Lovelace

david@tilia.org.uk

@boscinet

Using the newly (Sept 2015) released EA LIDAR-

derived DTM. First, merge your 1 km squares

Apply colour styles to the merged

DTM showing height gradations

To display the subtle variations of earthworks

of possible archaeological interest we need

something more sophisticated: GRASS

GRASS has a large number of libraries for most raster

(and vector) operations anyone can think of. Here I’m

using r.slope.aspect which generates new raster using a

variety of surface differential maths operations

Using GDAL from the command line (for Windows useg the msys.exe shell) is

another option – Here are a couple of examples where I’m using the Python library

gdal_calc.py to generate a new DTM by exaggerating the surface differential from

the GRASS r.slope.aspect operation and adding it the original DTM so revealing the

‘ridge and furrow’ and other earthwork features in the Bartonsham meadows:

Raster OS 1:25,000Air photo Bing 2012Result of the GDAL command line processingOverlay of geo-referenced 1st edition 25” to mile c1880 OS map Processed DTM layer and partial transparency of 1880 OS map Overlay of the 1840 tithe map (G. Gwatkins annotated version) Buildings vector layer overlaying the coloured processed DTM 20 cm contours (note the ridge & furrow) – see next slide but one Effect of clipping the DTM raster with vector outline of AOI

Effect of the QGIS3js Plugin

Moorcourt Estate proposed list parkland – water meadow carrier

Control of DTM shadowing using

the Terrain Analysis plugin

EA 2m DTM horizontal resolutionDNP 25cm DTM horizontal resolutionDNP 25 cm DTM differential

David Lovelace

david@tilia.org.uk

@boscinet