LiDAR, Local Relief Models and Sketchfab

Archaeogeomancy: Digital Heritage Specialists – archaeological geomatics – the majick of spatial data in archaeology – archaeological information systems for the digital age:

Cranbrook Castle; LiDAR based Digital Terrain Model (DTM)

Cranbrook Castle; LiDAR based Digital Terrain Model (DTM)

The following visualisations were produced as part of the Fingle Woods and Castle Drogo Aerial Survey Analysis and Interpretation project, recently completed for the National Trust. There is a visualisation for each hillfort in the study area: Prestonbury Castle, Wooston Castle and Cranbrook Castle.

The visualisations were produced from a Digital Terrain Model (DTM) based on LiDAR data provided by Bluesky at 25cm resolution. This DTM was also used to produce a Local Relief Model using one of the ArcGIS tools currently being developed by Archaeogeomancy for the National Trust. The LRM was then draped over the DTM, exported as VRML and uploaded to Sketchfab.

One of the issues with using traditional forms of GIS symbology for representing hillforts is that they are typically, as the name suggests, situated on hills. Any colour ramps used and/or statistical means of distributing the range of elevation values are therefore adversely affected by the rather large range of elevation values present, with the interesting values (ie the heights of the earthworks) being somewhat lost in the overall distribution, as shown in the image above.

This is where LRM is a great tool as it ‘normalises’ the elevation values using the underlying topographic trend; in other words, LRM removes the natural shape of the landscape leaving only the smaller deviations which include all the lovely archaeological features of interest.

Combining this with a 3D Digital Surface Model (DSM) on which to drape the LRM gives a very useful product which includes the overall landscape form for context but through the LRM focusses on the archaeological features. Sketchfab is a great platform for sharing such 3D visualisations of sites and monuments as well as pretty much anything else 3D from landscapes to artefacts or architectural features.

References:

Hesse, R. 2010 ‘LIDAR-derived Local Relief Models – a new tool for archaeological prospection’, Archaeological Prospection 18, 67-72

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