Geomorphometry

The geomorphometrics being considered here include a Digital Elevation Model (DEM), Slope, Aspect & Curvature. Prior to calculating the other geomorphometrics, a DEM needs to be created from the LiDAR ground points. This was done using Inverse Distance Weighting (IDW). The DEM itself is presented in Map 2.

Map 2: Digital Elevation Model
Map 2: Digital Elevation Model

Slope was then calculated using the DEM (Figure 3).

Map 3: Slope Map
Map 3: Slope Map

Aspect was calculated from the DEM to visualize which cardinal direction the ground surface faces (Figure 4).

Map 4: Aspect Map
Map 4: Aspect Map

Curvature allows us to see if a surface is convex or concave. This was the last geomorphometric calculated from the DEM (Figure 5).

Map 5: Curvature Map
Map 5: Curvature Map

An additional surface, Principal Component Analysis (PCA), was created from the DEM and hillshades generated from it (Figure 6). This surface was created by generating eight hillshades using the cardinal and inter-cardinal directions at a low angle of incidence and then performing PCA. As such, large amounts of variance are captured within each Principal Component which can then be visualized as one band in a Red, Green & Blue raster image. This is highly useful in observing subtle surface features. This being said, due to the sensitive nature of some surface features, only a low scale image is presented here.

Map 6: Principal Component Analysis
Map 6: Principal Component Analysis

Many of the methods used here to present this data are covered in:
Crutchley, S., and P. Crow. “The light fantastic: Using airborne laser scanning in archeological survey.” English Heritage, Swindon (2009).
Neteler, Markus, and Helena Mitasova. “Open Source GIS: A GRASS GIS Approach. The International Series in Engineering and Computer Science.” (2008): 406.
Additional, credit goes to the workshop, Archaeological Survey Using Airborne Lidar, Crutchley & Crow put together at Oxford University

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