Assessing ground conditions of small sites by aerial infrared photography

Abstract

The false-colour infrared photograph of Lightmoor Tip in the Forest of Dean, Gloucestershire (Fig. 1) was taken using a radio controlled camera plane. The tip is associated with past coal extraction from the Carboniferous Limestone. In this example, infrared and natural colour aerial photography were used to determine topographical and subsurface information. Geomorphological and ecological processes have created various microenvironments at the site. The majority of the soil supports vegetation. The aerial infrared photograph shows not only the major plant communities, but also their health and relative densities. Dark red to dark pink areas correspond to healthy, dense growths of vegetation, whilst colour tones of pink and grey depict poor or stressed vegetation. Exposed substrates and routeways appear greenish blue to light grey. Increased amounts of surface moisture result in darkening of ground colours. A short grass community forms the initial colonizer of the tip and dominates the site. Grass health is poor on steep slopes, particularly over rock and scree debris, where vegetation is absent in places. Notably healthy, dense growths of grass are visible in zones where there may be water collection or seepage. A second natural community, consisting of gorse and low shrubs, is present on more sheltered and gentle slopes. The majority of this vegetation is thin and in poor health. Development from the short grass to scrub vegetation has progressed where the slopes are stable. The configurations of these slopes and nature of the vegetation would suggest that they represent older scree debris. Figure 2