DIGITAL ENHANCEMENT AS AN AID TO DETECTING PATTERNS OF VEGETATION STRESS USING MEDIUM-SCALE AERIAL-PHOTOGRAPHY

The application of image processing algorithms, originally developed for satellite image analysis, has been shown to improve pattern recognition of environmental change and vegetation stress with medium-scale aerial photography. Image enhancement helps to identify subtle features and spatial patterns embedded in a digitized air photo transparency that might otherwise escape visual identification. Our procedure combines visual interpretation with computer-aided image enhancement, including Normalized Difference Vegetation Index (NDVI) and supervised and unsupervised classification. The motiviation for the application of these techniques came from the need to provide a multi-season record of environmental changes in the immediate vicinity of power generation facilities. The procedure involves simple, on-call, acquisition of colour infrared and colour aerial photography that can be electronically enhanced and evaluated, resulting in accurate, timely, and cost-efficient information on vegetation changes related to land management, weather, diseases, insects, or other environmental stressors.