Kite aerial photography : A low cost remote sensing tool for ecological research?

Remote sensing and GIS software is increasingly used in ecological research. Although there is a lot of imagery readily available from different suppliers, the spatial or temporal resolution often don't match the researchers need. Kite aerial photography can be used as a simple low cost remote sensing tool. In this research, kite aerial photographs are taken from a small nature reserve in the east of the Netherlands, 'de Borkeld' (lat,Ion: 52.271265°, 6.491023°). The camera used was a normal consumer digital camera (Canon s70). For use in photogrammetic applications the camera had to be calibrated. The focal length, pixel size on the ccd, principal point and lens distortion were determined using Photomodeler 5. Before the aerial photographs were taken a grid of markers was placed in the study area and their positions and elevation was recorded with a geodetic dGPS. These markers served as ground control points in the georeferencing process. From 16 aerial photographs a mosaic was created covering 16.9 hectares. The mosaic has a ground resolution of 8.7 cm. From a subsection of the mosaic area a highly detailed digital terrain model was constructed. Using a supervised classification a vegetation map with 5 classes was created. The high resolution of the images gave some problems for the applied classification method. Due to variations in light and shadow, some misclassifications occurred. However the overall result was good. Especially Molinia caerulea, a species that replaces the heather vegetation, had a distinct spectral signature and was easy to identify. The heather coverage mainly consisted of Calluna vulgaris with some patches of Erica tetralix. By clipping out the heather area from the main image a supervised classification was done using only two classes; Calluna vulgaris and Erica tetralix. Using this method the patches with Erica tetralix could be predicted with high accuracy. Using kite aerial photography and normal digital cameras for photogrammetic purposes in ecological research shows great potential as a research tool. With the ongoing development of digital camera's and GIS software this method provides a way for researchers to obtain their own aerial images.