Integrating aerial videography and digital photography with terrain modelling: an application for coastal geomorphology

Abstract

The integration of airborne imagery, derived from video and digital camera imagery, with terrain data from ground survey is within the scope of low-budget, small scale geomorphological investigations. Geographical Information Systems (GIS), available on standard desktop computer systems, are suitable for the integration of this imagery with other geomorphological survey data. Different georeferenced datasets can be combined to produce visualisations that can aid interpretation and measurement that may otherwise be difficult to achieve. As with all remote-sensed data, the synoptic view has considerable benefits, especially when combined with ground fieldwork. There are a variety of methods that can be used to collect and process these data dependent upon the aims of the geomorphologist. There is always a trade-off involving the cost, spatial resolution and temporal control for each of these methods, and this trade-off ultimately determines the absolute accuracy and suitability of the imagery for the purposes required. Although it always seems desirable to attempt to collect the highest resolution imagery possible, using the greatest degree of control and results that can enhance the value of standard field techniques. Decisions involving choice of capture equipment, methods of processing, methods of establishing position and attitude, and ground control techniques determine the quality of the imagery produced. The rectified imagery, when combined with digital terrain models, significantly aids the interpretative process and enables features with boundaries visible on the ground to be delimited on the terrain model and related to contour plots. Airborne video is a cheap, easily available and flexible method of producing this imagery. Recent advances in digital techniques have resulted in digital video and digital camera photography becoming alternatives to conventional video. The advantage of using a digital format is that the number of processing steps is reduced with potential savings in equipment, cost and time as well as improvements in resolution and accuracy. Digital camera photography shows particular promise with spectacular improvements in image resolution and continually falling costs making it an increasingly viable alternative to standard photographic film, particularly when the data are to be transferred onto a computer system. The accuracy and resolution that can be obtained are superior to those obtainable from orbiting systems and future availability of sensors covering a variety of bandwidths will enable multi-spectral analysis. The combination of this kind of imagery with terrain data is a powerful one, either for data visualisation and interpretation or for feature definition and measurement of change.