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

The integration of airborne imagery, derived from video and digital camera imagery, with terrain data from ground survey is within the scope of low-bu dget, small scale geomorphological investigations. Geographical Information Systems (GIS), available on standard desktop computer systems, are suitabl e for the integration of this imagery with other geomorphological survey da ta. Different georeferenced datasets can be combined to produce visualisati ons that can aid interpretation and measurement that may otherwise be diffi cult to achieve. As with all remote-sensed data, the synoptic view has cons iderable benefits, especially when combined with ground fieldwork. There ar e a variety of methods that can be used to collect and process these data d ependent upon the aims of the geomorphologist. There is always a trade-off involving the cost, spatial resolution and temporal control for each of the se methods, and this trade-off ultimately determines the absolute accuracy and suitability of the imagery for the purposes required. Although it alway s seems desirable to attempt to collect the highest resolution imagery poss ible, 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 atti tude, and ground control techniques determine the quality of the imagery pr oduced. The rectified imagery, when combined with digital terrain models, s ignificantly aids the interpretative process and enables features with boun daries visible on the ground to be delimited on the terrain model and relat ed to contour plots. Airborne video is a cheap, easily available and flexib le method of producing this imagery. Recent advances in digital techniques have resulted in digital video and digital camera photography becoming alte rnatives to conventional video, The advantage of using a digital format is that the number of processing steps is reduced with potential savings in eq uipment, cost and time as well as improvements in resolution and accuracy. Digital camera photography shows particular promise with spectacular improv ements in image resolution and continually falling costs making it an incre asingly viable alternative to standard photographic film, particularly when the data are to be transferred onto a computer system. The accuracy and re solution that can be obtained are superior to those obtainable from orbitin g systems and future availability of sensors covering a variety of bandwidt hs will enable multi-spectral analysis. The combination of this kind of ima gery with terrain data is a powerful one, either for data visualisation and interpretation or for feature definition and measurement of change. (C) 19 99 Elsevier Science B.V. All rights reserved.