Time series aerial photographs to detect spatio-temporal changes in coastal areas of Fiji

Abstract

Time series of aerial photographs, which are reasonably widely available in the Pacific Island countries, provide a useful resource of geospatial data and can be used for the detection and quantitative assessment of spatio-temporal changes in the most dynamic coastal areas, which are often economically and culturally valuable, but also vulnerable to the effects of natural and anthropogenic stresses. Quantitative analysis, based on GIS and advanced image processing, is the most precise but time-consuming method. In many cases, visual detection and preliminary assessment of changes is a rational way to decide quickly whether more sophisticated techniques should be employed to map spatial changes in more detail. This paper elaborates on different techniques available for rapid change detection and analysis using time series of aerial photographs. The rationale and applicability of such methods are illustrated in a feasibility study that was implemented to detect changes since the mid-1960s in mangrove cover in the Korotogo area of the Coral Coast, on the southern coast of the main island of Fiji.