Comparison of spatial information recorded over the same area at different times to detect changes in the features of interest.
Change detection is a particular application of Earth observation in which data integration is required before one can concentrate on the observable changes. In change detection, there are different kind of change to be distinguished.
This section will focus on how data integration is applied in change detection. We will focus on changes on the surface of the Earth, but there is certainly an overlap with the techniques used in other image processing sciences, like medical imaging.
Changes are caused by processes. These processes can be natural, man-made, sea-sonal, deterministic or random. To determine appropriate data sources for detect-ing change, several characteristics of the process need to be known, such as speed, duration, observables, area coverage and seasonality. Data selection criteria and Data integration with its Figure on Earth Observation variables and their meaning for users explain how these characteristics can be used to determine spatial and temporal coverage, time and frequency of observation, spatial resolution or scale, and observables. The expected size of the change determines the degree of sensitivity needed in the analysis.
Change detection can be carried out at various levels of detail or sophistication, de-pending on the interests of the user. This may include answering some or all of the following questions: