Detection of partial land cover change associated with the migration of inner-class transitional zones

Post-classification comparison techniques are frequently used in studies of change detection. If the classifications used were derived with the use of conventional 'hard' classification techniques, change detection is constrained to the identification of complete changes in class label. This may be inappropriate in circumstances when the land cover conversion is operating at a scale finer than the spatial resolution of the sensor which acquired the imagery and for the detection of land cover modifications. By basing the change detection on the comparison of fuzzy classifications it should be possible to identify partial changes, including both land cover conversion and modification. Fuzzy classifications of Advanced Very High Resolution Radiometer (AVHRR) data were used to identify changes in the apparent position of the forest-savanna transition in West Africa. A comparison of the classifications revealed the variations in the nature and magnitude of land cover change. It was apparent that the migration of the transitional area could be characterized and showed similarity to a simple hypothesized model of land cover change. The comparison of fuzzy classifications was able to provide a richer information base on class membership and its dynamics than that obtainable through the comparison of conventional 'hard' classifications.