Object-based approaches to change analysis and thematic map update: challenges and limitations

Bitemporal change analysis strategies performed in an object-based environment are prone to the generation of sliver objects: small, spurious polygons created by the inconsistent delineation of persistent change features appearing in consecutive coregistered images. The issue represents a serious methodological challenge that can limit the visual and structural quality of the finished map product if not adequately addressed. A critical analysis of annual land cover maps generated by updating and backdating object-based reference maps in a western Alberta study area revealed that sliver objects made up between 3% and 12% of the total area of change, and between 63% and 72% of the total number of change objects, despite high thematic accuracies. The results highlight the emerging need for a methodological framework designed to handle the spatial challenges posed by change analysis in an object-based environment.