Extraction of buildings from QuickBird imagery for municipal planning purposes: quality assessment considering existing mapping standards

Abstract

Many municipal activities require updated large-scale maps that include both topographic and thematic information. For this purpose, the efficient use of very high spatial resolution (VHR) satellite imagery suggests the development of approaches that enable a timely discrimination, counting and delineation of urban elements according to legal technical specifications and quality standards. Therefore, the nature of this data source and expanding range of applications calls for additional methods and metrics to assess the quality of the extracted information which go beyond traditional thematic accuracy alone. The present work concerns the feasibility of VHR satellite imagery as an alternative source of geospatial information for large scale mapping to assist urban planning in Portugal. Feature extraction software was employed to map buildings present in a pansharpened QuickBird image of Lisbon. Quality assessment was exhaustive and involved comparisons of extracted features against a reference dataset, introducing cartographic constraints from scales 1:1000, 1:5000, and 1:10000. The spatial data quality elements subject to evaluation were: thematic (attribute) accuracy, completeness, and geometric quality based on planimetric deviation from the reference. Tests were developed and metrics analyzed considering thresholds and standards for the different mapping scales most used by municipalities. Results show that values for completeness varied with mapping scales and results were only slightly better for scale 1:10000. Concerning the geometric quality, a large percentage of extracted features met the strict topographic standards of planimetric deviation for scale 1:10000, while no buildings were compliant with the specification for scale 1:1000.