The ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems 2013 (ACM SIGSPATIAL GIS 2013) is the twenty-first event in a series of symposia and workshops that began in 1993 with the aim of bringing together researchers, developers, users, and practitioners in relation to novel systems based on geo-spatial data and knowledge, and fostering interdisciplinary discussions and research in all aspects of geographic information systems. The conference provides a forum for original research contributions covering all conceptual, design, and implementation aspects of geospatial data ranging from applications, user interfaces, and visualization to data storage and query processing and indexing. The conference is the premier annual event of the ACM Special Interest Group on Spatial Information (ACM SIGSPATIAL). Researchers, students, and practitioners are invited to submit their contributions to ACM SIGSPATIAL GIS 2013.