Tile-Based Geospatial Information Systems

Tile-based mapping systems have grown to become the dominant form of mapping system with the rise of Web-based mapping tools. The origin of this book is a desire to collect all our discoveries, techniques, and best practices for creating a til- mapping system into one combined volume. The intent of this text is to provide a comprehensive guide to the theory behind creating a tiled-map system as well as a practical guide to create a concrete implementation. Stennis Space Center, MS John Sample May 2010 Elias Ioup vii Acknowledgements The authors would like to thank the Naval Research Laboratory’s Base Program, program element number 0602435N, for sponsoring this research. Additionally, the following people provided technical assistance without which this book would not have been possible: Perry Beason, Frank McCreedy, Norm Schoenhardt, Brett Hode, Bruce Lin, Annie Holladay, Juliette Ioup, and Hillary Mesick. ix Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. 1 Background of Web-Based Mapping Applications . . . . . . . . . . . . . . . 1 1. 2 Properties of tile-based mapping systems . . . . . . . . . . . . . . . . . . . . . . . 2 1. 3 Book Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 Logical Tile Schemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. 2 Global Logical Tile Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2. 3 Blue Marble Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2. 4 Mercator-Based Schema . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2. 5 Variable Start Tile Schemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2. 6 Standardized Schema . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3 Tiled Mapping Clients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3. 1 Tile Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3. 1. 1 Discrete Map Scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3. 1. 2 Continuous Map Scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3. 2 Tile Retrieval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3. 2. 1 Local Tile Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Dr. John T. Sample has worked for 12 years as a scientist in the Naval Research Laboratory’s Geospatial Sciences and Technology branch. He has authored and edited articles, books, and book chapters on the topic of web based GIS. He currently has two patents granted related to web based GIS. He has developed a number of tile-based mapping systems in use by the Department of Defense and Department of Homeland Security. Dr. Sample received a Ph.D. in computer science from Louisiana State University in 2003 and a B.S. in mathematics from the University of Southern Mississippi in 1999.

Elias Z. K. Ioup is a Computer Scientist with the Naval Research Laboratory working on several geospatial research programs. He is the principal investigator for the GHUB Distributed Geospatial Repository program and a lead developer on the Geospatial Information Database (GIDB). These programs represent leading DoD efforts to leverage geospatial capabilities using Service Oriented Architectures and Web services. Elias Ioup received a Master’s degree in Computer Science from the University of New Orleans in 2006 and Bachelor's degrees in Mathematics and Computer Science from the University of Chicago in 2003. He is currently a Ph.D. candidate in Engineering and Applied Science at the University of New Orleans.