TileBased Geospatial Information Systems: Principles and Practices,Used

Tilebased mapping systems have grown to become the dominant form of mapping system with the rise of Webbased 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 tiledmap 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 Laboratorys 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 WebBased Mapping Applications . . . . . . . . . . . . . . . 1 1. 2 Properties of tilebased 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 MercatorBased 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .