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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Quantifying the social and economic value that geospatial information contributes to modern society is a complex task. To construct reliable and consistent valuation measures requires an understanding of the sequence of processes that starts with data acquisition, and leads to decision-makers’ choices that impact society. GEOValue explores each step in this complex value chain from the viewpoint of domain experts spanning disciplines that range from the technical side of data acquisition and management to the social sciences that provide the framework to assess the benefit to society. The book is intended to provide foundational understanding of the techniques and complexities of each step in the process. As such it is intended to be assessable to a reader without prior training in data acquisition systems, information systems, or valuation methods. In addition, a number of case studies are provided that demonstrate the use of geospatial information as a critical input for evaluation of policy pertaining to a wide range of application areas, such as agricultural and environmental policy, natural catastrophes, e-government and transportation systems.

The report discusses issues that may be of interest to Congress-managing, sharing, and coordinating geospatial information-and includes examples of legislation. The report also summarizes a diverse set of recommendations and proposals from different non-governmental organizations for how to improve the coordination and management of geospatial information at the federal and state levels.

With the turn of the century our ability to collect and store geospatial information has increased considerably. This has resulted in ever-increasing amounts of heterogeneous geospatial data, an issue that poses new challenges and opportunities. As these rich sources of data are made available, users rely, now more than ever, on the geospatial data