Table of Contents for
Web Mapping Illustrated

Version ebook / Retour

Cover image for bash Cookbook, 2nd Edition Web Mapping Illustrated by Tyler Mitchell Published by O'Reilly Media, Inc., 2005
  1. Web Mapping Illustrated
  2. Cover
  3. Web Mapping Illustrated
  4. A Note Regarding Supplemental Files
  5. Foreword
  6. Preface
  7. Youthful Exploration
  8. The Tools in This Book
  9. What This Book Covers
  10. Organization of This Book
  11. Conventions Used in This Book
  12. Safari Enabled
  13. Comments and Questions
  14. Acknowledgments
  15. 1. Introduction to Digital Mapping
  16. 1.1. The Power of Digital Maps
  17. 1.2. The Difficulties of Making Maps
  18. 1.3. Different Kinds of Web Mapping
  19. 2. Digital Mapping Tasks and Tools
  20. 2.1. Common Mapping Tasks
  21. 2.2. Common Pitfalls, Deadends, and Irritations
  22. 2.3. Identifying the Types of Tasks for a Project
  23. 3. Converting and Viewing Maps
  24. 3.1. Raster and Vector
  25. 3.2. OpenEV
  26. 3.3. MapServer
  27. 3.4. Geospatial Data Abstraction Library (GDAL)
  28. 3.5. OGR Simple Features Library
  29. 3.6. PostGIS
  30. 3.7. Summary of Applications
  31. 4. Installing MapServer
  32. 4.1. How MapServer Applications Operate
  33. 4.2. Walkthrough of the Main Components
  34. 4.3. Installing MapServer
  35. 4.4. Getting Help
  36. 5. Acquiring Map Data
  37. 5.1. Appraising Your Data Needs
  38. 5.2. Acquiring the Data You Need
  39. 6. Analyzing Map Data
  40. 6.1. Downloading the Demonstration Data
  41. 6.2. Installing Data Management Tools: GDAL and FWTools
  42. 6.3. Examining Data Content
  43. 6.4. Summarizing Information Using Other Tools
  44. 7. Converting Map Data
  45. 7.1. Converting Map Data
  46. 7.2. Converting Vector Data
  47. 7.3. Converting Raster Data to Other Formats
  48. 8. Visualizing Mapping Data in a Desktop Program
  49. 8.1. Visualization and Mapping Programs
  50. 8.2. Using OpenEV
  51. 8.3. OpenEV Basics
  52. 9. Create and Edit Personal Map Data
  53. 9.1. Planning Your Map
  54. 9.2. Preprocessing Data Examples
  55. 10. Creating Static Maps
  56. 10.1. MapServer Utilities
  57. 10.2. Sample Uses of the Command-Line Utilities
  58. 10.3. Setting Output Image Formats
  59. 11. Publishing Interactive Maps on the Web
  60. 11.1. Preparing and Testing MapServer
  61. 11.2. Create a Custom Application for a Particular Area
  62. 11.3. Continuing Education
  63. 12. Accessing Maps Through Web Services
  64. 12.1. Web Services for Mapping
  65. 12.2. What Do Web Services for Mapping Do?
  66. 12.3. Using MapServer with Web Services
  67. 12.4. Reference Map Files
  68. 13. Managing a Spatial Database
  69. 13.1. Introducing PostGIS
  70. 13.2. What Is a Spatial Database?
  71. 13.3. Downloading PostGIS Install Packages and Binaries
  72. 13.4. Compiling from Source Code
  73. 13.5. Steps for Setting Up PostGIS
  74. 13.6. Creating a Spatial Database
  75. 13.7. Load Data into the Database
  76. 13.8. Spatial Data Queries
  77. 13.9. Accessing Spatial Data from PostGIS in Other Applications
  78. 14. Custom Programming with MapServer’s MapScript
  79. 14.1. Introducing MapScript
  80. 14.2. Getting MapScript
  81. 14.3. MapScript Objects
  82. 14.4. MapScript Examples
  83. 14.5. Other Resources
  84. 14.6. Parallel MapScript Translations
  85. A. A Brief Introduction to Map Projections
  86. A.1. The Third Spheroid from the Sun
  87. A.2. Using Map Projections with MapServer
  88. A.3. Map Projection Examples
  89. A.4. Using Projections with Other Applications
  90. A.5. References
  91. B. MapServer Reference Guide for Vector Data Access
  92. B.1. Vector Data
  93. B.2. Data Format Guide
  94.  
  95. ESRI Shapefiles (SHP)
  96.  
  97. PostGIS/PostgreSQL Database
  98.  
  99. MapInfo Files (TAB/MID/MIF)
  100.  
  101. Oracle Spatial Database
  102.  
  103. Web Feature Service (WFS)
  104.  
  105. Geography Markup Language Files (GML)
  106.  
  107. VirtualSpatialData (ODBC/OVF)
  108.  
  109. TIGER/Line Files
  110.  
  111. ESRI ArcInfo Coverage Files
  112.  
  113. ESRI ArcSDE Database (SDE)
  114.  
  115. Microstation Design Files (DGN)
  116.  
  117. IHO S-57 Files
  118.  
  119. Spatial Data Transfer Standard Files (SDTS)
  120.  
  121. Inline MapServer Features
  122.  
  123. National Transfer Format Files (NTF)
  124. About the Author
  125. Colophon
  126. Copyright

What Do Web Services for Mapping Do?

Mapping web services has been developed independently of the Web. They use similar approaches and follow some common communication protocols, but the web services for mapping are maintained independent of web services in general.

Web services for mapping are the future of web mapping. Computing and network resources have reached the level of sophistication to make this possible. As data sources continue to expand, the demand to have access to them increases. Meeting this demand will only be possible using mapping web services.

Web services for mapping essentially fill two roles: accessing remote data sources as a consumer and serving up or sharing data as a provider for others. Web services for mapping are all about sharing information.

Accessing remote data sources requires some specific knowledge about the data source. Particulars may include the server address to connect to, the data layers available, or the format the data can be sent to you in. Once you know the details, you can set up your application to request exactly what you want. MapServer will add in its own pieces of information to each request so you get something logical back on a map.

Sharing (a.k.a. publishing) your own data is relatively easy to do. A few additions to your application will allow others to query it for such things as available layers and data format options. Once you’ve made a few modifications to your map file, other users can add your layers to their applications.

Web services for mapping don’t require you to know a bunch of details about how requests are made or sent. MapServer will take care of the guts of the operation for you, such as sending HTTP or XML-based requests and receiving responses and data. You usually won’t have to read XML when using these services. However, you might occasionally need to review an XML-based document to learn more about a service.

Tip

The examples in this chapter walk you through the steps of building your own request manually. You can then incorporate this technology into your own applications. If you are just planning to have MapServer broker requests to a WMS server, then you won’t need to pay as much attention to the manual examples.

Just as telephones or CD players use common methods for sending or receiving information, so do mapping web services. Therefore, other products or applications can work together as long as they use the common standards or protocols.

Why Use These Services?

There are various reasons for sharing and accessing map data using web services. A government or large corporation may make map data available so that other divisions or departments don’t need to store their data locally. Consider the cost savings often touted for centralizing data storage. If data is centralized, the users still need to access it. Web services for mapping make the data available.

Perhaps someone is willing to share data with you but can’t allow you to have a complete copy, for whatever reason. A web service can facilitate that. Some map data, such as hurricane locations, is constantly changing. Downloading that data might not be possible or timely. Integrating a layer in your map that accesses a web service in realtime might be the answer. Some data repositories are so large that it would be unrealistic to copy them to your location. Web services can make that data available for you at the time you need it. This helps reduce the need for continual data storage upgrades. Figure 12-1 illustrates the basic function of a MapServer application accessing remote data through a web services request.

Whether sharing or accessing, it is all about making the most of our time and resources. Continually changing an application to point to new data can be inefficient. Storing large amounts of data locally may also be an unreasonable option.

Internal Versus External Needs

Some service providers sharing data will never use the information internally. For example, think of a government agency that makes mapping data available to the public. The public benefits by having free and open access to mapping information. The government benefits by successfully fulfilling their mandate. Providing web services for mapping data can require a serious commitment to openness and support for clients.

On the other end of the spectrum, a company might share data internally and never share it with the public. Web services don’t require that the data be publicly accessible. Services can be securely guarded like any other web page or internal application. Large corporations may use services internally to make data broadly accessible

MapServer requesting map data from a remote web server
Figure 12-1. MapServer requesting map data from a remote web server

without having to maintain redundant hardware infrastructures across divisions. This can be a cost-reduction measure, but it can also improve service to users. Users need two things: access to information and access to information in the right format. The benefit of mapping services is that a data source can be made available, and how the data sources are formatted or presented can be managed as well.

Both internal and external needs scenarios can be handled equally well through web services for mapping with MapServer.