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One very effective way to make map information available to a group of nontechnical end users is to make it available through a web page. Web mapping sites are becoming increasingly popular. There are two broad kinds of web mapping applications: static and interactive. Static maps displayed as an image on a web page are quite common. If you already have a digital map (e.g., from scanning a document), you can be up and running very quickly with a static map on your web page. Basic web design skills are all you need for this because it is only a single image on a page.
Interactive maps aren't as commonly seen because they require specialized skills to keep such sites up and running (not to mention the potential costs of buying off-the-shelf software). The term interactive implies that the viewer can somehow interact with the map. This can mean selecting different map data layers to view or zooming into a particular part of the map that you are interested in. All this is done while interacting with the web page and a map image that is repeatedly updated. For example, MapQuest is an interactive web mapping program for finding street addresses and driving directions. You can see it in action at http://www.mapquest.com. Interactive maps that are accessed through web pages are referred to as web-based maps or simply web maps. These maps can be very powerful, but as mentioned, they can also be difficult to set up due to the technical skills required for maintaining a web server, a mapping server/program and management of the underlying map data. As you can see, these types of maps are fundamentally different from static maps because they are really a type of web-based program or application. Figure 1-2 shows a basic diagram of how an end user requests a map through a web mapping site and what happens behind the scenes. A user requests a map from the web server, and the server passes the request to the web mapping server, who then pulls together all the data. The map is passed all the way back to the end user's web browser. Figure 1-2. A diagram of how a mapping web site interacts with the end user and the back-end programs running on the servers1.3.1. Web Map UsersGenerally speaking, there are two types of people who use web maps: service providers and end users. For instance, I am a service provider because I have put together a web site that has an interactive mapping component you can see it at: http://spatialguru.com/maps/apps/global. One of the maps available to my end users shows the locations of several hurricanes. I'm safely tucked away between the Rocky and Coastal mountain ranges in western Canada, so I wouldn't consider myself a user of the hurricane portion of the site. It is simply a service for others who are interested. An end user might be someone who is curious about where the hurricanes are, or it may be a critical part of a person's business to know. For example, they may just wonder how close a hurricane is to a friend's house or they may need to get an idea of which clients were affected by a particular hurricane. This is a good example of how interactive mapping can be broadly applicable yet specifically useful. End-user needs can vary greatly. You might seek out a web mapping site that provides driving directions to a particular address. Someone else might want to see an aerial photo and topographic map for an upcoming hiking trip. Some end users have a web mapping site created to meet their specific needs, while others just look on the Internet for a site that has some capabilities they are interested in. Service providers can have completely different purposes in mind for providing a web map. A service provider might be interested in off-loading some of the repetitive tasks that come his way at the office. Implementing a web mapping site can be an excellent way of taking previously inaccessible data and making it more broadly available. If an organization isn't ready to introduce staff to more traditional GIS software (which can have a steep learning curve), having one technical expert maintain a web mapping site is a valuable service. Another reason a service provider might make a web mapping site available is to more broadly disseminate data without having to transfer the raw data to clients. A good example of this is my provincial government, the Province of British Columbia, Canada. They currently have some great aerial photography data and detailed base maps, but if you want the digital data, you have to negotiate a data exchange agreement or purchase the data from them. The other option is to use one of their web mapping sites. They have a site available that basically turns mapping into a self-serve, customizable resource; check it out at: http://maps.gov.bc.ca. 1.3.2. Web Sites with a Web Mapping ComponentThere are many web mapping sites available for you to use and explore. Table 1-1 lists a few that use software or apply similar principles to the software described in this book.
Figures 1-3, 1-4, and 1-5 show the web pages of three such sites. They show how diverse some MapServer applications can be, from street-level mapping to statewide overviews. Figure 1-3. The MapServer-based restaurant mapping application from MapItOutFigure 1-4. A MapServer-based tourism application for Hawaii from MapSherpaFigure 1-5. A web map for finding recreation sites in Minnesota, U.S.A.Of course, not all maps out there are built with MapServer; Table 1-2 lists other mapping sites that you may want to look to for inspiration.
1.3.2.1 Behind the web pageTo some people, web mapping sites may appear quite simple, while to others, they look like magic. The inner workings of a web mapping site can vary depending on the software used, but there are some common general concepts:
More information on the process of web mapping services can be found in Chapters 4, 11, and 12: those chapters discuss MapServer in depth. 1.3.2.2 Making your own web mapping siteThis book will teach about several of the components necessary to build your web mapping site, as well as general map data management. To give you an overview of the kinds of technology involved, here are some of the basic requirements of a web mapping site. Only the web mapping server and mapping data components from this list are discussed in this book.
Over the course of this book, you'll learn to assemble these components into your own interactive mapping service. |
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