Items by Adams, Christopher

Street maps are a key element to Local Search; they make the connection between the search results, and the geography. Adding a map to your website can be easily done, using an API from a popular local search provider. However, the lists of restrictions are lengthy and customization can be costly, or impossible. It is possible to create a fully customizable web-deployed street map without sponsoring the corporate leviathans, at only the cost of your time and your server. Being able to freely style and customize your map is essential; it will distinguish your website from websites with shrink wrapped maps that everyone has seen. Using open source software adds to the level of customizability - you will not have to wait two years for the next release and then maybe get the anticipated new feature or the bug fix; you can make the change yourself. Using free data rids you of contracts, costly transactions, and hefty startup fees. As an example, we walk through creating a street map for the United States of America. A Web-deployed street map consists of a server and a client. The server stores the map data including any custom refinements. The client requests a portion of the map and the server renders that portion and returns it to the client, which in turn displays it to the user. The map data used in this example is the Tiger/LINE data. Tiger/LINE data covers the whole of the USA. Another source of free road network data is OpenStreetMap, which is not as complete as Tiger/LINE but includes additional data such as points of interest and streets for other countries. Sometimes the original data is not formatted in a manner that attributes to a good looking, concise map. In such cases, data refinement is desired. For instance, performance and aesthetics of a map can be improved by transforming the street center lines to street polygons. For this task, we use the Python language, which has many extensions that make map data refinement easy. The rendering application employed is MapServer. MapServer allows you to specify a configuration file for your map, which consists of layers referencing geographical information, as well as the style attributes to specify how the layers are visualized. MapServer contains utilities to speed up the rendering process, and organize similar data. On the front end, we need a web-page embeddable client that can process requests for map movements, and scale changes in real time. In our experience, OpenLayers is this best tool for this task; it supports many existing protocols for requesting map tiles and is fast, customizable, and user friendly. Thus, deploying a street map service on the Web is feasible for individuals and not limited to big corporations.