Developing geographic applications is far more complicated than itshould be. I have several goals for this book. The first is to demystifygeographic information systems (GIS) and teach you a bit of the lingo.The second goal is to help you download some free data and learn aprogrammatic API or two. These lead to the final goal of turning youinto a GIS developer.Demystifying GISMany popular websites have GIS underpinnings (and you don’t need aPhD to use them). MapQuest1 is perhaps one of the most well known.In the late 1990s, it virtually owned the online mapping market.In the following years, additional players joined the game. All the majorsearch engines now have GIS offerings. For example, take a look atGoogle Maps.2 You simply enter a street address, and it shows you thelocation on a map. Yahoo3 and MSN4 offer similar functionality.Although all these sites provide a valuable service, they do little to raisethe geographic literacy of the general public. I can’t criticize them toomuch for this—I’m sure that ease of use was their primary design goal.But by shielding us from the complexity of the GIS problems they solve,they don’t help us build GIS solutions of our own. They are “blackboxes” of geographical wonder.Similarly, most consumer-grade global positioning system (GPS) devicesare sold as black boxes as well. In-dash GPS is fast becoming the derigueur option in high-end automobiles, but most drivers would nomore consider customizing them than they would try to change thesound of their horn or the wiring of their radio.I am not suggesting that everyone who drives a car should be a mechanic,or even want to be. But for those of us who are just the slightestbit curious, it would be nice to be able to crack open the hood and pokearound. Maybe I’ve just been spoiled by my years as a web developer.When I come across a cool website, I can not only appreciate it as anend user but also choose View > Source to see how it was put together.To me, this is the best of all worlds—let it be a black box to those whodon’t care to look any further, but also cater to those who want to liftup the corner and nose around the insides a bit. I firmly believe thatthis democratic approach to the technology is one of the primary forcesbehind the Web’s rapid growth and widespread adoption.Unfortunately, this do-it-yourself, learn-from-others gestalt is missingfrom the GIS examples we’ve discussed so far. The fact that there isn’t ababy step up to the next level of difficulty only compounds the problem.There seems to be very little middle ground when it comes to complexityin GIS applications. Compared to MapQuest, programs that exposetheir GIS underpinnings are a giant leap up in terms of complexity. Thegood news is even with just a little bit of industry knowledge, you canput together some impressive results with the free tools and data outthere.So, regarding my first goal for the book, the “blithely ignorant end user”segment and the “all-knowing industry veteran” segment are both well

represented in the GIS space. My hope is that this book will allow you tojoin the small but growing middle class of GIS users—those who “knowmore than some but not as much as others.” (The cool kids are callingthese folks neogeographers.)Finding Free Data Sources and ApplicationsWith only a little bit of vernacular, you can access significantly more“white-box” GIS resources. The trick is finding them. The second goalof the book is to show you where they are and how to assemble theminto a meaningful application.You should be reasonably comfortable downloading and configuringpopular open source programs. Java developers pull down Ant, JUnit,and the JDK all the time. Rubyists install MySQL and Rails regularly.These are not niche applications; they are core to the development process.The GIS domain is no different. A number of free and open source applicationsare crucial to your success as a GIS developer. In fact, someopen source desktop GIS applications rival the capabilities of their commercialcounterparts. There are standards-based web frameworks thatallow you to display GIS data in a browser. There are GIS databases andcommand-line utilities—all free and released under the usual assortmentof open source licenses.The one area that might seem a bit more foreign to nonmapping programmersis the quest for downloadable free GIS data. Unlike traditionalprograms where the majority of the data is generated by theapplication itself, most GIS applications need to be seeded with somepreexisting data.For example, consider a GPS application. As you hike up a path ordrive along a road, your GPS unit can be configured to periodically dropdigital bread crumbs called waypoints. This allows you to see whereyou’ve been and backtrack along the same path if necessary. Althoughthe waypoints are a major part of the application, they are only part ofthe picture (literally!). If the screen simply shows a series of black dotsfloating on a white background, it doesn’t do you much good. In otherwords, showing only the generated data isn’t enough. Showing thosepoints in relation to a basemap (a map showing the roads or hikingtrails in the area) is where the real value comes into play.There is a vast amount of free basemap data on the Web. The problem isit isn’t gathered together in one place, and the popular search enginesdon’t have targeted searches for geographic data like they do for we
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ages, images, music files, and so forth. Finding the right basemapdata for your application is often more of a challenge than using it onceyou have it.Sometimes simply combining existing map data in a unique and meaningfulway is all you need to do. For example, you might choose todisplay all cities in the United States over a basemap of state boundaries.This data is available and requires no further manipulation. Yourjob is to bring it together and display it.Other times the data your application generates needs to appear inthe context of a known set of data. You might decide to display citieswith populations over a certain number and then overlay that data withsales regions where profit margins exceed a certain percentage. Thecombinations of generated data and basemap data are endless, andthe tools to help you display and manipulate them are out there justwaiting to be used.So, as I mentioned, the second goal of this book is to give you a guidedtour of the Internet, showing you where all the best nooks and cranniesare for finding free GIS applications and data sets. (Check out the companionsite for this book—http://www.mapmap.org—for up-to-date linksto all the data and applications mentioned here.)