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Book Review: Web Mapping Illustrated by Tyler Mitchell

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First piece of advice: if you’re like me, a tech-savvy civilian, but by no means a programmer, don’t assume you can buy this book and jump right into creating cool maps&#8212especially if you don’t have a better-than-passing familiarity with DOS. The programmer-author understandably makes a few assumptions about what you’ll know about simple things like changing directories and so on within DOS.

After installing the data management tools (FWTools) and downloading the example data, it became clear to me that there was a lot about DOS I didn’t know. Luckily, in one of the chapters author Tyler Mitchell mentions a Listserv group you can join, which I did. And when I emailed the group to ask why I wasn’t able to get the same data to appear with that DOS instruction, who should reply but the author himself! How’s that for technical support?

Anyway, moving further into this early chapter, I learned that it would be nice if I knew about SQL and if I didn’t, I could look this up in another book. Well, at least he’s not writing for SQL programmers, I thought, and decided I’d skip that part. Still I began to fear that I’d gotten in hopelessly over my head.

But I plunged on to the instructions for installing the recommended mapping software OpenEV. Turns out it had already downloaded with the FWTools, and all I had to do was click the desktop icon. First a blank DOS window opened&#8212the book instructs you immediately that you should leave this open because OpenEV needs it to run. And simultaneously several other screens pop open. And the book reassures you that yes, these windows should be open. Okay, so far, so good.

By the way, Mitchell gives alternate instructions throughout the book for both Windows users and Linux users&#8212written simply and clearly. Lots of subheadings in each chapter help you compartmentalize the information in your head as you learn-and-do. I was regaining confidence that I could do this.

Now it was time to add the example data into the OpenEV program. Happily the author notes that Windows users might get confused by the way the files are listed&#8212how did he know?!&#8212and would need to navigate down to the proper drive. Voila! A blue screen appears with little stars showing where the airports are located in the demo data. And then you’re directed to the Layers screen, which indicates the full path to the layer you’ve got open—and has a big eye graphic next to it that works just like the Photoshop eye. Click and the layer disappears in the view screen; click again and it reappears.

Now I’m learning about layer properties. Seems the OpenEV is pretty special among free mapping programs in that it lets you edit vector data files&#8212meaning you can move features around, create new ones, delete them, or reshape lines. He suggests changing this setting to “No,” so you don’t accidentally modify features&#8212a good move for overenthusiastic types like me. Next he takes you through the drawing options&#8212and look, now the layer shows the names of the airports. Once you add another layer by selecting the .SHP file for the road data from the demo dataset&#8212behold, you have created a very simple map.

Now you get to make it clearer by playing with the drawing styles to change line colors, points, and changing the order of layers, etc. Changes appear on the fly. Cautions about appearance and clarity are similar to those in any page layout program such as Adobe InDesign, or even in Word if you happen to be forced to try to construct layered items in that finicky program.

Now you learn about some basic visualizing tools (many of which are designed for raster data, but work with vector data as well). You’ll learn simple techniques to zoom in on selected areas of your map, pan (slide the map to see different areas instead of zoom&#8212a cool feature in the new Google Maps), and use color theming to classify specific subdata within a layer (say, different types of roads within the roads layer).

Next, you learn to load a raster layer&#8212a single-file image layer in a graphical format like .tif&#8212and re-project it so that it matches another layer. In this case, you must transform the coordinates of the airport data from one spatial reference system to another. And here we move back into DOS, where the process gets less intuitive again.

Additional chapters take you through mapping a fire-ravaged area in Canada, showing you how to clip out areas on your maps, how to use operators to create filtered versions, and how to create a map legend, add a scale bar and set the image output. It covers interactive maps on the web, and talks about using MapServer on Linux with Apache. There’s even a little explanation of XML.

Of particular interest was the part on using Web Services (WMS) to make your map data available to others in a simple image format&#8212and to get map data from elsewhere. After all, what good are beautiful maps if you can’t show them to other people, eh? The diagram illustrating how the data flows to give a user a requested map image makes the process look simple and clear.

I decided to download the Open Geospatial Consortium (OGC)Web Services Workshop package (I love all this open-source free software!), but that’s where I had to stop. This is a well-written book&#8212clear, concise, with lots of tips and. A non-programmer like me could get so far as to create a real map&#8212though granted, he gets you started with a nice fat file of complex sample data that you’d have to create yourself if you were doing your own maps. This is a book that will let even a non-expert play at the magical art of mapping.
ed/Pub:NB Edited: PC

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