Do-It-Yourself GIS, Episode One

So you want to start playing around with GIS (Geographic Information Systems) on your home PC? Here’s a simple guide on how you can start exploring maps of Prince Edward Island using only free data and free tools.

First, go and grab a copy of ArcExplorer from ESRI. This is a free basic GIS tool that will allow you to load digital map files, and do some basic queries. ArcExplorer is available for Windows, Mac, and Linux; pay attention to the “Supported Platforms” section of the download page to make sure you get the right version. Download the version you need, and follow the instructions for installing it.

Next, go to the Geobase download page for the National Road Network and download the “ESRI Shapefile” format of the file for Prince Edward Island. This is a 2MB ZIP file. Unzip the file once it has downloaded (on a Mac you can simply double-click on it; on the PC you may need a tool like WinZIP). The result will be 31 files with extensions like “shp” and “dbf.” Remember where these files ended up.

Now you’re ready to play.

Start up ArcExplorer; you’ll see a blank map screen (your ArcExplorer might not look exactly the same as below; I’m using the “Java Edition for Education” on the Mac):

Click on the Add Data icon on the toolbar (it’s the one with the yellow “plus sign” on it):

Locate the directory where you saved your GeoBase National Road Network, highlight the file named ROADSEG.SHP, and click OK.

The roads of Prince Edward Island will load into the map window. Depending on the speed of your computer, and the version of ArcExplorer you’re using, this might happen instantly, or could take a minute or two. In any case, the result will look like this:

What you’re looking at are all the roads of Prince Edward Island. You’ll notice that the ArcExplorer toolbar now allows you to select a host of additional icons. For example, click the “Zoom In” icon (it’s a magnifying glass with a “plus sign” on it):

Next use your mouse to draw a box around an area of the map, the map will “zoom in” to that area. Here’s the map of Prince Edward Island’s roads “zoomed in” to Charlottetown.

You can also “zoom out” (the magnifying glass with the “minus sign”), and pan (the hand icon; lets you drag the map to see a different area).

In the next episode, we’ll look at some of the other tools, and we’ll grab some other layers for the map.