If you haven't been to A to Z Maps Online, then you've really missed a wonderful site, especially if you like maps. This site was already a very rich site, with a well organized mix of maps, made by the vendor and gathered from public sources. Now, the site has added over 70,000 new maps, by acquiring the entire 7.5 minute series of topographic quadrangle maps from the United States Geological Survey (USGS).
These maps cover every inch of every state in the U.S., and use contour lines to show elevation. A contour line is a line that connects points of equal elevation, and each map has a contour interval - the difference in elevation between one line and the lines on either side of it is known as the contour interval, and this interval is stated at the bottom center of each map. Take a look at a portion of the Evansville Quadrangle at the center left, that includes the Reitz Bowl, Reitz High School, and the surrounding Forest Hill area; places where the light brown contour line are closer together represent a steeper grade, and where they're further apart are gentler slopes.
So how do you find the topographic maps online? It's easy! Go the the Alphabetical Listing of Databases on the EVPL website, where A to Z Maps online is the very first choice, and then click on that link. You'll end up at a page that looks like the one to the left if you're at home. Just enter your library card barcode number into the appropriate box in the upper right hand corner, and click "Go!" Those boxes will then disappear, and instead you'll see the message "You are currently logged in!" in bright yellow type. (If you're in the library, that yellow type will show up immediately.)
Once you're there, find the "USGS Maps" tab on the green left hand menu, and click on it. A submenu will drop down, like the illustration bottom left. Look for the "USGS Topographic Maps of the US" link and click on that.
You'll be taken to a page that looks like the illustration in the center, below. On this page, clicking on the name of a state in the alphabetic list, or on the image of any state on the map, will take you to the index page for that particular state. A thumbnail of the index page for the state of Indiana is at the bottom right. There are three ways to find particular topographic maps, the first is to type in a word, like "Evansville" and that will present you with a list of all the Indiana maps that have "Evansville" in their name. The second way is to choose a quadrangle name from a complete drop-down list of names for the entire state, and the third way is to click on a letter of the alphabet, which will result in a list of every map that begins with that letter, along with a thumbnail view of each map.
In the results list, you'll often see what look like duplicate maps, except that the second map has the initials "TVA" in Parentheses following the name. These maps are Universal Transverse Mercator projections, very slightly different, at this scale, from the normal topographic projections.
I really enjoy looking at maps, and the USGS 7.5 series topographic maps have always been one of my favorites! It's great to have organized, online access to them in one place.
