Using the Geographic Map Server

a how-to guide

Using Iowa State University's Online Iowa Geographic Map Server

A Birder's Resource for Aerial Photographs and Topographic Maps Showing Every Inch of the Hawkeye State

by Mike Dooley

GIS Map of Montrose, Lee CountyIowa State University has a website that is part of their Geographic Information Systems from which you can pull up aerial photographs and topographic maps of any township section in the state of Iowa. You can zoom in on any location in the state to such a magnification that one pixel of the image is equal to a mere one square meter of surface. I discovered this resource while compiling the Rare Bird Alert, and used it to find boat ramps, access roads, parking areas, obscure ponds within wildlife areas or along country roads, dike walks within marsh areas, trails, creeks, small rural cemeteries, exact configurations of back roads, Mississippi River viewing spots, and any number of other geographic tidbits useful to birders. Here I present basic directions for using this excellent resource, mainly in conjunction with the Iowa Sportsman's Atlas, and take the reader through two examples: (1) Frytown Conservation Area in Johnson Co., a fairly garden-variety DNR wildlife area, chosen because it makes for an easy beginning; and (2) Pinchey Bottoms in Marion Co., which gives a taste for the sorts of discoveries you can make about an area when using the map server. At the end of the article is a brief word on searching by town and on downloading your images.

Begin at the following URL:

This brings you to the Map Search page. There are three main menus here, and we'll begin with the topmost, "Select a township, range and section number." There are three simple drop-down menus here which are labeled, from left to right, "Township," "Range," and "Section." Township numbers are found just outside the left and right edges of the county maps in the Sportsman's Atlas, and begin with the letter T. Range numbers are at the top and bottom edges of the maps, and begin with the letter R. Every Iowa township has a unique combination of township and range number. For example, turn to the Johnson County map on page 66 in the atlas and find Washington Township in the southwest corner of the county. The corresponding township number is T-78N, and the range number is R-8W. Directly northeast of Iowa City find Graham Township. Graham's numbers are R-5W and T-80N.

As is true throughout the midwest, each Iowa township is divided into 36 sections, and each section is one mile square. Further, each section is assigned a number from 1 to 36. The numbered sections in a given township are ordered in an unexpected fashion. Section 1 is in the northeast corner of the township; from there the numbers move left to right, to the northwest corner. In the next row down, however, the order continues right to left (west to east). The remaining rows continue this zigzag pattern.

Frytown Conservation Area. Find Frytown Conservation Area in southwestern Johnson Co. and note that it is located in Section 1 of Washington Twp. (And note the order of the 36 numbered sections in the county). To pull up either an aerial photograph or a topographical map of Frytown, choose the following parameters from the drop-down menus: Township T-78N, Range R-8W, Section 1. Now click on "Show Map." By default, an aerial photo comes up (as opposed to a topo map), showing the entirety of Section 1 and a little bit extra besides. Also by default, an overlay is superimposed on the photo showing and naming the roads and highways as well as the township and range numbers. If you desire, this overlay can be removed. Just above the upper right corner of the photo is an option called "Remove Overlays." If you click this, the image refreshes without the superimposed labels. The labels are removed from all succeeding images you pull up as well, until you restore that option.

To the left of the photo you've brought up is a menu entitled "Select a map layer." Usually the "natural color" and "gray-scale" options, all at the top of the menu, are your most useful aerial photo choices, although the "color-infrared" has its uses as well. A green star marks which particular map layer type you are currently looking at. By clicking on the little circles, you can choose whatever image type you prefer, including topographical maps. You will then need to go to the bottom left corner of the webpage and click the "Refresh Map" bar.

Returning now to Frytown Conservation, choose "2004 USDA Orthophotos (natural color)" and refresh the image ("Refresh Map"). If you look down in the southeast section of the photo, the entrance to Frytown is where diagonally-running Angle Rd. meets the sharp southward bend of Hwy. 1. You can already see the early part of the main trail, visible because it goes through a shrubby section as opposed to woods, winding off westward from the entrance. West of the trail the dark textured areas are, of course, woods. Let's zero in on that first section of the trail. Above the "Select a map layer" menu to the left of the image is a menu called "Click on the map to." By default, "Recenter" is selected. Put your mouse arrow's point on a spot in the middle of that whitish line of trail and click. The image refreshes and now the spot that you clicked is in the exact center of the photo.

Now let's zoom in. You can do this in one of two ways. Under the "Click on the map to" menu, select "Zoom IN," and simply click on the spot you want to zoom in on. Or, there is a third menu, below "Select a map layer," called "Select a zoom level." The zoom levels here are calculated in meters per pixel. In other words, at the default level of "5m pixels" each pixel in the image shows a five-meter-by-five-meter section of land. You can choose a zoom level and then click "Refresh Map." The image will zoom in or zoom out while staying centered where you last left it. A red star indicates which zoom level you are currently at. Therefore either click once on Frytown's trail to zoom in or choose "2m pixels" and refresh the map.

At this level you can see how the trail turns northward, emerging from a thin section of the woods, and eventually turns westward again. The lighter tract of land, between the north and south layers of woods, is shrubby habitat.

The natural color orthophotos will only magnify to a level of 2m pixels, whereas both gray-scale choices and the color-infrared will magnify all the way to a level of 1m (one square meter per pixel). So, if we click one more time to zoom in on Frytown's trail under the color photo option, we will be stopped at the second-to-highest magnification; the final image (at 1m pixel) fails to appear and there is a message at the top of the photo frame telling us that we can't magnify that high.

Therefore switch over to a "2002 IGIC-IDNR Orthophotos (gray-scale)" image by selecting its circle and refreshing the map. (Sometimes the 1990s gray-scale photos are better than the 2002 versions for a given spot, so try both if you need to). Then choose the "1m pixels" level at the bottom of the "Select a zoom level" menu, and refresh the map again. Now you have your maximum close-up view of the first part of Frytown's main trail. Not the most exciting image, but if you know the park a little, you can recognize the more open shrubby habitat along either side of the trail, and the thicker woodlots farther to the edges of the property. We used Frytown as an example because it's easy to read its location numbers in the atlas. When you're dealing with big red natural areas, especially those that include bodies of water like Coralville Reservoir or Lake Rathbun, it can be trickier trying to find the section number you want.

A couple of times when first wandering Frytown I found myself walking alongside a pond in the woods, on a lesser trail beyond the footbridge where the main trail ends. I was never sure exactly how I got there, so let's try to locate it using the map server. Zoom the current image back out to the 5m pixels level by choosing that level and refreshing the map. Now we have a general view of the park again. I know this pond was at the west end of the park. Therefore select "Zoom IN" on the upper menu and then click in the middle of that dark, vertical rectangle of woods to the left. Look around the woods a little and you should spot the small pond before long, in the southwest corner. Being a body of water, it will show up particularly well in an infrared photo. Under "Select a map layer," choose the infrared option and refresh the map. Both the pond and the two creeks, one larger than the other, show up darker than the surrounding habitat.

On the right side of the image you can see the open shrubby section of the park. You can also see the main trail enter the woods at the northwest corner of that shrubby section. The trail seems to eventually turn southward and reach the smaller creek. If you've walked Frytown before, you know that this must be where the footbridge is. The way to the pond isn't apparent at this level, however. So, zoom in on a spot betweent the bridge and the pond. Make sure you've selected "Zoom IN." I had mentioned earlier that this was a lesser trail. At this new magnification, it indeed looks like there are segments of a trail visible here and there. Some kind of trail-like line passes along the north side of the pond, for example, and then sweeps up toward the creek again. I do remember that at one point I was following alongside that creek back to the footbridge.

Perhaps a regular photo will show the trail better. We're already at the maximum 1m pixel level, so it will have to be one of the gray-scale options. Choosing the 2002 gray-scale image, it does look like there's a trail starting at the footbridge that curves toward the pond, although we still can't pick it out in its entirety.

GIS Map of Pinchey Bottoms, Marion County Pinchey Bottoms. Let's try another example, the so-called "Pinchey Bottoms" shorebird area in Red Rock W.A., not shown in the Sportsman's Atlas or on any other map. On the topmost menu bar above your current image of Frytown, click "Map Search." This returns you to the township/range/section menu. Directions on the I.O.U. website's gazetteer tell us that Pinchey Bottoms is in the northwest corner of Marion Co. (page 76 in the atlas). We're told there's an access road heading north to the area from where Dubuque St. bends southward becoming 40th St., but this access road isn't shown on the atlas map. According to the above information, Pinchey Bottoms appears to fall within the parameters of Township T-77N and Range R-21W. On close inspection, that northbound access road would seem to fall on the border between Sections 21 and 22. Let's pick 21 to start. Once the image of Section 21 comes up, at the default 5m pixels level, choose the color photo option and refresh the image. The area of the famously productive mudflats and shallows is immediately obvious in the upper right corner of the photo. Equally obvious is the access road that ends at Pinchey Bottoms. You can also see that this old roadbed continued farther north at one time; remnants of it are visible in the photograph. If you've birded Pinchey Bottoms, you know that these are the sections of the walk out there that are sometimes slightly under water, sometimes above.

To get a better general view of the flats, click in the middle of the main brown patch, and by default the image will re-center on that spot. Next zoom in on where the access road first meets the mudflats. Do this by choosing "Zoom IN" from the "Click on map to" menu at top left and clicking on the end of the road. Now you can really see how the old roadbed disappears under water, which is why rubber boots are a must for walking the trail north. You can also see the parking spot on the left side of the road. If you want to see Pinchey Bottoms in context of the general area, switch to the 2002 color-infrared option, and then zoom out to a level of "10m pixels" by using the "Select a zoom level" menu. You'll have to click "Refresh Map" both times. Bodies of water appear dark in infrared photography, and the deeper the water, the darker it shows. You can see from the image you've just pulled up that Pinchey Bottoms is shallow compared to the Des Moines River to the north. On the other hand, you can also see that there is a small body of water to the northwest of the main flats that is deeper than the rest of the area—a good marsh, perhaps. The old roadbed seems to reach to just past that water.

In fact, try switching the present view over to "Topo Maps 1:24,000-scale" from the "Select a map layer" menu. Now we can see, from the topographical map, that at one time this road crossed all the way over the area, meeting another road just south of the river. That small, deeper body of water we noted also shows up on this map, in blue. With "Zoom IN" selected, try zooming in on that water by clicking it once, waiting for the new image, and then clicking on it again, bringing the map to 2m pixels magnification. It turns out that it's an old gravel pit, labeled as such, and obviously now abandoned. The remnant of its entrance road, shown as dashed lines, must be out there in the area somewhere. If you back up to the 5m pixels level and get re-centered on the parking area for Pinchey Bottoms, still using the topo map image, you'll learn that it is Sugar Creek that feeds the area. At 2m pixels, you'll see an old lane, marked in dashed lines, going off east from the parking spot, along the shore of the shallows. Maybe this is a way to get another view on Pinchey Bottoms.

Search by City. As a last bit of introduction to the map server, you might also go back to the original page and work with the second option, "Select a City." There you will find a drop-down menu listing all Iowa cities in alphabetical order, which works the same as for townships, ranges, and sections. This is useful, for example, in exploring the Pool 19 scoping spots around Montrose in Lee Co. In fact, you can use the arrow navigation icons surrounding the photos or topo maps to "cross" the Mississippi River from Montrose and explore Nauvoo, Illinois as well.

Download Images. All the images you pull up are downloadable. In the upper left portion of the image page, under the GISU logo, click on the link "Download map." You'll be given a list of choices regarding file type, file size, magnification value, and optional informational headers. After you click on your choice, eventually another page is brought up that is blank except for the image. From there you can save the image to the folder of your choice. If you have a PC, for example, right-click on the image and choose "Save Picture As…"