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
Iowa 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:
http://cairo.gis.iastate.edu/search.html
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.
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…"