Here are just a few examples of issues that can be addressed with the GIS resources available on campus: determining where new parks are needed in Northfield; measuring a jogging route through the Arb; monitoring watersheds of the Cannon River; identifying areas in Northfield that could be targeted for large new retail stores; planning a project at a biological research station in Costa Rica; finding out where porn shops are allowed in Northfield.
But what is GIS, anyway? A Geographic Information System (GIS) is essentially a collection of digital maps that can be stacked, viewed, and – most importantly – used for spatial analysis.
Essentially any kind of map can be put into and used in a GIS. Our GIS of Northfield includes maps of roads, parks, land use, soils, bedrock geology, bedrock topography, watershed divides, bodies of water, schools, storm sewers, and even campus tunnels. We also have digital elevation models, digital orthophoto quadrangles (black and white aerial photos with one meter resolution), digital raster graphic (scanned in USGS topographic maps), and Landsat images of this region.
Many of the maps contain supplemental information in table form. For example, a map of the trails in the Arb has an associated table that contains information for trail segments, including length, whether or not bikes are allowed, and whether the trail is maintained or not.
The spatial and tabular data, plus a little computing power, work together to produce the real strength of GIS which lies in its ability to do spatial analysis. With the appropriate maps, a GIS can be used to calculate the area in use as farmland, to find the length of streams, to highlight streets with a certain name, to generate a map which represents the distance to the nearest park, to determine slope from a digital elevation model, or to delineate watersheds. Any one of these tasks would be slow and tedious with standard paper maps, but can be executed with ease using a GIS. By asking the GIS a combination of questions and performing queries, a wide variety of real world questions can be answered.
Several such questions regarding local issues were studied through GIS projects by students in last term's Remote Sensing and GIS class taught by Mary Savina of the Geology Department. Seniors Kim Hanson and Ann Isaksen assessed the issue of park siting in Northfield. In addition to considering the adequacy of the current park distribution, they contemplated the question of where new parks should be located.
The map on the right shows one of the first steps in their process: determining how far any given location in Northfield is from the nearest park. According to national recommendations for parks, no residence should be greater than a quarter mile (about 400 meters) from the nearest park. As can be seen in the figure, there are two isolated areas within Northfield that do not meet this recommendation, and both of these fall primarily in residential areas which are not realistic locations for new parks. However, the areas on the outskirts of town, where new developments will go, are the prime areas in need of attention for future parks planning.
The Public Park section of the Northfield Subdivision Ordinance ensures that a certain amount of park land will be set aside for each new development; however, there are no specifications about the shape of the parks. Ann and Kim's analysis involved quantifying the edge to area ratio of the parks, which they associated to some degree with the desirability of the parks, for the following reason: "many of the newest parks are more like buffer zones than parks--long, skinny tracts of land that appear to have been built more to comply with the ordinance and provide a semblance of privacy to new residences than to serve as functional parks."
To avoid having parks that are little more than extended back yards, they suggested taking the edge to area ratio into account for future park planning. Fortunately, with GIS, this is easy to do.
Another example of a real world issues addressed by GIS students was an analysis of the Northfield Adult Use Ordinance, which restricts adult use establishments (such as porn shops) to the industrial district and requires a buffer zone of 400 feet around schools, day care centers, religious institutions, and so forth. Such specifications provide just the type of problem that a GIS is good at answering, and so this became a project in the class.
The ordinance was enacted because of high crime rate in other cities associated with the siting of such adult use establishments. The ordinance was not intended to completely exclude adult use establishments, but whether or not this was the case was not immediately clear. The results of the GIS analysis showed that there were some areas in which adult use establishments would be allowed. Ambiguities in the wording of the ordinance also surfaced during the work. For example, it is unclear whether Carleton counts as a school.
In using a GIS system, the analysis often is the easy part. The data acquisition and input often prove to be difficult and time consuming, as the map layers often must be transformed into the standard datum and projection with appropriate documentation (metadata). The data sources are varied. Maps that are already in digital form come from sources such as the U.S. Geological Survey and the Minnesota DNR. Paper maps- from the city of Northfield, for example- can be entered into the computer by manually digitizing them. Finally, students can create their own maps using Global Positioning System (GPS) receivers.
The GIS data that are now available on campus have been compiled with much success through the hard work of students, faculty, and staff faculty during the last few years. As a result, we now have GIS's (that run on ArcView software in the Geology labs) for several local watersheds, Northfield, the Arb, McKnight prairie, the Carleton campus, and La Selva Biological Research Station in Costa Rica. The development of these GIS's is an ongoing project and as the work continues they will be used to answer numerous more questions relevant to the city of Northfield and the Carleton community. If you would like to learn more about some of the GIS resources on campus, check out http://gis.carleton.edu.
