By Len Kne
U-Spatial provides support for spatial research. We make maps. And help colleagues at the University of Minnesota discover and analyze geospatial data. We collaborate with people in public health, nursing, business, history, anthropology, education, design, engineering, natural resources, and even dentistry. Thanks to popular apps like Google Maps, billions of people are thinking spatially and becoming more aware of geography throughout the world.
There are countless ways to think about the geography of the Mississippi River. In physical terms, we can, for example, look at tributaries, watersheds, water flow, and water quality (figure 1). In human terms, the river crosses countless cities and neighborhoods, and it shapes transportation, utilities, agriculture, land ownership, commerce, demographics, and zoning. While maps are a great way to show how we interact with the river, getting started with mapping can be daunting. This article will introduce you to some resources that can help.
Geographic Information Systems (GIS) aid in the collection, maintenance, storage, analysis, output, and distribution of spatial data and information (Bolstad 2005). Most of us are familiar with spatial data through our use of Google Maps. Spatial data can be defined as information that has coordinates (i.e., latitude and longitude), as well as attribute data. GIS takes spatial data and creates a model of the real world that we can use to perform analysis, answer questions, and, yes, make maps.
Three core concepts go a long way when thinking spatially: layers, scale, and spatial relationships. Spatial information and data are stored in thematic layers that a GIS can mash together to answer questions. Finding data can be challenging; then, once the data are discovered, harmonizing multiple data sources in order to overlay it on a map can be time consuming. A good starting point for finding data is the Borchert Map Library, located at the University of Minnesota. Later in this article, we will introduce ArcGIS Online, another tool for discovery and mapping of spatial data.
Map Scale is an important consideration when representing spatial data. Commonly seen as a scale bar, the map uses a representative fraction to show distance. For example, U.S. Geological Survey (USGS) topographic maps commonly use a 1:24,000 scale, which indicates that one inch on the map is equal to 24,000 inches (2,000 feet) on the ground. The amount of detail we want to show on a map determines how we represent a feature. When looking at the entire length of the Mississippi River, we represent the river as a line. However, when looking at an individual reach of the river, we want to show the width of the river and, thus, display it as a polygon (figure 2).
Spatial relationships define how we interact with the data. Three common spatial relationships are “adjacency,” “within,” and “connectivity.” Minnesota is adjacent to Iowa, Hannibal is within Missouri, and the Mississippi River connects St. Paul and New Orleans. We can use GIS operations to query data using these spatial relationships. For example, how many people live within 10 miles of the Mississippi River in the St. Louis area? We use the buffer tool to pad the river by 10 miles on each side and then the overlay tool to sum the population from a census layer in the buffered area. The answer is 1,935,000 for 2015 (see figure 3 for other selected statistics of the area).
Creating informative maps has gotten easier, thanks to several web-based GIS tools. I like ArcGIS Online because it has a vast collection of data (check out the Living Atlas of the World), as well as the tools needed to analyze the data and make compelling maps that can be easily shared. For example, here is the map used in the St. Louis illustration above. Another example demonstrates a geodesign application that models practices that can improve the water quality of the Minnesota River (figure 4). ArcGIS Online offers a free trial account that allows anyone to explore the world using their tool. Most universities have a license agreement for students, faculty, and staff to access ArcGIS Online. All K-12 schools have free access through the Esri ConnectED program.
The U-Spatial website is a good place to start when looking for help with mapping and spatial analysis. The site provides links to training, data, and GIS tools. Another resource is GeoMentors; they can help bring spatial thinking into the K-12 classroom. Happy mapping.
Bolstad, Paul. 2005. GIS Fundamentals: A First Text on Geographic Information Systems, 2nd edition. White Bear Lake, MN: Eider Press.
Kne, Len. 2016. “Maps, Geographies, and the Mississippi” Open Rivers: Rethinking The Mississippi, no. 2. https://openrivers.lib.umn.edu/article/maps-geographies-and-the-mississippi/.
Download PDF of Maps, Geographies, and the Mississippi by Len Kne.