Purdue University Students Visualize Soils and Landscapes with GIS
Understanding how soils form in the field and vary across landscapes is a critical skill for today's agronomists; therefore, it is an integral component of the curricula at Purdue University in Indiana. Students use GIS in the classroom and in the field to better understand soils and landscapes and to recognize geologic features that indicate different soil types.
Soil Classification, Genesis, and Survey, a class cotaught by professors Darrell G. Schulze and Phillip R. Owens, incorporates the latest GIS software to study the relationships between soils, topography, land use, and geology. The teachers use GIS to share data with the students, who in turn use it to observe different points in the landscape. At the beginning of the class, most students know little about geography and GIS, but by the time they complete the course, they are able to access geographic data and view it with GIS tools.
Schulze accesses the United States Department of Agriculture (USDA) soil survey data, as well as data from the Indiana Spatial Data Portal and the Indiana Geological Survey. "This data is robust," notes Schulze. "In 2007, USDA completed digitization of soil data for Indiana, so I can access soil data for any county in the state." Schulze takes on the task of downloading this data, along with high-quality aerial photography and high-resolution digital elevation models (DEMs). Using GIS to aggregate the data in various ways that fit class objectives, he creates a variety of useful data files. For example, he created a dominant soil parent material model that groups polygons together so that students can see relationships not readily apparent from traditional representations of soil survey data.
Longtime users of ArcGIS, Schulze and Owens have their students visualize the geomorphology of their study area with GIS. "Students easily relate to the features they can see while they are standing in a field; however, larger landscape features that occur over kilometers are much more difficult to immediately understand," explains Owens. "Teaching soil geomorphology using Tablet PCs and GIS provides the students with tools to see patterns over large distances and has revolutionized our ability to teach spatial relationships."
Students can see, for instance, that Purdue is located in a part of the world that was glaciated 20,000 years ago and understand close correlations between the soil parent material and the surficial geology. DEMs highlight relevant topographic variations. By comparing this with soil data, students make conjectures about how geologic phenomena have affected soils. They can see, for example, that soils formed on dense glacial till that was smeared down and compacted by the ice as the glacier moved along its path are wet because the water cannot move readily through the dense material. Sandy and gravelly soils that formed on the outwash that was deposited by the rapidly running water from the melt are better drained, and they do not have a high water table in the winter like the soils on glacial till. GIS shows how the difference in the internal soil drainage class of those soils is influenced by the different parent soil materials.
By projecting the desktop onto a screen, the teacher demonstrates GIS operations in the classroom. Students become familiar with basic viewing features, such as zoom in and pan and toggling layers on and off, as they begin to review datasets and relationships.
During the normal weekly three-hour lab periods, the class goes on short, local field trips near campus. Students take along assigned ruggedized Tablet PCs, which are loaded with ArcGIS Desktop and integrated with GPS, as they drive to locations near campus. There, they examine soil pits to study soil types.
Later in the semester, there are two all-day field trips. Students travel by bus from West Lafayette, Indiana, north to Lake Michigan on the first trip and as far south as Bloomington, Indiana, on the second. Class time is continued while traveling on the bus, and students are literally oriented as they follow their routes via the GPS and ArcGIS interface on their Tablet PCs. The bus has a monitor on which the teacher continues to teach soil-to-geology relationships.
Students can explore the lesson and make observations on their Tablet PCs. "While we are traveling to our destination, I use GIS to display the outcome on a monitor mounted in the bus," says Schulze. "We can show them how to read the landscape. They learn that a slope or a particular shape of a hill was formed by a particular geomorphic process and can then deduce the material that is underneath. They learn to recognize, for instance, an esker, which is a long, skinny hill that has sand and gravel under it where there was once water flowing under the ice. Using their Tablet PCs, they can compare the virtual esker with the reality of the landscape. GPS indicates, in real time, where they are on the map, verifying their interpretation of what they are seeing. Using these tools in the field makes topics much clearer than trying to understand the material from a textbook, where these connections are more abstract."
Purdue is located in Tippecanoe County. In the western half of the county, a lot of the soils have been formed under prairie vegetation, giving them dark-colored surfaces. In the eastern half of the county, soils formed under forest vegetation and have a lighter color. The prairie soils tend to be slightly better for growing crops because they are higher in organic matter and, overall, the topsoil has better physical properties. Forested soils are more prone to crusting. This type of soil identification can help agronomists predict yield. These delineations are made obvious to students out in the field who can make map to reality comparisons.
Newly released data, map products, and models continue to advance with each new class. Schulze is currently working on an application in which students can click a polygon to query the attribute table as well as click a link that leads them to a schematic diagram of a soil profile that illustrates what the soil looks like below the surface.
"Two approaches can be taken in using GIS for education," explains Schulze. "One is teaching about GIS and how it works, and the other is using GIS to teach particular concepts. In the latter, teachers design maps for students, working them into a format that works well for the specific class. The data is preassembled and put into a format that works easily for the student and helps the teacher focus precisely on the topic. Hands-on use of GIS-loaded Tablet PCs reinforces concepts from the lecture. GIS is helping us teach concepts in our class that would otherwise take students years of field experience to acquire."
For more information, contact Darrell Schulze, professor of soil science, Agronomy Department, Purdue University (e-mail: firstname.lastname@example.org).