Volume 3. No 3
Information Technology News of the University of California, Davis Spring 1995
Information Technology News of the University of California, Davis Spring 1995
Since UCD established a beginning Geographic Information Systems class in the spring of 1994, students have been applying the ARC/INFO software to a wide range of disciplines.
Student projects have included a study of cheetah migration in Africa, flood plain analysis of Sacramento county, and an examination of the influence of topography on medfly distribution in Los Angeles county. What do these projects have in common? They all depend on data that can be expressed spatially, producing an image that can then be manipulated and analyzed - using software like ARC/INFO significantly reduces the amount of time that researchers have to spend "massaging " their data, leaving them free to spend more time to analyze their results.
This quarter, UCD has introduced an advanced GIS class - Applied Biological Systems Technology 198. It is team taught in the Visualization Laboratory by Wes Wallender of Hydrologic Science and Paul Grant of Information Technology, with assistance from Glenn Fitzgerald, a graduate student in Agronomy & Range Science. Where the beginning class focuses on the analysis of data stored and displayed using vector graphics, this new class takes advantage of ARC/INFO's grid module, which allows students to create and analyze raster datasets as well.
Vector graphics, which are composed of arcs, lines, and irregularly shaped polygons, take up less file space than raster graphics; but creating graphical overlays with vector images can be a lengthy process, requiring complicated algorithms. Raster graphics, on the other hand, tend to require more storage space, but because they are laid out on a grid, calculations based on data expressed in raster form are much quicker.
"Neither is necessarily better or more accurate, " says Grant. "There are certain tasks which are easier to perform using rasters, and there are situations where each type of image has its advantages. For example, raster-based GIS would be used when representing a continuous variable, such as elevation, slope or aspect. "
Students in the advanced GIS class not only learn more advanced analysis techniques using ARC/INFO, they are also taught to use Data Explorer, a scientific visualization software package from IBM that allows students to take the same data that they would analyze in ARC/INFO and express it in three or four dimensions.
Data Explorer expresses data in three dimensions by plotting data to create three- dimensional shapes; the program expresses data in four dimensions in two ways: either by plotting three of the data sets as a three-dimensional surface and then mapping the fourth data set onto that surface, or by plotting three data sets as a three-dimensional shape and then showing their progression through time via animation. In order to run Data Explorer, I.T. has expanded the Visualization Lab to include five Silicon Graphics Indy workstations, which contain hardware for quicker processing and manipulation of graphics.
For more information about GIS, you can contact Paul Grant at 752-8266 or via e-mail at pwgrant@ucdavis.edu.
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