VISUALIZING POINT DATA ACROSS LANDSCAPES IN A GIS: EXAMPLES FROM LOESS DEPOSITS IN THE NORTHERN GREAT LAKES REGION

We present several ways, both established and new, to visualize point data in a GIS, so as to facilitate interpretations. The data were collected as part of a larger study of loess deposits across the upper Great Lakes region. We use this poster to highlight the various ways in which data can be visualized, using contemporary cartographic techniques. Because these methods can be used with any kind of point data, they have potentially wide application within the Earth Sciences.

Our analysis included textural and thickness data for >450 loess samples from northeastern Wisconsin and Michigan’s western Upper Peninsula. Loess here was derived from several large outwash plains that formed during ice retreat, as well as more localized sources such as valley trains or disintegration moraines. Previous work has established that most of this loess, because it was strongly influenced by local sources, has complex spatial patterns that change rapidly over short distances. This stands in contrast to the loess of the southern Great Lakes region, e.g., in Illinois, which was derived from one main source and which has smooth and predictable spatial trends that span large distances.

In previously published papers on the loess of this region, the data were presented only as filled isoline maps, developed via kriging. In this poster, the data, again presented as filled isoline maps, are compared using graduated circle maps, as isolines, and as terrain inclusive maps. Our goal is to highlight the various ways in which point data can be visualized, thereby showing the strengths and weaknesses of each presentation method. The data are also intended to show how interpretations may be affected by the manner in which the data are displayed. We hope that this poster will facilitate discussion not only of GIS and cartographic symbology, but also generate ideas as to details of the loess depositional systems in the region.