Impact of multi-scale predictor selection for modeling soil properties

Results suggest that models with limited predictor pools can substitute other predictors to compensate for unavailable variables. However, a better performing model was always found by considering predictor variables at multiple scales. Although the scale effect of the modifiable area unit problem is generally well known, this study suggests digital soil mapping efforts would be enhanced by the greater consideration of predictor variables at multiple analysis scales.

Accuracy vs Precision

Scientists often measure and predict things. Therefore, we need ways to describe how much we know, how close a number is to reality, and how likely we are to get the same number again. The terms accuracy and precision are generally used to describe these things, but there can be some ambiguity. This post explains …Continue reading “Accuracy vs Precision”

Types of Scale

When you read the phrases “large scale” or “small scale,” do you know what they mean? Sometimes “large scale” is describing a large area and sometimes it is describing a small area, depending on if the author was thinking about process scale or cartographic scale. This is a problem for communication. In this post I …Continue reading “Types of Scale”

Fundamentals of Spatial Prediction

In the process of creating a map, geographers often have to engage in the activity of spatial prediction. Although there are many tools we use to accomplish this task, they generally boil down to the use of one or two fundamental concepts. Waldo Tobler is credited for identifying the ‘first law of geography’, stating “Everything …Continue reading “Fundamentals of Spatial Prediction”

Pre-settlement Water Regimes of Iowa Wetlands

This raster provides an estimate of the wetland water regimes in Iowa, prior to the implementation of drainage systems. These estimates are based on the spatial information in the USDA-NRCS gSSURGO database and soil series characteristics described in the official soil series descriptions (OSD). Soil series characteristics were matched as best as possible to the …Continue reading “Pre-settlement Water Regimes of Iowa Wetlands”

Physiography of the Des Moines Lobe

This GIS package contains a pair of spatial data sets that have been generated for the purpose of studying the physiography of the Des Moines Lobe landform region. One is a surficial geology map of the Des Moines Lobe and surrounding areas. This raster was generated from the USDA-NRCS gSSURGO spatial database. The attributes were extracted from …Continue reading “Physiography of the Des Moines Lobe”

The historical role of base maps in soil geography

This paper reviews the historical development of base maps used for soil mapping, and evaluates the dependence of soil mapping on base maps. Formerly, as a reference for spatial position, paper base maps controlled the cartographic scale of soil maps. However, this relationship is no longer true in geographic information systems. Today, as parameters for digital soil maps, base maps constitute the library of predictive variables and constrain the supported resolution of the soil map.

The Cycle of Science

In an earlier post I contrasted induction and deduction while suggesting that induction is the currently favored term used in science. However, I also suggested that the two philosophies can be used in concert with one another. Indeed, as much as one can argue about the virtues of one philosophy or the other, science actually advances …Continue reading “The Cycle of Science”

Why Geography?

The scientific discipline of geography has taken on many important topics over the course of its history. From locating natural resources, to understanding the intricacies of human cultures in diverse locations, to predicting climate change and its impacts on society, geography has helped us better understand our world. Students in grade schools are taught basic …Continue reading “Why Geography?”