Abstract

Geographical referencing of environmental data is often achieved using a coordinate system such as longitude-latitude or some planar projections. Each variable of interest is measured at a point whose coordinates are assumed to be fixed. Such data are referred to as point-referenced data. This is to be contrasted with areally-referenced spatial data which arise as aggregates or summaries over regions or areas such as states, counties, zip-codes, census tracts and so on. Point-referenced data are often referred to as geostatistical data due to their long history in geological sciences and are perhaps most conspicuous in the environmental sciences today. This chapter presents some essential exploratory and modeling tools for point-referenced data. More detailed and comprehensive treatments for spatial modeling and data analysis can be found in numerous texts such as [8], [7], [16], and [3].