Geographical Information Systems - Part 2

Objects in geographic space are modeled as discontinuous spatial phenomena whose properties are defined according to the geometric, thematic and spatial dimensions: geometric. The properties of these spatial objects can be described by different indices that characterize an object’s shape, size, spatial distribution or even its spatial dependence. When considered simultaneously, in conjunction with the study context, these indices describe the landscape under investigation.

A phenomenon is considered spatially continuous if it is defined at all points in geographic space, and if its properties vary locally in a gradual and structured manner. Elevation, soil humidity, heavy metal concentration and other soil contaminants are common examples of continuous spatial phenomena. This module will begin by touching on different sampling methods, then deterministic interpolation methods that do not require any a priori study of the phenomenon. Working to the heart of the lesson, we will then introduce geostatistics, which are based on the notion of random functions, and we will finish by discussing the concepts and application of regionalized variables, variogram analysis and kriging.

Topographical relief plays both a revealing and explanatory role in determining the way phenomena unfold on the Earth’s surface. It constitutes an important element in the determination of human settlement patterns and also controls environmental conditions that favor, or hamper, the establishment and development of different plant and animal colonies. Correspondingly, relief occupies a central position in spatial analysis and is important for any discipline that is interested in human activity or natural phenomena. This chapter will present a brief overview of the different methods used to acquire elevation data and will also cover the algorithms, and their properties, that are used to derive important descriptive indicators of relief.

Through spatial overlay, GIS can be used to combine data from different sources or in different formats (raster or vector) by transferring information between layers according to their spatial relationships. Often the analysis of geographically distributed phenomena requires that data from different sources can be considered simultaneously. This is made possible through spatial overlay - the defining functionality and primary advantage of geographic information systems.