8.1 Introduction

Computer graphics are stored and processed either as vector or raster data. Most data types that were encountered in the previous chapter were vector data, i.e., points, lines and polygons. Drainage networks, the outline of geologic units, sampling locations and topographic contours are examples of vector data. In Chapter 7, coastlines are stored in vector format while bathymetric and topographic data are saved in the raster format. In many cases, vector and raster data are combined in one data set, for instance the course of a river is displayed on a satellite image. Raster data are often converted to vector data by digitizing points, lines or polygons. On the other hand, vector data are sometimes transformed to raster data.

Images are generally represented as raster data, i.e., as a 2D array of color intensities. Images are everywhere in geosciences. Field geologists use aerial photos and satellite images to identify lithologic units, tectonic structures, landslides and other features in a study area. Geomorphologists use such images for the analysis of drainage networks, river catchment, vegetation and soil types. The analysis of images from thin sections, automated identification of objects and the measurement of varve thicknesses employ a great variety of image processing methods.

This chapter deals with the analysis and display of image data. Firstly, the various ways that raster data can be stored on the computer are explored (Chapter 8.2). Subsequently, the main tools for importing, manipulating and exporting image data are presented (Chapter 8.3). This knowledge is...