Spatial Analysis Based on Raster Data Processing - Introducing Geographic Information Systems with ArcGIS - page 453

CHAPTER 8 OVERVIEW

IN WHICH you move into an
entirely different realm of GIS
analysis and geoprocessing: solv-
ing problems with a method of data
representation—called raster, grid,
or cell-based—that is dramatically
different from what you are used to.

Spatial Analysis
Based on Raster Data
Processing

Raster is faster but vector is
corrector. Berry, JK, 1995

A Really Different Processing
Paradigm 1
You have briefly met rasters before in this topic. Most images
are stored in raster format. The COLE_DEM of Chapter 1
stored elevations in floating-point raster format. And you
saw rasters that stored landcover in integer raster format.
What is new here is that you will do GIS analysis using raster
representation.

To be candid, it would take another book the size of this one to
cover the immense subject of raster processing. Up until a
few years ago, it was almost completely divorced from GIS
vector processing. Esri has done a good job in taking down
the barriers between the two. In terms of GIS data model
development, raster processing (or grid processing, or
cell processing, which are other terms for it) preceded vector
processing. It was, at one time, about the only way to get large
amounts of geographic data into the memories of the then-
small computers. (100 Kilobytes of storage was a lot in 1960.) In
the following years vector processing, with its greater capacity
for precision, tended to supersede raster processing in terms of
popularity for solving GIS problems. It is now understood that
raster processing has some properties that make it better for
some applications than vector processing. Specifically, analysis
is why GIS analysts use it now—instead of just its advantages
in speed of computation, and, sometimes, conserving
computer memory. Since you now have considerable

1 As you have probably inferred by now, in GIS, “paradigm” is used to
describe a method of storage of geographic data. In the larger view it is
a set of concepts and practices that constitutes a way of viewing reality,
usually for a particular discipline.