USING IMAGES WITHIN A GIS FOR SPATIAL ANALYSIS 
Eugene Derényi, Honorary Research Professor 
David Fraser, Research Assistant 
Department of Geodesy and Geomatics Engineering 
University of New Brunswick 
Fredericton, N.B., Canada E3B 5A3 
Commission IV, Working Group 1 
KEY WORDS: GIS, Database, Image, Raster, Vector, Spatial Analysis, Image Classification, Database Query 
ABSTRACT 
A universal geographic information system (UGIS), in which both vector based cartographic data and raster based 
continuous tone image data can be processed and managed, open new possibilities for performing spatial analysis. The 
software tools developed in this environment allows to: 
issue location specific database queries through an image display without the superimposition of the vector based 
geographic data; and 
* extract location specific thematic information from images based either on per-pixel classification or on image 
statistics. 
The information generated with the help of these analysis tools can directly be entered into the database. 
1. INTRODUCTION 2. GEOGRAPHIC DATA 
REPRESENTATION 
Geographic information is a collection of facts, about a 
geographic entity, that has been organized so that it 2.1 Maps 
conveys some meaning or significance. The 
information associated with a geographic entity has 
four major components [Aronoff, 1989]: i) geographic Mapping involves several processing operations, two 
location; ii) attribute(s); iii) spatial relationships; iv) of which are data abstraction (or generalization) and data 
time. In other words, the four components define reduction. These steps are used to create a model of the 
where the geographic entity is, what it is, what its spatial phenomena of interest which is easier to 
relationship with its surroundings is, and when was it understand than the real world. As a result, certain 
observed. The two most commonly used form of portions of the data gathered of-the-real world are 
geographic data representation is the map and the ignored or obscured, while others are. enhanced to 
image. There are distinct differences between these two generate a product which meets the requirements of 
data representations which impacts on their function users. Nevertheless, maps are useful for portraying 
and utilization in spatial analysis. information about the real world because they can 
succinctly describe a phenomena, can be easily 
During the era when all geographic information was understood and can provide spatial reference when 
represented in hardcopy form, the two types of products making decisions regarding a phenomena. Typically, a 
were distinctly separated as cartographic line maps and map depicts either a specific spatial characteristic or a 
orthophoto maps. In the softcopy world this certain theme. In the digital world the information can 
distinction in the two forms of geographic data easily be separated into layers. This approach of 
representation exists as digital vector data and raster isolating the real world into layers, is useful for 
image data. Advanced geographic information systems examining spatial relationships that exist between 
(GISs) allow the co-existence of the two data various themes and the spatial patterns which 
representation forms. Thus, the challenge is to exploit characterize these themes. 
the advantages of both and to devise innovative 
methods for doing so. The spatial analysis scheme Even though maps have proven to be an effective tool 
described in this paper is a step in this direction. First, in spatial information management, there are several 
however, a short discussion on the characteristics of weaknesses associated with using maps as information 
these two forms of data representation is presented. sources, for making decisions regarding the real world. 
These problems have been well documented (e.g. 
[Unwin, 1981], [Trotter, 1991]) and can be briefly 
summarized as follows: Maps are static and often out- 
dated even before they are incorporated into a 
geographic database. Even though each map is à 
generalization of the real world, displaying all map 
layers of a multi-layer geographic database at once in 
216 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996 
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