Agriculture Reference
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Fig. 3.1 Example of GIS system
The layout of this chapter is as follows. Section
3.2
describes the main concepts
of GIS and geospatial data models. In Sect.
3.3
, we propose an analysis of GIS data
with particular reference to spatial analysis. Section
3.4
contains a brief description
of GRASS, which is a GIS open source software. Finally, the last section concludes
the chapter with some examples of agricultural GIS applications.
3.2
Introduction to GIS Concepts and Data Models
GIS data describe a simplified digital representation of the earth
s characteristics
for a given study region. Quantitative analysis can be either spatial or a-spatial. In
this topic, the main focus is obviously on the spatial aspects.
In this section, we present and use standard GIS definitions concerning spatial
analysis. For the particular type of spatial data analysis that considers spatial
statistics based on models of phenomena using random variables, we refer the
reader to Sect.
1.4
.
Spatial analysis is generally characterized by three elements: attribute data,
geographical location, and topology. The attributes are
a-spatial
components that
provide the descriptive information of the spatial data. The geographical location
(
spatial component
) is defined using coordinates expressed in a given system of
reference (such as latitude and longitude). Thus, the variables have two types of
different and integrated information: descriptive and geographical information. For
example, a building has geographical (i.e., its position in a territory, or geographical
position) and descriptive (i.e., its typology, attributes) information. Topology is
defined as the spatial relationship between map features.
1
Topology concerns some
'
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