Geographical information systems
(GIS)
Вонр. проф. д-р Александар Маркоски
Технички факултет – Битола
2008 год.
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Introduction
“A computer based system, consisting of hardware, software,
data and application. It provides scientific information
considering spatial relation.
A GIS has to offer functions for
– input,
– storage,
– checkup,
– manipulation,
– integration,
– analyzing and
– alphanumeric as well as graphic presentation of spatial
data.
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Introduction (2)
• The integration of thematic data and information about the
spatial situation (which will be presented cartographical),
distinguishes a GIS from a mere cartographic- or CAD(Computer Aided Design) system.” (Weidenbach, 1999)
• GIS is not only a tool for making maps, it is a system for
data analysis!
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Other definitions for GIS
• The common ground between information processing and
the many fields using spatial analysis techniques
(Tomlinson, 1972).
• A powerful set of tools for collecting, storing, retrieving,
transforming, and displaying spatial data from the real world
(Burroughs, 1986).
• A computerized database management system for the
capture, storage, retrieval, analysis and display of spatial
data (NCGIA, 1987).
• An information system that is designed to work with data
referenced by spatialor geographic coordinates. In other
words, a GIS is both a database system with specific
capabilities for spatially referenced data, as well as a set of
operations or working with the data (Star and Estes, 1990).
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Тerm GIS
The term GIS has different meanings.
Depending on the focal point it is:
–
–
–
–
a collection of spatial data
a collection of tools
a package of hard- and software components
a technology
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Contributions to GIS-development
• Informatics (graphic, visualization, data base, security,
system administration),
• geography and related fields (cartography, geodesy,
geomorphology, spatial statistics)
• user (public administration, engineering, location search,
planning, geology, mining, forestry, marketing, criminology)
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Visualization of Data
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Elements of a GIS
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The four-components-model of a GIS
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Which Operations can be done with a
GIS ?
•
•
•
•
•
What is where?
Where is what?
What has changed since...?
How is the spatial spread?
What happens if...?
GIS uses the spatial allocation as a common key for different
data records. Different issues are connected by their
geographic position.
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Steps in a GIS project
1. Data acquisition (paper maps, digital files, remote sensing
data, satellite data, field work),
2. Data preprocessing (preparation, integration, data
conversion, digitising and/or scanning, edge matching,
rectification),
3. Data management (variable selection, data definition,
table design (performance, usability), CRUD
policies/procedures (create: data entry; retrieve: view;
update: change; delete: remove)),
4. Manipulation and analysis (address matching, network
analysis, terrain modelling: slopes, different aspects),
5. Product generation (tabular reports, graphics: maps,
charts).
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What should be possible with a GIS?
• Management, analysis, connecting, presentation of geographic
data allows:
• automatic processing of geographic data, for example for making
maps,
• calculation of areas or distances
• calculation of slopes, exposition direction or visibility analyses,
• route planning, traffic management or logistics
• integration of data of different origins and types
• linkage of data to maps, to make complex spatial relations visible
• to answer spatial questions (for example: How many objects are
within a given distance to another object ?)
• the spatial modelling of complex scenarios (risk analysis, route
planning, resource management)
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System architecture and components
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Data Models
• What should a GIS represent?
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Data Models (2)
Discrete Objects have
attributes as
• length
• volume
• land use
• type
Continuous Information for
an area has gradients as :
• temperature
• content of water
• distribution of precipitation
• content of contaminants
Depending on the data concept there are raster/Grid-GIS or
Vector-GIS. Systems working with both types, are named
hybrid systems.
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Data Models
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General Structure of a Grid
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Vector Data
• The vector-structure is necessary for a object-related data
management in GIS. It is used for the realization of
topologic structures and complex data models.
• Objects in Vector-GIS are points, lines, polygons.
• Every GIS-object in a view has a representation in the data
base. The attributes describe the objects and allow
selections and classifications.
• Classification by attribute (above) or selection by attribute
(below) are typical Data Base Management Methods.
Selection or classification by spatial relations are typical
GIS-methods.
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Vector GIS Objects
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Atributes
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Selecting objects
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Selecting
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Vector vs. Raster
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Raster vs. Vector
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Representation of Vector Data as
Raster Data
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Modelling topography special features
• Mass points and break lines from surveying,
• Triangulated irregular networks (TIN),
• 2,5-D Visualisation: Hillshading,
• Colour coded digital terrain model (DTM),
• 3-D Visualisation.
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Grid data model
• Digital Elevation Model (DEM) in the background, showing the elevation,
using graduated colors and shadows for visualizing 3rd dimension. In
the foreground houses and water body (river) are shown, using vector
data model.
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Triangulated Irregular Network
• Base for developing the DEM (above) is a Triangulated
Irregular Network (TIN), based on measured points
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1
3D-Presentation of a the
same TIN, example for
vector based
representation of a surface
• irregular size of triangles,
• areas with higher and lower
density of knots
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2
3D-Presentation of a grid, showing
the same area (but different point
of view)
• regular cell size
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3
Combination of grid model
(surface) and vector model
(houses)
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Example for high resolution grid
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Example: Visualization of water quality
data, using polygons
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Example: Visualization of water quality data,
using polygons (cont.)
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Fields of applications of GIS
• Automation of activities involving geographic data like map
production, calculation of areas, distances or route lengths,
measurement of slopes, aspect, view shed, logistics, route
planning, vehicle traffic, traffic management, land use
management, environmental planning, flood control, resource
management, and others.
• Integration of data hitherto confined to independent domains (e.
g. Property maps, air photos).
• tying data to maps permits the succinct communication of
complex spatial patterns (e. g. environmental sensitivity).
• providing answers to spatial queries.
• performing complex spatial modelling (e. g. scenarios for
transportation planning, disaster planning, utility design, risk
modelling).
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Use of GIS in practical and research
fields
• Environmental and resource management (Watershed
management, soil conservation, air pollution control,
agriculture, water harvesting, water supply),
• Urban planning, management and policy (Land
acquisition, environmental impact assessment),
• Surveying,
• Facility management (Infrastructure, telecommunication),
• Transport, Traffic, Logistics,
• Research and development (Environmental modelling,
simulation and optimisation of energy, soil, water, climate,
etc. for risk assessment and decision support).
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Scientific and engineering contributors
to GIS
• Geography (provides techniques for conducting spatial
analysis),
• Cartography (maps have been a major source of
information input for GIS, long tradition in map design which
is an important output from GIS),
• Remote sensing (images from air and space are major
sources of spatial data, low cost and consistent update of
input data),
• Photogrammetry (source of most data on topography used
in GIS, uses aerial photographs for making accurate spatial
measurements, IR photographs),
• Surveying (provides high quality data on positions of land
boundaries, buildings, etc.),
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Scientific and engineering contributors
to GIS (2)
• Geodesy (high accuracy positional control for GIS, uses
GPS technology),
• Statistics (statistical techniques used in GIS analysis,
important to understand issues of error and uncertainty in
GIS data),
• Operations research (optimising techniques used in GIS
applications such as routing),
• Computer Science (GIS uses computer aided design
(CAD) technologies, computer graphics and visualisation,
DBMS).
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Software for GIS
• ArcInfo (Originated commercial GIS, clear market leader),
• Intergraph (Strong in design and facilities mapping, running hard
to match ArcInfo, its main modular GIS environment evolved from
its older CAD products, development of a new generation product
of ist own code named Jupiter based on NT and object
technology)
• Bentley Systems (Originally developed the PC-based MicroStation product GeoGraphics in cooperation with Bentley
Systems, but split in 1995, have very successfully continued to
develop and sell MicroStation GeoGraphics)
• Autodesk’s AutoCAD Map (Dominant CAD supplier and
software company, fully topological AutoCAD Map since 1996,
illustrates convergence of CAD/GIS, many industrial applications
of AutoCAD for mapping)
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Software for GIS (2)
• Graphic Data Systems (Originated as McDonnel-Douglas inhouse system, industrial applications, visualisation of technical
products, now mapping the environment)
• ERDAS/Imagine, ER MAPPER, PCI, Envi (Origins in remote
sensing raster and vector data, new satellite data products, ER
MAPPER originating in Australia, PCI originating in Canada)
• GRASS (Public domain software, raster oriented with some vector
routines, but 1996 end of development and support announced),
• SICAD (Comparable with ArcInfo, powerful GIS with a lot of
functionalities for raster and vector data, object oriented
database)
• IDRISI (Comparable with ArcInfo, but not so powerful),
• MapInfo (Small GIS, useful for planning purposes, easy to
handle)
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Problems in GIS practice
Up to now, there is no system that could solve all possible
tasks a GIS normally is confronted with:
• there is no unique data model that serves well for all GIS
applications,
• there are no fully compatible geodata,
• there are no scale-independent geodata,
• there are no fully compatible/applicable commercial systems
of data formatting,
• there are still severe problems with data exchange,
• there are some deficits in standardisation of GIS.
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GIS Application Example:
Hydrological Modelling using ArcView
• 1. Creating a DEM from point
data file
• 2. Creating river network
• 3. Creating sub-catchments and
pour points
Example is based on ArcView
3.x, with Spatial Analyst, 3DAnalyst and Hydro-Modeling
Extension
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Creating a DEM from point data file
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Hydro-Modeling
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Flow direction
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Flow accumulation
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sub-catchments
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Questions?
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