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Geographical information systems (GIS)

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Title: Geographical information systems (GIS)


1
Geographical information systems (GIS)
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  • ???????? ???????? ??????
  • 2008 ???.

2
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.

3
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!

4
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).

5
?erm 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

6
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)

7
Visualization of Data
8
Elements of a GIS
9
The four-components-model of a GIS
10
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.

11
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).

12
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)

13
System architecture and components
14
Data Models
  • What should a GIS represent?

15
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.
16
Data Models
17
General Structure of a Grid
18
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.

19
Vector GIS Objects
20
Atributes
21
Selecting objects
22
Selecting
23
Vector vs. Raster
24
Raster vs. Vector
25
Representation of Vector Data as Raster Data
26
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.

27
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.

28
Triangulated Irregular Network
  • Base for developing the DEM (above) is a
    Triangulated Irregular Network (TIN), based on
    measured points

29
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

30
2
  • 3D-Presentation of a grid, showing the same area
    (but different point of view)
  • regular cell size

31
3
  • Combination of grid model (surface) and vector
    model (houses)

32
Example for high resolution grid
33
Example Visualization of water quality data,
using polygons
34
Example Visualization of water quality data,
using polygons (cont.)
35
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).

36
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).

37
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.),

38
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).

39
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 Micro-Station product GeoGraphics in
    cooperation with Bentley Systems, but split in
    1995, have very successfully continued to develop
    and sell MicroStation GeoGraphics)
  • Autodesks 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)

40
Software for GIS (2)
  • Graphic Data Systems (Originated as
    McDonnel-Douglas in-house 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)

41
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.

42
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, 3D-Analyst and Hydro-Modeling Extension

43
Creating a DEM from point data file
44
Hydro-Modeling
45
Flow direction
46
Flow accumulation
47
sub-catchments
48
Questions?
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