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Title:

GIS

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the user himself or herself becomes also a part of the ... overlapping map layers road. real world - GIS software can be used to. create thematic maps based ... – PowerPoint PPT presentation

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Title: GIS


1
GIS
Introduction to GIS

Tino Johansson GISAS project Department of
Geography University of Helsinki Finland
2nd GISAS project meeting in Helsinki, 13 May 2004
2
Geographical Information Systems (GIS)
  • Computerised systems for
  • managing, storing, visualising
  • and analysing spatial
  • information
  • locate information on the
  • basis of coordinates
  • coordinate-based location
  • is the unifying feature between
  • different types of information
  • and map layers

3
Geographical Information Systems (GIS)
  • the system does not only mean the GIS software
    itself, but consists also of the hardware and
    data we are using
  • the user himself or herself becomes also a part
    of the system when he or she is using the GIS
    software and data

hardware
GIS
data
software
user
4
Geographical Information Systems (GIS)
  • map layers containing information
  • registered in the same coordinate
  • system can be used to carry out
  • overlay analyses
  • reveals interactions between
  • different spatial objects
  • visualised with symbols, lines
  • polygons and raster images
  • inquiry-based learning
  • What? Where? Why? When?

Water quality
Households
Land-use
Sanitation
Tourism
Economy
Hazards
Habitats
5
Geographical Information Systems (GIS)
  • GIS software visualises
  • real world situations with forest
  • different types of spatial houses
  • objects located into lake
  • overlapping map layers road
  • real world
  • - GIS software can be used to
  • create thematic maps based
  • on attribute tables of the
  • spatial objects

6
Vector type data
  • the basic structure is a point, which is located
    by X and Y coordinates on a coordinate system
  • lines are formed by a number of points and
  • polygons are lines which start and end at the
    same coordinate point

a point has defined X and Y coordinates (x1y1)
a line is built up of a row of points
(x1y1, x2y2,xnyn)
a polygon is a closed line, which begins and
ends at the same point location (x1y1, x2y2,x1y1)
7
Vector type data
polygon
line
point
8
Raster type data
  • raster images display the real world situation
    with square shape figures stored in rows and
    columns
  • these figures do not have x and y coordinates but
    are located according to their place in the
    raster rows and columns

contour line
house
road
field
9
Raster type data
field, yellow
road, black
C
D
A
B
1
2
3
4
river, blue
house, black
10
Data structure
Each vector object on the map window has one row
on the attribute data table.
11
Data structure
Each vector object on the map window has one row
on the attribute data table.
Each types of vector objects are stored
on different map layers and attribute tables.
12
Data structure
  • GIS data is a combination of map data and
    attribute data
  • these two data are linked with georelationality
  • attribute table data is used to create thematic
    maps on the map window
  • GIS software is also able to locate features on
    the map according to the coordinate data on the
    attribute table
  • For example, the BISEL water quality analysis
    points on the river are located with the help of
    GPS receivers. the X and Y coordinates of each
    location are stored on the attribute table with
    other types of data from those locations, such as
    Biotic indexes. Later those coordinates may be
    used to visualise the points on the local map.

13
Map data
  • contains information on
  • the coordinates (X, Y, Z) of the map objects
  • the used coordinate system
  • the geometry of the map objects (points, lines,
    polygons)
  • topology (neighbourhood, connectivity, relation
    to other objects)

island
line 1.
lake
line 2.
14
Attribute data
  • contains information on
  • the identification of the objects (typically a
    rank order number)
  • the georeferencing data (postal code, street
    address)
  • the date, time or year (places the attribute on a
    time-scale)
  • the descriptive data (other attributes of the map
    object, such as forest type, Ph-level, depth of
    the water etc.)

15
Asking geographical questions
  • GIS software is often used for asking questions
    about locations (where something is?) and
    contents of the locations (which map objects have
    certain attributes?)
  • asking such questions is called querying in GIS
    vocabulary
  • queries can be carried out on the basis of one or
    more attribute tables
  • GIS software is an efficient tool for supporting
    regional decision making and creating what-if?
    scenarios
  • GIS use is expanding in societies around the
    world and soon becomes part of our daily lives,
    too
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