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1106: Geographical Information: a primer

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1106: Geographical Information: a primer Communicating with Cartography 29/10/2004 TOPICS How does a map communicate? Thematic maps Topographic information Abstract ... – PowerPoint PPT presentation

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Title: 1106: Geographical Information: a primer


1
1106 Geographical Information a primer
  • Communicating with Cartography
  • 29/10/2004

2
TOPICS
  • How does a map communicate?
  • Thematic maps
  • Topographic information
  • Abstract maps
  • Geographical Information Systems
  • Practical info for NEXT WEEK

3
How does a map communicate?
  • Real word features are represented as points,
    lines, polygons, contours and symbols
  • A map conveys a wide range of characteristics
    about the real world
  • Size, length, distribution, patterns, contiguity,
    neighbourhood, space, shape and orientation

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Thematic maps
  • Perhaps we should say - What do maps communicate?
  • Thematic means theme based and a map can
    graphically communicate the spatial variability
    in a wide range of possible themes - both human
    (socio-economic) and physical

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Thematic Maps
  • Population, death-rate, income levels etc are
    dynamic themes of data that will change rapidly
  • Soils, geology, ecological zones and political
    maps will remain fairly static
  • Themes may be presented as different colours or
    dots/shading - or even small pie-charts overlaid
    onto a normal political map

9
Topographic maps
  • Contours show areas of equal height above mean
    sea-level (MSL)
  • Contours close together represent steep changes
    in height - contours far apart show gradual
    change in height
  • Contours use an interval (in metres) although not
    all contours may be labelled

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Using contour maps
  • Locate the nearest line to your feature
  • If not labelled, locate nearest labelled line and
    multiply number of contours away by the interval
    then add (or subtract) this value from the
    nearest labelled contour value
  • An alternative to using contours is a
    3-dimensional rendering of the surface

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Abstract Maps
  • Maps do not always have to be accurate in terms
    of their representation of reality
  • Maps can be abstract and may represent features
    of the real world in an ethereal way
  • Maps can be used to suggest connections,
    principles or ideas that bear no parallel in
    reality. Such en entity is known as a cartogram

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Abstract maps
  • Any kind of information can be communicated by a
    map
  • Just as the London Underground was designed by an
    electronics draughtsman (Beck) in the 1920s, maps
    can be used to show power distribution - using
    clever abstraction and use of symbols

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Abstract maps
  • Maps can also be used to provide a graphical
    representation of forecasts
  • A map of a forecast variable (rainfall or
    temperature) is interesting as no such feature
    actually exists in reality.

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Abstract Maps
  • Maps do not have to be 2 dimensional
  • Detailed surveys of towns and cities have allowed
    computer generated 3-dimensional renderings to be
    generated

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GIS
  • Geographical Information System (GIS)
  • A GIS allows layers of spatially referenced
    information to be combined as though they were
    transparent slides
  • A GIS can drill down through these layers to
    perform calculation, scenarios and model
    solutions to complex problems

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GIS
  • A GIS must have a spatial reference framework.
    This can be latitude/longitude, Ordnance Survey
    grid, postcodes etc
  • A GIS operates entirely within a computer system
  • VECTOR features are represented as POINTS, LINES
    and POLYGONS

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GIS
  • Some map data is continuous and is created from
    pixels. This type of data is known as RASTER data
  • Raster data can be derived from satellite
    (rainfall, vegetation or a an aerial photograph)
  • Raster data can be used in complex environmental
    models

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GIS
  • Can be used for real-time applications
  • Vector data stores metadata relating to any
    conceivable statistic in a separate database file
    that is spatially referenced within the map
  • Raster data encodes continuous data as pixel
    values for a range of remotely sensed information

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Suggested Reading
  • Mapping ways of representing the world by
    Dorling and Fairbairn, 1997
  • ESRI map book. Implementing concepts of
    Geography. Volume 14, 1999
  • Getting started with Geographical Information
    Systems by Clarke K., 1997

33
PRACTICAL Today
Groups A2, B1 B2 (2pm 330pm) A1, C1 C2
(330pm 5pm) Loxford L106
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