The Map as a Model of Geographic Data

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The Map as a Model of Geographic Data

• The Language of Spatial Thinking
• Doç.Dr. Necla ULUGTEKIN
• ITÜ

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Spatial thinking requires us to be able to
select observe measure catalogue
characterise what we encounter.
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Data are collected

• in the field ? basic (absolute) data
• remote sensing ? basic (absolute) data
• existing maps ? derived data
• catalogues ? derived data
• ...

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A knowledge about cartographic methods will
increase a portion of our spatial vocabulary that
we have called graphicacy.

• Existing maps into the GIS
• Different level of generalisation
• Different level of scales
• Different projections
• Different symbolisation

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Cartography is the art, science and technology of
making maps together with their study as
scientific documents and works of art. (1973,
ICA)
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Cartography is the organisation, presentation,
communication and utilisation of geo-information
in graphic, digital or tactile form.(ICA, 1991)
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Map

• an abstraction of reality, it is not reality
  itself.
• the fundamental language of geography.
• symbolise image of geographical reality
• representing selected feature
• representing feature relationships
• representing characteristics

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Maps can be used

• Navigation
• Exploration
• Discovery
• Interactive computer navigation
• Education
• Forecasting

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Primary Types of Maps

• Topographic Map (General Reference)
• Thematic Map

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GIS works together

• geology
• surveying
• soil science
• other disciplines

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GIS is used in these disciplines,in addition to

• Geological maps
• Topographic maps
• Cadastral Maps
• Soil Maps

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The thematic context of GIS includes

• Vegetation maps
• Transportation maps
• Animal distribution maps
• Utility maps
• Urban plans
• Zoning maps
• ...

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GIS is

• hardware
• software
• people (organisation)
• data

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GIS is about

• data integration
• spatial analysis
• link with application based models

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The traditional approach to mapping called the
communication paradigm

• The map was a final product designed to
  communicate a spatial pattern through the use of
  symbols, class limit selection and so on.

The traditional method was limited because raw,
pre-classified data are not readily available to
the map user
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Communication Paradigm
Real World
Cartographer Conception
Map
Map User Conceptions
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The alternative approach to cartography which is
computer technology called the analytical or
holistic paradigm

• Maintains the raw attribute data inside a
  computer storage device and display data based on
  user needs and user classifications

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Map Scale

• Scale is the ratio of distance on the map to the
  same distance as appears on the earth
• Methods of illustrating map scale
• verbal scale 1mm 1000 mm
• representation fraction 11000
• graphic or bar scale
• 11000 ? 15000 ? 110 000 ? 125 000

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Generalisation

• Every map is, in principle, generalised.
• Why?
• increasing density of the map contents due to
  scale reduction
• limit of sharpness of the eye, printing
  capabilities
• minimum sizes
• the choice of degree of generalisation depends on
  aim and scale of the map.

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Map Characteristics

• Maps as images of the world, represent the
  locations of objects, as well as their qualities
  or magnitudes.
• Objects are represented as points, line, areas or
  surfaces in the computer memory as like in the
  reality.

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Objects
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Levels of data measurements

• qualitative or nominal level
• ordered or ordinal level
• quantitative or interval level

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• GRID SYSTEMS for MAPPING
• Geographical Coordinates based on latitude and
  longitude for the locating of objects or features
  on the spherical earth or its reference globe.
• Rectangular Coordinates or Plane Coordinates
  allows us to locate objects correctly on these
  flat maps.

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Map Projection

• The three-dimensional geographic relationships of
  the Earth surface must be transformed to the
  two-dimensional plane of the map by any of
  several procedures called map projections.
• Division of map projections according to their
  properties
• conform projections
• equivalent (Equal-Area) projections
• equidistant projection
• others

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• Division of map projections according to their
  construction
• cylindrical projections
• conic projections
• azimuthal projections
• Division of map projections according to their
  aspect
• Polar (regular)
• Equatorial (transversal)
• oblique

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UNIVERSAL TRANSVERSE MERCATOR PROJECTION (UTM)

• cylindrical, equatorial, conform projection
• the area is covered by 80 South - 84 North
  latitude
• the earth is divided into 60 zones (each 6
  longitude)
• 180 West Longitude - 0 - 180 East Longitude
• 20 latitudinal belts (each 8 latitude)
• scale factor 0.9996
• origin shifted 500 000 m to east (false easting)
• origin shifted 10 000 000 m to south for the
  southern hemisphere

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• Projection surfaces

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The Cartographic Process

• data collection (first step of GIS)
• data compilation (classification and symbolism)
• map production
• map reproduction (output of GIS)

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Map symbolism

• According to their dimensional characteristics
• point symbol (location and identity)
• line symbol (linear characteristics)
• area symbol (provinces, countries, soil units)

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Map symbolism

• According to their shape cartographic symbol
  grouped in three main categories
• pictorial or descriptive symbols
• geometric or abstract symbols
• letter or number symbols
• other symbols (pie graph, bar graph etc.)

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Thematic Maps

• dot map is a proportional changing in data
• choropleth map (value-by-area mapping)
• statistical mapping
• class interval selection
• equal class or constant interval methods
• variable intervals - arithmetic, logarithmic,
  other mathematical series, unsystematic
  (contour line on a topographic map class interval
  selection for choropleth maps.)

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The Nature of Spatial Data

• model construction and geographic object
  selection (surveying, photogrammetry, remote
  sensing, recycling old maps, statistical surveys)
• select and construct cartographic representation
  (road map, topographic map, ...)
• medium output (paper map or on-screen map)
• Reality ? digital landscape model ? digital
  cartographic model ? map ? mental map

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What we learnt

• new perspective (map, scale, communication, ...)
• new concepts (cartography, generalisation,
  projection, ...)
• new people