The Map as a Model of
Geographic Data
The Language of Spatial Thinking
Doç.Dr. Necla ULUĞTEKİN
İTÜ
Spatial thinking requires us to be able to
select
observe
measure
catalogue
characterise
what we encounter.
Data are collected
•in the field
•remote sensing
•existing maps
•catalogues
• ...
 basic (absolute) data
 basic (absolute) data
 derived data
 derived data
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
Cartography is the art, science and
technology of making maps
together with their study
as scientific documents
and works of art.
(1973, ICA)
Cartography is the organisation,
presentation, communication and
utilisation of geo-information in
graphic, digital or tactile form.
(ICA, 1991)
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
Maps can be used
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Navigation
Exploration
Discovery
Interactive computer navigation
Education
Forecasting
…
Primary Types of Maps
• Topographic Map (General Reference)
• Thematic Map
GIS works together
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geology
surveying
soil science
other disciplines
GIS is used in these disciplines,
in addition to
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Geological maps
Topographic maps
Cadastral Maps
Soil Maps
The thematic context of GIS
includes
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Vegetation maps
Transportation maps
Animal distribution maps
Utility maps
Urban plans
Zoning maps
...
GIS is
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hardware
software
people (organisation)
data
GIS is about
• data integration
• spatial analysis
• link with application based models
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
Communication Paradigm
Real World
Cartographer
Conception
Map
Map User
Conceptions
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
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
1:1000
– graphic or bar scale
• 1:1000  1:5000  1:10 000  1:25 000
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.
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.
Objects
Entities
Attributes
Geometric
Data
house
owner
coordinates
parcel
use
coordinates
Levels of data measurements
• qualitative or nominal level
• ordered or ordinal level
• quantitative or interval level
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.
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
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conform projections
equivalent (Equal-Area) projections
equidistant projection
others
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
UNIVERSAL TRANSVERSE MERCATOR
PROJECTION (UTM)
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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
Projection surfaces
The Cartographic Process
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data collection (first step of GIS)
data compilation (classification and symbolism)
map production
map reproduction (output of GIS)
Map symbolism
• According to their dimensional
characteristics
– point symbol (location and identity)
– line symbol (linear characteristics)
– area symbol (provinces, countries, soil units)
Map symbolism
• According to their shape cartographic
symbol grouped in three main categories
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pictorial or descriptive symbols
geometric or abstract symbols
letter or number symbols
other symbols (pie graph, bar graph etc.)
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.)
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)
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Reality  digital landscape model  digital cartographic model  map  mental
map
What we learnt
• new perspective (map, scale, communication, ...)
• new concepts (cartography, generalisation,
projection, ...)
• new people