The Map as a Model of Geographic Data

The Language of Spatial Thinking

Fundamentals of GIS

Michael N. DEMERS

Assoc.Prof.Dr. Necla ULUGTEKINulugtek@itu.edu.tr

Spatial thinking requires us to be able to

select observe measure catalogue

characterise what we encounter.

Data are collected

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

Scanning

The Digitizing Tablet

• 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)

A knowledge about cartographic methods will increase a portion of our spatial vocabulary that

we have called graphicacy.

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

• Navigation

• Exploration

• Discovery

• Interactive computer navigation

• Education

• Forecasting

• …

Primary Types of Maps• Topographic Map (General Reference)

• Thematic Map

GIS works together

• geology

• surveying

• soil science

• other disciplines...

GIS is used in these disciplines,in addition to

• Geological maps

• Topographic maps

• Cadastral Maps

• Soil Maps

The thematic context of GIS includes

• Vegetation maps

• Transportation maps

• Animal distribution maps

• Utility maps

• Urban plans

• Zoning maps

• ...

GIS is

• 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 paradigmThe 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 CartographerConception

Map

Map UserConceptions

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

• 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

Map Scale

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 size of symbols on map

• the choice of degree of generalisation depends on aim and scale of the map.

1:50 000

1:25 000

1 : 5 000

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

Parcel area (value)

Parcel owner (text)

photo

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 (elipsoidal) earth or its reference globe.

•Rectangular Coordinates or Plane Coordinates allows us to locate objects correctly on these flat maps.

elevationelevation

Sea level

GeographGeographiical Coordcal Coordiinatesnates

Parallel

Equator

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Pri

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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

Division of map projections according to their construction

• cylindrical projections

• conic projections

• azimuthal projectionsDivision of map projections according to their

aspect• Polar (regular)• Equatorial (transversal)• oblique

Projection surfaces

Perspective projection ! Pseudo Projections

a tangent conic (cylindirical or azimuthal) projection

with one standard parallel

a secant conic projection with two standard parallels

Position of the (earth) rotation axis to surface normal

• polar or regular I

• equatorial or transverse ___

• oblique /

• preserve the property of local shape

conformed projections

Lambert Conformal Conic

Mercator Projection

Perspective projection !

preserves distances but only along one or a few lines equidistant projections

the azimuthal equidistant projections

preserve the property of areaequal area or equivalent projections

Albers Equal Area

miscellaneous projections(pseudo ! )

Goodes Homolosine

Sinusoidal Projection

Robinson Projection

Winkel Tripel Projeksiyonu

MARS 2001

Winkel Tripel Projeksiyonu

a: original

b: equal area projection

c: conform projection

Arabian Island & Greenland

UTM (Universal Transverse Mercator) C.S.North

northern hemisphere

Central meridian for zone

500 000m E

Equator (0m N, 10 000 000m S)

southern hemisphereSouth .

? Prime meridian

1800W-1800E (60of longitude wide- 60 gores (zone)) 800S - 840N (80of latitude wide - 20 latitudinal belts)

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

• the Hayford ellipsoid, the ED50 datum

The Cartographic Process

• 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– pictorial or descriptive symbols– geometric or abstract symbols– letter or number symbols– other symbols (pie graph, bar graph etc.)

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visual variables

shape orientationsize

texture color value

Symbols

Color for map design

hue

saturation

intensity/value

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.)

0 100 km0M EDITE RRA NE AN SE A

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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)

realitydigital landscape model

digital cartographic modelmap

mental map (reality????)

What we learnt

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

projection, ...)

and• What we know? “new people”• ...