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CARTOGRAPHIC BASICS - PowerPoint PPT Presentation

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GIS IS NOT CARTOGRAPHY. CARTOGRAPHIC BASICS. Maps perform two important functions: Storage medium for information that humanity needs Provides a picture of the world to help understand spatial patterns, relationships, and environmental complexity Maps tell us:

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  • Maps perform two important functions:

  • Storage medium for information that humanity needs

  • Provides a picture of the world to help understand spatial

    patterns, relationships, and environmental complexity

    Maps tell us:

  • Where is it?

  • What is it?

  • (often) When is it?

  • What is nearby? How far away? In which direction? How

    do I get there?

  • What other things are there also?

  • How might they be related?

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Where am I? After James R. Smith, page 46

How far to my destination?

In what direction do I go?

How large?

What shape?

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  • All maps have the same goal:

  • Communicating spatial relationships

  • Communicating the ‘form’ of the landscape

    Basic characteristics of all maps:

  • Location

  • Attribution

  • Reduction of reality

  • Scale

  • Geometrical transformation/projection

  • Abstractions of reality

  • Symbolism

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  • Location and Attribution allow many types of relationships

  • to be formed:

  • Relationships among locations with no attributes –

    distance, bearing

  • Relationship among various attributes at the same point

  • Relationship among different locations of the same attribute

  • Relationships among locations of combined/derived

    attributes of given distributions -- spatial distribution

    of per capita income vs. educational attainment

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  • Classification of maps:

  • Classed by Scale

    Small scale

    Medium scale

    Large scale

  • Classed by Function

    General reference maps

    Thematic/special purpose maps


  • Classed by Subject Matter

    Cadastral maps


    Soil, vegetation, precipitation, etc.

    The principal task of cartography is to communicate

    environmental information. The task of the map designer is to enhance the map user's ability to retrieve information.

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  • Mapping involves information transformations:

  • Data collection

  • Selection

  • Classification

  • Simplification

  • Exaggeration

  • Symbolization

  • Use of map

    The cartographer's task - explore the ramifications of each

    mapping possibility and choose the most appropriate for the

    intended task. Who is your audience?

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Four main cartographic processes:

  • Collecting and selecting data for mapping

  • Manipulating and generalizing the data, designing and

    constructing the map

  • Reading or viewing the map

  • Interpreting the information presented on the map

    Skilled cartographers must be familiar with all mapping activities, including geodesy, surveying, photogrammetry, remote sensing, GIS.

    Skilled cartographers must be familiar with the principals of human thought and communication.

    Skilled cartographers must be familiar with the disciplines associated with the environmental features being mapped.

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  • Changing ideas about cartography:

  • Earliest maps are figurative, ceremonial, artistic

  • 100 A.D. – the Greeks develop concepts of geometry

  • 1200 A.D. - 'church maps' of the Dark Ages

  • 1300 A.D. - Renaissance brings major expansion of world

    knowledge, travel

  • 1680 AD – the Enlightenment – concept of 'Western science'

    and concern with positional accuracy

  • 1800s – place => space; concept of distribution; thematic maps

    come into being; environmental data becomes important

  • 1950+ - systems approach to the environment => reintegration

    of themes and concept of cartographic modeling

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100 A.D. – geometry

1200 – Dark Ages

1300 – Renaissance

1680 – Enlightenment

1800s – Place => Space

1950+ -- Systems Approach

From Robinson, Sixth Edition, page 22

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Constant goal:

Society demands maps that are timely, accurate and complete. There has been a continual demand for greater accessibility to lower cost maps. Cartographers' constant struggle with these demands leads to evolution of maps

Changing technology:

  • Manual techniques are still used today

  • 12th century – magnetic compass

  • 16th century – mechanical printing press

  • 17th century – optical technology

  • 19th century – photo-chemical technology

  • 1950 – electronic/computer technology

    The success of computer-assisted mapping rests on the skill of the cartographer and development/ application of computer system components within a cartographic environment.

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Magnetic Compass

Mechanical Printing Press

Lens Grinding, Telescope Lenses, Lasers

Photography, Lithography

Computer Technology

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“Geodesy is the science that determines the figure of the

earth and the interrelation of selected points on its surface

by either direct or indirect techniques.”

“Mapping involves determining the geographic locations

of features on the earth, transforming these locations into

positions on a flat map through the use of map projection,

and graphically symbolizing these features.”

“Cursed be he who moves his neighbor’s boundary stone.”

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  • The earth is not round:

  • Authalic sphere – a sphere with the same surface area as

    the ellipsoid – used as base figure for mapping.

  • WGS 72 and 84 ellipsoids based on satellite orbital data

  • Clarke 1866 ellipsoid used for mapping in North America

    (based on ground measurements made in Europe, India,

    Peru, Russia, South Africa)

  • Geoid is a more faithful figure of the earth – 3D shape

    approximated by mean sea level in the oceans and the

    surface of a series of sea-level canals crisscrossing the


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Cartographic use of sphere, ellipsoid, geoid:

  • Authalic sphere used for small scale maps of countries,

    continents, larger areas

  • Ellipsoid used for large scale maps such as topographic

    maps and nautical charts; GPS systems use ellipsoid

  • Geoid used as reference surface for ground surveyed

    horizontal and vertical positions; elevations determined

    relative to mean sea level geoid

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From James R. Smith, page 34

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After James R. Smith, page 52

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  • Direction on the earth:

  • Geographic/true directions determined by the orientation of

    the graticule on the earths' surface

  • Magnetic directions must take into account the compass

    variation/magnetic declination

  • True azimuth – clockwise angle a great circle makes with the

    meridan at point of origin (changes constantly along the arc)

    great circles = shortest distance between points

  • Constant azimuth – line which makes a fixed angle with all

    meridians (rhumb line or loxodrome); spirals to pole