Transcript CARTOGRAPHIC BASICS - University of Arizona

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:
 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?
CARTOGRAPHIC BASICS
Where am I?
How far to my destination?
In what direction do I go?
How large?
What shape?
After James R. Smith, page 46
CARTOGRAPHIC BASICS
All maps have the same goal:

Communicating spatial relationships
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Communicating the ‘form’ of the landscape
Basic characteristics of all maps:
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Location
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Attribution
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Reduction of reality
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Scale
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Geometrical transformation/projection
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Abstractions of reality

Symbolism
CARTOGRAPHIC BASICS
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
CARTOGRAPHIC BASICS
Classification of maps:

Classed by Scale
Small scale
Medium scale
Large scale

Classed by Function
General reference maps
Thematic/special purpose maps
Charts

Classed by Subject Matter
Cadastral maps
Plans
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.
CARTOGRAPHIC BASICS
Mapping involves information transformations:

Data collection

Selection

Classification
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Simplification
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Exaggeration

Symbolization
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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?
CARTOGRAPHIC BASICS
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.
HISTORY OF CARTOGRAPHY
Changing ideas about cartography:

Earliest maps are figurative, ceremonial, artistic
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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
HISTORY OF CARTOGRAPHY
100 A.D. – geometry
1200 – Dark Ages
1300 – Renaissance
1680 – Enlightenment
1800s – Place => Space
1950+ -- Systems Approach
From Robinson, Sixth Edition, page 22
HISTORY OF CARTOGRAPHY
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:
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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.
HISTORY OF CARTOGRAPHY
Magnetic Compass
Mechanical Printing Press
Lens Grinding, Telescope Lenses, Lasers
Photography, Lithography
Computer Technology
BASIC GEODESY
“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.”
BASIC GEODESY
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
continents.
BASIC GEODESY
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
BASIC GEODESY
From James R. Smith, page 34
BASIC GEODESY
After James R. Smith, page 52
BASIC GEODESY
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