Transcript Unit I - Maps

Unit I - Maps
Cartography
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Cartography – science of mapmaking
Cartographers must choose:
• Types of projections
• Levels of simplification
• Levels of aggregation
• Map scale
• Symbols to use
Maps
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All maps are created by projecting
the earth’s 3D shape, which in
reality is a bumpy oblate spheroid or
geoid, onto a 2D surface.
3D shapes can never truly be 2D
All flat maps have some distortion in
their representation of distance,
shape, area, or direction.
Map Projections
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There are many possible map
projections.
A cartographer must choose the one
which will best represent their
purpose for the map.
No best projection – the one chosen
depends on the data they wish to
represent.
Mercator Projection
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Preserves compass direction, distorts the
area of landmasses relative to each other
(higher latitudes – larger in size)
Fuller Projection
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Maintains the accurate size and shape of
landmasses but completely rearranges
direction, so that the cardinal directions
no longer have any meaning
Robinson Projection
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Provides an aesthetically pleasing balance
(does not maintain accurate area, shape,
distance, or direction…but minimizes
errors)
Azimuthal Projection
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Either the North or South pole is at the
center of the map
Level of Simplification
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Refers to the level of detail included
What cartographers choose to
display on the map depends on the
overall purpose of the map and the
size of the area covered
Level of Aggregation
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Refers to the size of the unit under
investigation such as cities, counties,
states, or countries
Depends on the purpose of the map
Scale
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Refers to ratio
between the distance
on a map and the
actual distance on the
earth’s surface
Small-scale: the ratio
between map units
and ground units is
small (usually for
large areas)
Large-scale: cover
much smaller regions
Resolution
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Refers to a map’s smallest
discernable unit – smallest thing you
see on a map.
Map Categories
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2 categories:
• Reference maps:
work well for
locating and
navigating between
places.
• Thematic maps:
display one or more
variables across a
specific space.
Symbols
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Isoline (contour):
lines that represent
quantities of equal
value and are familiar
to those who use
topographic maps for
navigation – also used
to represent values
(population density).
Proportional symbols:
the size of the chosen
symbol – such as a
circle or triangle –
indicates the relative
magnitude of some
value for a given
geographic region.
Type of Maps
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Example of Dot Map
Location charts:
convey a large
amount of information
by associating charts
with specific mapped
locations.
Dot maps: use points
to show the precise
locations of specific
observations or
occurrences (crime,
births).
Type of Maps Cont.
Example of Choropleth Map
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Choropleth maps: use colors or tonal to represent
categories of data for given geographic areas.
Cartograms: transform space, such that the political unit –
a state, country, with the greatest value of some type of
data is represented by the largest relative area.
Visualizations
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Another interesting class of maps –
become increasingly popular in
recent years.
Use sophisticated software to create
dynamic computer maps, some of
which are 3-D or interactive.
Cognitive “Mental” Maps
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An individual’s internal, geographic
understanding of a place.
Formed when people perceive information
about their surroundings and then process
that information into a mental image that
reflects both the physical environment and
that individual’s social, cultural, and
psychological framework.
May include hazards – items/places a
person avoids during their daily routine.
Preference Maps
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Show people’s ideas about the
environmental, social, or economic
quality of life in various places.
Location/Distance
Geographers use these to establish location and
distance:
• Coordinate system
• Absolute location
• Longitude and
latitude
• Meridians – Prime
Meridian
• International Date
Line
• Parallels
• Site
• Situation – Relative
location
• Absolute distance
• Relative distance
• Connectivity
• Time-Space
Convergence