GEOG 370: Lec5&6
19 Cards in this Set
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Compromise Projections
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No areas of high or low distortion --> medium distortion all over the map
Only good for showing the whole earth, or almost all of it. Not good for smaller areas because distortion can be minimized at a smaller scale
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Tissot's Indicatrix
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Tool for visualizing distortion
How circles distort indicates the degree of distortion at certain areas
Circles w/ same area plotted visually on map to show distortion
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Direction - Loxodrome
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A line of constant compass direction; head one direction constantly
"Rhumb lines," not every map shows loxodromes as straight lines.
Mercator was invented to show loxodromes as straight lines (good for 16th cent. navigation)
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Direction - Great Circle
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Any line that can split the earth evenly in half
Equator is only parallel that is a great circle
There are an infinite number of great circles on earth.
A Great Circle is the shortest distance between two points
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Direction - Azimuthal Projections
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Planar projections, preserve straight lines out of the tangent point
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Projection Interruptions
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Any projection can be interrupted
Tears in map allow for minimizing of distortion
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Orthographic Projection
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Earth from space projection
Reminds people we live on earth
Doesn't preserve area, preserves great circles
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Map Elements - Mapped Area
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The area being mapped...duh
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Map Elements - Titles
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Title indicates what info is on the map, what it's about
Don't always need a title, depends on context
Title should say Where map is, Time Period (when) and What (what's being projected. Things become outdated)
Title can be catchy and eye grabbing, use subtitles to be more information…
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Map Elements - Legend
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Identifies what the representation means
Usually need a title/header/explanatory text
Units are important
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Map Elements - Metadata
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3 important things in Metadata:
-Name: Take responsibility for your work
-Source: Where data came from is important so ppl can check your work and give credit to whoever collected the data
-Projection Information: useful for others to know how features are changed and represented
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Map Elements - Scale
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Ratio btwn earth and the map
Scale is not constant, not true for most of the map.
Put scale to represent the most accurate distance
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Scale - Representative Fraction
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e.g. 1 : 125,000
Good at telling how big the earth is compared to the map, scale bar doesnt do that
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Scale - Verbal Scale
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Says in a phrase "one unit is equal to one of another unit"
e.g. One inch equals one mile
Uses imaginative mind descriptions
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Scale - Scale Bar
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Shows people the scale instead of telling them, it is graphical
Can take measurements, easy way to figure distances
Advantage: Scale bar changes as map size changes, and the other options are fixed
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Orientation Device
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Tells which way is which
Can use the graticule for orientation
Don't always need an orientation device. If no north arrow, ppl will assume north is up. North isn't always straight up
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Neatline
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Border of the map, where map begins and ends.
Helps distinguish btwn map items
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Locator Map
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Other maps can be used as map elements
Locator Maps show the general location of the main map at a smaller scale than the main map
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Inset Map
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Larger scale than the main map
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GEOG 370: Lec7&8