GISClase4 Eng
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Transcript of GISClase4 Eng
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Maps, scales andprojections
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Last class:
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Create a map
• Visualiza information using different tools
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Manage data frames
• Use graphic representation to realate various sourinformation
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In this class:
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Maps, projections and scales
• Change projection of a map
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Importance of coordinate system
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Map
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Graphic representation ofinformation
• Topographic terrain
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Subject
other info
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Map
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Create a map includes:
• Choose the information to be shown
• Simplify complex features
• Exagerate minute features
• Clasify in groups continuous information
• Use simbology in an accesible way
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Projections
• Project in 2D a quasi-sphere – the Earth
• Propertiess:
• Conformality preserve local angles. Thus preserves shape but areas imprecise.
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Area
maintains relaive size, but shape can be distorted
• Distance absolute distance between two points. No projection maiacross the world.
• Direction relative position between two points
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Projections
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Types:
• Cylindrical
• Conic
• Azimuth
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Projections
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Cylindric:Shape Area Direction D
Mercator Distorted towardsthe poles
conformal True across theworld
Ae
Robinson Small distorsion Small distorsion Very distorted C
la
Sinusoidal Distorted towardsthe equator
Constant Correct in theequator
Cth
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Mercator
Robins
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Projections
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ConicShape Area Direction D
Albers Constantarea
Accurate Accurate Accurate int heparalels
Aa
Conic
equidistant
Accurate Accurate Accurate
at small scales
A
s3
Lamberconformal
Conformal Minimumdistorsion
Accurate Aa
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Albers
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Projections
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AzimuthShape Area Direction D
Gnomonic Distorted atedges
Distorted atedges
Accurate fromthe center
D
Orthographic Distorted at
edges
Distorted at
edges
Accurate from
the center
A
fos
Stereographic Conformal Distorted atedges
Accurate fromthe center
De
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Gnomonic
Ortografica
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Scale
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Proportion between the real feature and the map
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Coordinate systems
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Relative position of a point form a reference one iplane
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Exercise
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Define map projections• Change coordinate systems
• Transformations