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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

•

 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

•

 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