MAP PROJECTIONS. What is a Map Projection? Properties of Map Projections Types of Map Projections.

MAP PROJECTIONSMAP PROJECTIONS

MAP PROJECTIONSMAP PROJECTIONS

What is a Map Projection?What is a Map Projection?Properties of Map Properties of Map ProjectionsProjectionsTypes of Map ProjectionsTypes of Map Projections

What is a Map Projection?What is a Map Projection?

• THE ONLY THE ONLY TRUE TRUE REPRESENTATION OF EARTH, FREE REPRESENTATION OF EARTH, FREE OF DISTORTION IS A OF DISTORTION IS A GLOBE.GLOBE.

• MAPS ARE FLATMAPS ARE FLAT• PROCESS BY WHICH GEOGRAPHIC LOCATIONS (LAT PROCESS BY WHICH GEOGRAPHIC LOCATIONS (LAT

& LONG) ARE TRANSFORMED FROM A 3 - & LONG) ARE TRANSFORMED FROM A 3 - DIMENSIONAL SPHERE TO A 2 - DIMENSIONAL FLAT DIMENSIONAL SPHERE TO A 2 - DIMENSIONAL FLAT MAP IS CALLED AMAP IS CALLED A PROJECTION PROJECTION

DistortionsDistortions

• EVERY MAP PROJECTION DISTORTS AT LEAST THREE, AND SOMETIMES ALL FOUR, OF THE FOLLOWING PROPERTIES:

SHAPEAREADISTANCEDIRECTION

Properties of ProjectionsProperties of Projections

The Cartographer decides on which The Cartographer decides on which projection to use depending on which projection to use depending on which properties of the earth are to be kept in properties of the earth are to be kept in the flat map. The following slides will the flat map. The following slides will give you a more detailed idea of these give you a more detailed idea of these properties which will help you select the properties which will help you select the best map for your particular purpose.best map for your particular purpose.

Properties of Map Properties of Map ProjectionsProjections

1.1. CONFORMAL: CONFORMAL: A CONFORMAL PROJECTION MAINTAINS SHAPE IN SMALL LOCALIZED AREAS

2.2. EQUAL AREAEQUAL AREA: THESE PROJECTIONS SHOW THE AREAS OF ALL REGIONS ON THE MAP IN THE SAME PROPORTION TO THEIR TRUE AREAS ON THE GLOBE.

3.3. EQUIDISTANTEQUIDISTANT: NO MAP CAN SHOW DISTANT CORRECTLY BETWEEN ALL POINTS ON A MAP, BUT ONLY FROM ONE, OR AT MOST TWO, POINTS TO ANY OTHER POINT. THIS PROJECTION MAINTAINS DISTANCE.

4.4. AZIMUTHALAZIMUTHAL:THIS PROJECTION CORRECTLY SHOWS DIRECTIONS (AZIMUTHS) FROM A SINGLE POINT TO ALL OTHER POINTS ON A MAP.

Types of Map ProjectionsTypes of Map Projections

Map projections are related to either a Map projections are related to either a cylinder, cone cylinder, cone or planeor plane. Imagine a transparent globe with a light in . Imagine a transparent globe with a light in the middle. You can project the globe onto a flat the middle. You can project the globe onto a flat sheet of paper just as a picture is projected on a sheet of paper just as a picture is projected on a screen. screen.

In this case, because the earth is round, the paper can In this case, because the earth is round, the paper can be rolled into a be rolled into a cylindercylinder, a , a conecone, or a , or a planeplane. . The projection is made, and the paper is unrolled to The projection is made, and the paper is unrolled to reveal your map! Even where you place the light reveal your map! Even where you place the light source to make the projection becomes an issue. Does source to make the projection becomes an issue. Does the light source go in the middle of the globe the light source go in the middle of the globe (Gnomonic), touching the globe (Stereographic) or off (Gnomonic), touching the globe (Stereographic) or off the globe altogether (Orthographic)? the globe altogether (Orthographic)? So, we have three basic types of map projections:So, we have three basic types of map projections:

1. Cylindrical 2. Conical 3. Planar1. Cylindrical 2. Conical 3. Planar

Cylindrical ProjectionsCylindrical Projections

Cylindrical Projections-The Cylindrical Projections-The Map Map

Cylindrical Projections-The Cylindrical Projections-The Map Map

Cylindrical Projections-The Cylindrical Projections-The Map Map

Conical ProjectionsConical Projections

Conical Projections – The Conical Projections – The MapMap

Notice: this projection preserves the shape or conformal property

Conical Projections – The Conical Projections – The MapMap

Notice: this projection preserves the distance property

Azimuthal ProjectionsAzimuthal Projections

Azimuthal Projections – The Azimuthal Projections – The Map Map

Azimuthal Projections – The Azimuthal Projections – The Map Map

Azimuthal Projections – The Azimuthal Projections – The Map Map

SummarySummary

• A Cartographer decides which map A Cartographer decides which map projection to use for his/her purposes.projection to use for his/her purposes.

• You chose your projection based on the You chose your projection based on the properties properties you want to preserve:you want to preserve:

equidistant – distance equidistant – distance preserved preserved conformal conformal – shape preserved– shape preserved equal area – area preservedequal area – area preserved azimuthal – directions are azimuthal – directions are preservedpreserved

SummarySummary

• You then decide on which You then decide on which type of type of projectionprojection you want. This depends on you want. This depends on which area of the earth you want to which area of the earth you want to display and how you want to display it:display and how you want to display it:

• Cylindrical – eg. MercatorCylindrical – eg. Mercator• Conical – eg. Lambert Conical – eg. Lambert • Planar – eg. Azimuthal Planar – eg. Azimuthal

• Each type of projection is associated with many Each type of projection is associated with many different projections that preserve different different projections that preserve different properties. They each get their own name.properties. They each get their own name.For example, there is a Lambert Conformal For example, there is a Lambert Conformal Conic AND a Lambert Equidistant ConicConic AND a Lambert Equidistant Conic

ReferencesReferences

• Most of the diagrams in this presentation were Most of the diagrams in this presentation were borrowed from the following website. borrowed from the following website.

•Dana, Peter H., “Map Projection Overview”, Dana, Peter H., “Map Projection Overview”, University University of Colorado Boulder. of Colorado Boulder. (October, 2000): (October, 2000): Online. Internet.  Online. Internet.  Available at Available at http://www.colorado.edu/geography/gcraft/notes/mapphttp://www.colorado.edu/geography/gcraft/notes/mapproj/mapproj.htmlroj/mapproj.html

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