Reading MapsReading Maps

Earth ScienceEarth Science

Mr. BimberMr. Bimber

Map Projections:Map Projections:

You can’t draw the round You can’t draw the round earth on flat paper, so all earth on flat paper, so all maps are distorted.maps are distorted.

Take a transparent globe Take a transparent globe with a light shining out with a light shining out from the center. Trace the from the center. Trace the outlines of the land on a outlines of the land on a piece of paper held piece of paper held against the globe. That’s against the globe. That’s a a map projectionmap projection..

Cylindrical ProjectionCylindrical Projection

A cylindrical projection: the map is traced on a cylinder.A cylindrical projection: the map is traced on a cylinder.Latitude and Longitude lines are always right angles.Latitude and Longitude lines are always right angles.– This is good for navigators and pilots.This is good for navigators and pilots.

The areas near the poles are larger, and distorted.The areas near the poles are larger, and distorted.– Mercator maps are cylindricalMercator maps are cylindrical

Azimuthal ProjectionsAzimuthal Projections

Azimuthal Projections are traced on flat paper.Azimuthal Projections are traced on flat paper.

Shape & direction are distorted near the edges.Shape & direction are distorted near the edges.

Examples: polar projection, gnomonic projection.Examples: polar projection, gnomonic projection.

Conic ProjectionsConic Projections

Conic projections are traced on paper rolled into a cone. Conic projections are traced on paper rolled into a cone.

They are distorted near the top and bottom, and latitude They are distorted near the top and bottom, and latitude lines are curved.lines are curved.

These have the least distortion for small area maps: These have the least distortion for small area maps: almost all road and state maps are conic projections.almost all road and state maps are conic projections.

Map ScaleMap Scale

A Map’s Scale lets you measure and compare A Map’s Scale lets you measure and compare map distances to distances in the real world.map distances to distances in the real world.The scale can be marked rulers, a ratio, or a The scale can be marked rulers, a ratio, or a fraction fraction – (This map scale as a fraction would be 1/250,000.)(This map scale as a fraction would be 1/250,000.)

Map Scales ComparedMap Scales Compared

Small scale maps Small scale maps show more of the show more of the world, but less world, but less detail.detail.

……

Large scale maps Large scale maps show less area, but show less area, but more detail.more detail.

Map Scales check:Map Scales check:

Which map shows the most land area? Which map shows the most land area? Which map shows the most detail? Which map shows the most detail? Is the map on the left smaller or larger scale?Is the map on the left smaller or larger scale?Two places three inches apart on the left map are how far apart in Two places three inches apart on the left map are how far apart in the real world? the real world?

LatitudeLatitude

Latitude lines Latitude lines run east and run east and west in circles west in circles all the way all the way around the around the earth.earth.They are They are measured in measured in degrees north degrees north or south of the or south of the equator.equator.

LongitudeLongitude

Go only half Go only half way around the way around the earth.earth.Lines run Lines run between north between north and south and south poles.poles.Lines are east Lines are east or west of the or west of the Prime Meridian.Prime Meridian.

Latitude and LongitudeLatitude and Longitude

You can locate any place on earth by giving its You can locate any place on earth by giving its Latitude north or south of the equator, and its Latitude north or south of the equator, and its Longitude east or west of the Prime Meridian.Longitude east or west of the Prime Meridian.

Degrees, minutes, secondsDegrees, minutes, seconds

To locate places To locate places more accurately, more accurately, each degree can each degree can be divided into sixty be divided into sixty arc minutes, and arc minutes, and each minute into each minute into sixty arc seconds.sixty arc seconds.