Models of the Earth

Latitude

• Also called parallelsAlso called parallels

• Measured in degrees north or southMeasured in degrees north or south

• Equator is the invisible line that divides the earth into Equator is the invisible line that divides the earth into the Northern and Southern hemispherethe Northern and Southern hemisphere

• Poles are 90º North and SouthPoles are 90º North and South

• Each degree is divided into 60 minutes and each Each degree is divided into 60 minutes and each minute is divided 60 seconds.minute is divided 60 seconds.

• Each minute is 1.85km.Each minute is 1.85km.

Latitude and Polaris

Aim: What is the relationship

between latitude and Polaris?

Polaris

• Also called the North Star (brightest).

• Always in the northern nighttime sky.

• Is located very close to the North Celestial Pole.

* Polaris *•Polaris' altitude, or height

above the horizon, is equal to an observer's latitude.

• As you move north and your latitude increases, Polaris' altitude also increases.

• But if you pass south of the equator, the North Star will no longer be visible and you'll need to check a map to find your latitude!

Longitude• Called meridiansCalled meridians• Measured in degrees East and WestMeasured in degrees East and West• Prime meridian is invisible line that passes through Prime meridian is invisible line that passes through

Greenwich, England and near the International Date line Greenwich, England and near the International Date line on the opposite side of the Earthon the opposite side of the Earth

• Lines run between 0º to 180º East and West.Lines run between 0º to 180º East and West.• Each degree can be divided into 60 minutes and each Each degree can be divided into 60 minutes and each

minute is divided into 60 seconds.minute is divided into 60 seconds.• Each degree equals 111 km at the equator and Each degree equals 111 km at the equator and

eventually goes to zero at the poles.eventually goes to zero at the poles.

Difference between geomagnetic and geographic poles

The angle between The angle between the geomagnetic and the geomagnetic and the geographic the geographic poles is called poles is called magnetic declinationmagnetic declination..

GPS

• Uses signals from 3 different satellites (of a total of 24) to determine location

Mapping the Earth’s Surface

• Cartographers are map makers

• Data is gathered from field surveys to remote sensing

• Globes are the best because flat maps distort areas of the Earth.

Technological Advances in Map Making• Air photos and satellite images relate to

actual 3-D landforms

• Satellite technology gives an even broader view of Earth by gathering data from broad areas of Earth’s surface.

Cylindrical or Mercator Projection

• Has a perfect grid systemHas a perfect grid system

• Distorts areas near the polesDistorts areas near the poles

• Good for small area mapsGood for small area maps

Azimuthal or Gnomonic Projections

• Made by placing a piece of paper on a globeMade by placing a piece of paper on a globe

• Little distortion at the point of contact but Little distortion at the point of contact but increases as you move from that pointincreases as you move from that point

• Used by navigatorsUsed by navigators

Conic Projections

• Made by placing a cone over a globeMade by placing a cone over a globe

• Areas near poles have least distortionAreas near poles have least distortion

• Small area maps are the bestSmall area maps are the best

Reading a Map

• Direction found on compassDirection found on compass

• Use the symbols in a legendUse the symbols in a legend

• Map scales for distance on the map verses Map scales for distance on the map verses the actual distancethe actual distance

Topographical Maps

• Show the surface features or topography of Show the surface features or topography of the landthe land

• Contours lines are used to show elevationContours lines are used to show elevation

• Contour interval is the distance between Contour interval is the distance between each lineeach line

• Index contour are bolded lines that give the Index contour are bolded lines that give the elevationelevation

7.5 minute quadrangle topographic map1:24,000-scale

• Lines close together indicates steep terrainLines close together indicates steep terrain

• Lines far apart indicates gradual changeLines far apart indicates gradual change

• V shape indicates valleys with a river V shape indicates valleys with a river flowing toward the open end of the Vflowing toward the open end of the V

• Depressions are indicated by hachured linesDepressions are indicated by hachured lines

Drawing Topographical Maps

Gradient• = Drop in elevation between 2 points

Distance between two points

• 20 = 4 m/km

5

1. What is the contour interval for this map?2. What is the distance between points E and F?3. What direction does Cedar River flow?4. What is the gradient between points D and E?5. Which side of hill C has the steepest slope?6. What is the elevation of the last depression line on hill B?

Now the Fun begins…read this map and tell me