Map Map ProjectionsProjections

Map ProjectionsMap ProjectionsPutting a sphere on a flat surface messes up

certain realities:‐ Distance‐ Direction‐ Shape‐ Area

Each map keeps one or two things true (pros), but the others are not accurate (cons).

MercatorMercator

Pros:Direction

Cons:ShapeDistanceArea

Africa is actually 14 times larger than Greenland!

RobinsonRobinsonPros: Cons:Better area Direction

and shape Distance

Goode homolosineGoode homolosine

Pros:ShapeArea

Cons:DirectionDistance

Latitude and Longitude

Hemispheres

Hemispheres

The Earth’s GridAny spot on Earth can be plotted with latitude

and longitude.• Lines of latitude run east-west

– “Lateral” means “side-to-side” (lateral pass)– Also called parallels

• Measured in degrees of N or S

• 0° latitude is the Equator

• 90° N is the North Pole

• 90° S is the South Pole

LatitudeLatitude

Equator

Measu

re North

Measu

re South

Upper Latitudes

Lower Latitudes

LongitudeLongitude

• Lines of longitude run north-south– “All lines of longitude are long”– Also called meridians

• Measured in degrees of E or W

• 0° longitude is the Prime Meridian– Runs through Greenwich, England, just outside

London

• 180° E/W is the International Date Line

LongitudeLongitude0°

180° W 180° E

Measure EastMeasure WestP

rime M

eridian

34º N

35º N

18º E 19º E

34º 5’ N

18º 25’ E

The Earth’s Grid• A specific location uses N or S and W or E

for each coordinate pair

• Three ways to show coordinates:– Degrees, minutes, seconds:

30°, 15’, 45” N; 54°, 20’, 10” W• 1 degree = 60 minutes; 1 minute = 60 seconds

**Note: This is not in reference to time!

– Deg:min:sec : 30:15:45N, 54:20:10W

Three ways to show coordinates continued:

30:15:45N, 54:20:10W =– Decimals: 30.2625, -54. 336111

** (south and west are negative numbers)

• Found by dividing minutes/60 – i.e. 15 minutes = 15/60 = .25

• And then seconds/3600– i.e. 45 seconds = 45/3600 = .0125

• Add the two together: – .25 + .0125 = .2625

Latitude and LongitudeTogether, any point on Earth can be plotted on

a map

Use both coordinates together:

• Latitude, longitude40° N, 85° E 10° S, 15° W

• Walton: 33:59:20.663 N, 84:26:30.718 W

– This is the Front Office

Why Degrees, Minutes, Seconds?

• A circle is 360°– When computing various

angles, we base our measurements on degrees.

• i.e. Right angles are 90 °• An angle between 90° and

91° require requires minutes and seconds to find the specific angle.

• In 3D, we add the Z Axis, – which requires the

second degree measurement