Geography Basics

The Earth

• Shape- oblate spheroid• Minor bulge at the equator• Insignificant on a standard globe

• Equatorial circumference– - 24,900 mi

Surface Topography

• Surface topography is not completely smooth– Highest point- Mt. Everest ~29,000 ft above sea

level

– Lowest point- Marianas Trench(Challenger Deep) ~ 36,200 ft below sea level

Grid System

• Latitude and longitude is the same as plotting points on a grid– Equator is the x “axis”– Prime meridian is the y “axis”– Every location has a set of coordinates• These coordinates are latitude and longitude

Latitude

• Lines of latitude are called parallels– They are evenly spaced and parallel

• They go from – 0-90 degrees N of the equator– 0-90 degrees S of the equator

Equator

• Runs horizontally around the Earth• 0 degrees latitude

Longitude

• Lines of longitude are called meridians– They are NOT parallel , but converge at the poles– Farthest apart at the equator

• They go from– 0-180 degrees East of the Prime Meridian– 0-180 degrees West of the Prime Meridian

Prime Meridian

• Runs vertically around the Earth• Originates in Greenwich, UK• 0 degrees longitude

Great Circles

• Great Circle is any imaginary circle whose plane passes through the center of the Earth.– Divides Earth into two equal hemispheres– All lines of longitude– Only one line of latitude

• equator

• Small circle– Does not divide the Earthinto equal halves

Great Circle

• Circle of Illumination– Divides Earth into night and day

Great Circle

• Shortest travel route– Airplanes follow the great circle

The Four Quadrants

•N- North of equator•S- South of equator•E- East of Prime

Meridian•W- West of Prime

Meridian

(N, W) (N, E)

(S, W) (S, E)

Point of Origin (0,0)?

•The origin point (0,0) is where the equator intersects the prime meridian.

North America

•All points in North America are

–North of equator–West of Prime Meridian

(N, W)

Prime Meridian

Australia?

•What would be the latitude and longitude directions in Australia?

Prime Meridian ?

If you said South and East , you’re right!

See If You Can Tell In Which Quarter These Lat/Longs Are Located

•1. 41°N, 21°E•2. 37°N, 76°W•3. 72°S,

141°W•4. 7°S, 23°W•5. 15°N, 29°E•6. 34°S, 151°E

A B

C D

BACCBD

Degrees, Minutes, Seconds

• This is a set of coordinates for New York City– 41°8 44″ N, 73°59 42″ W′ ′

– 41 degrees, 8 minutes, 44 seconds NORTH– 73 degrees, 59 minutes, 42 seconds WEST

Lat Long– 1 Degree = 60 minutes ~ 69 mi var.– 1 minutes = 60 seconds ~ 1.15 mi– 1 second ~102 ft

Degrees of an arc

• How many degrees are in a circle?

Equator

North Pole

30o

So, if you were standing on the spot where this line emerged from the center of the Earth you would be 30o above the equator.

Decimal Degrees

• Or measured in decimal degrees– More precise than degrees, minutes, seconds– More commonly used for GPS40.7142 , -74.0064 – New York City

– North/East = positive– South/West= negative

Time Zones

• Based on relationship between longitude, rotation, and time.

• Prime Meridian at Greenwich, UK• 24 time zones (1 for each hour of the day)– 15 degrees each hour

Time Zones

Time Zones

• Time for all locations based on GMT (Greenwich Mean Time)

• A location 120 degrees west of Greenwich would be 8 hours behind– 120°/15° = 8 hours

International Date Line

• Approx .180th meridian

• Traveling east- turn backa full day

• Traveling west- turn aheada full day

GPS

• Global positioning system– Triangulation from 3 (or more) satellite sources– Gives lat/long position

Maps and Projections

• Maps are distorted– Trying to project a spherical surface on flat paper

– Distortion is more evident for larger areas• i.e. easier to see distortion on a map of the world

Maps and Projections

Conic- mid latitudes

Planar/ Azimuthal- poles

Cylindrical- parallel meridians

Maps and Projections

• Mercator projection- – East-west distortion of high latitude areas

Maps and Projections

• 4 important properties– Parallels of latitude always parallel– Parallels are evenly spaced– Meridians of longitude converge at the poles– Meridians and parallels cross at right angles

– No map can maintain all 4 and be true

Map Basics

• Legend (symbol key)– Scale• Ground distance and distance on a map

– Verbal scale- 1 cm on map = 1 km on ground– RF (representative fraction) scale - 1:1000 – Graphic/bar scale

– Direction• Magnetic declination

Thematic Maps

• Discrete Maps– Data at a specific point

Thematic Maps

• Continuous Map– Measurable data everywhere

– Isolines- connect points with the same numerical value

Topographic Maps

• Contour lines- isolines that connect values in elevation

• Contour interval- value of each line– Closer lines together= steeper gradient

• Vertical exaggeration- stretch the height of a side profile to make contours more clear

Topographic Maps

GIS (Geographic Information Systems)

• Modern mapmaking/ computer software• Uses combinations of different thematic layers

to map information – Examples • Combine homes under 200,000 $ with locations of

schools• Combine locations of a type of factory with known

contaminated sites

GIS layers