Chapter 2: Mapping Our World

Latitude and LongitudeTypes of Maps

Remote Sensing

Latitude and LongitudeThe science of mapmaking is called cartography

Use an imaginary grid of parallel lines and vertical lines to locate points on Earth exactly

The grid line halfway between the north and south poles is called the equator, which separates Earth into two equal halves called the Northern Hemisphere and the Southern Hemisphere

LatitudeLines of latitude run parallel to the equator

Latitude – the distance in degrees north or south of the equator

The equator = 0°

North Pole = 90° N

South Pole = 90° S

LongitudeLongitude is the distance in degrees east or

west of the prime meridian

The prime meridian represents 0° longitude which goes through Greenwich, England

Points are numbered 0°-180° West if west of the prime meridian and 0° - 180° East if east of the prime meridian

Lines aren’t in parallel to measure longitude, they are in semicircles from pole to pole

Time ZonesEarth is divided into 24 time zones

Time is always changing because the Earth is ALWAYS spinning

Each time zone is 15°, roughly corresponding to lines of longitude

There are 6 different time zones in the United States

Alaska Standard Time, Hawaii-Aleutian Standard Time, Pacific, Mountain, Central, Eastern

Calendar DatesEach time you travel through a time zone, you

gain/lose time until, at some point, you gain/lose an entire day

The 180° Prime Meridian is also called the International Date Line, which serves as the transition line for calendar days

If you were going west across the line, you would add one day

If you were going east across the line, you would lose a day

Types of MapsMercator Projections

Conic Projections

Gnomonic Projections

Topographic Maps

Mercator ProjectionsA map that has

parallel lines of latitude and longitude

Landmasses at the poles are exaggeratedShapes of landmasses are correct, but their areas are distorted ex. Greenland and Australia

Used for plane and ship navigation

Conic ProjectionsMade by projecting

points and lines from a globe onto a cone

Used to make road maps and weather maps

Highly accurate for small areas

Distortion near the top and bottom

Gnomonic ProjectionsMade by projecting points and lines from a globe

onto a piece of paper that touches the globe at a single point

These projections distort direction and distance between landmasses

Used in plotting long-distance trips by air and by sea

Great circles – parallels are shown as circles around the pole

Only show one hemisphere at a time w/ distortion near the equator

Gnomonic Projections

Topographic MapsTopographic maps show changes in elevation of

Earth’s surface

Detailed maps showing the hills and valleys of an area, also show mountains, rivers, forests, bridges, etc.

Use lines, symbols, colors to represent changes in elevation and features on Earth’s surface

Topographic Maps

Topographic MapsContour Intervals – the space between side-by-

side contour lines that shows difference in elevations

Index Contours – Numbers that represent elevations on contour lines

Depression Contour Lines – Represent features with lower elevations than their surroundings, like craters and minesHachures – short lines at right angles to the contour line to indicate depressions (Figure 2-10 in your book)

point toward lower elevations

Map LegendsMap legends

explain what the symbols on maps represent

Map ScaleThe ratio between distances on a map and

actual distances on the surface of Earth

- Verbal scales – express distance as a statement- Ex. “one centimeter is equal to one kilometer”

- Graphic scales – consists of a line that represents a certain distance

- Fractional scales – expresses distance as a ratio - Ex. 1:63 500 - One centimeter on the map would

be equivalent to 63 500 cm on Earth’s surface

Remote Sensing

Remote sensing is the process of collecting data about Earth from far above Earth’s surface

Satellites gather information about Earth’s surface

The Electromagnetic Spectrum

The electromagnetic spectrum is the arrangement of electromagnetic radiation according to wavelengths

Satellites detect different wavelengths of energy reflected from Earth’s surface

All electromagnetic waves travel at the speed of light (300,000 km/s)

Different waves can be described according to wavelength and/or frequencyFrequency – the number of waves that pass a particular point each second

The Electromagnetic Spectrum

Landsat SatellitesReceives reflected wavelengths of energy

emitted by Earth’s surface

Features on Earth’s surface radiate warmth at different frequencies, so they show up different in images from satellites

Landsat satellites have a moving mirror with rows of detectors that measure energy when it scans the surface of the Earth

Landsat data used to study movements of Earth’s plates, rivers, earthquakes, pollution

Topex/Poseidon SatelliteUse radar to map features on the ocean floor by

using high-frequency signals transmitted from the satellite to the ocean surface

The returning echo is reflected off the water

Used to study tidal changes and global ocean currents

Global Positioning SystemGPS is a radio-navigation system of many

satellites that allow users to determine their exact position on Earth

The satellites orbit Earth and transmit microwaves with info. about the satellites position

Receivers calculate the users precise latitude and longitude by processing the signals emitted by the satellites

Sea BeamUsed to map the ocean floor

Located on a ship which uses sonar (sound waves) to detect and measure objects underwater

Sound waves are sent from the ship to the ocean floor and an echo is returned after bouncing off the seafloor

Computers calculate the distance to the bottom