Objectives• Compare and contrast latitude and longitude.

Latitude and Longitude

• Describe how time zones vary.

– cartography

– equator

– latitude

– longitude

– prime meridian

– International Date Line

Vocabulary

• Cartographers use an imaginary grid of parallel lines and vertical lines to locate points on Earth.

• The equator circles Earth halfway between the north and south poles separating Earth into two equal halves called the northern hemisphere and the southern hemisphere.

• Cartography is the science of mapmaking.

Latitude and Longitude• For thousands of years, people have used maps

to define borders and to find places.

Latitude and Longitude

Latitude• Lines of latitude are lines running parallel to

the equator.

Latitude and Longitude

• Latitude is the distance in degrees north or south of the equator.

Latitude• Latitude is thus measured from 0° at the equator

to 90° at the poles.

Latitude and Longitude

• Locations north of the equator are referred to by degrees north latitude (N).

• Locations south of the equator are referred to by degrees south latitude (S).

Latitude

Degrees of Latitude

Latitude and Longitude

– Each degree of latitude is equivalent to about 111 km on Earth’s surface.

– To locate positions on Earth more precisely, cartographers break down degrees of latitude into 60 smaller units, called minutes (´).

– A minute of latitude can be further divided into seconds (´´).

– Longitude is also divided into degrees, minutes, and seconds.

Longitude• To locate positions in east and west directions,

cartographers use lines of longitude, also known as meridians.

Latitude and Longitude

• Longitude is the distance in degrees east or west of the prime meridian.

• The prime meridian, representing 0° longitude, is the reference point for longitude.

Longitude• Points west of the prime meridian are numbered

from 0° to 180° west longitude (W).

Latitude and Longitude

• Points east of the prime meridian are numbered from 0° to 180° east longitude (E).

Longitude

Semicircles

Latitude and Longitude

– Lines of longitude are not parallel; they are large semicircles that extend vertically from pole to pole.

– The distances covered by degrees of longitude vary with location.

– One degree of longitude varies from about 111 km at the equator to essentially the distance covered by a point at the poles.

Degrees of Longitude

Longitude

Locating Places with Coordinates

Latitude and Longitude

– Both latitude and longitude are needed to precisely locate positions on Earth.

– For example, the location of New Orleans is 29°57´N, 90°04´W.

– Note that latitude comes first in reference to the coordinates of a particular location.

Time Zones• Because Earth takes about 24 hours to rotate

once on its axis, it is divided into 24 times zones, each representing a different hour.

Latitude and Longitude

Time Zones• Each time zone is 15° wide, corresponding

roughly to lines of longitude.

Latitude and Longitude

• Time zone boundaries have been adjusted in local areas for convenience.

Time Zones• There are six

different time zones in the United States.

Latitude and Longitude

Time Zones

Calendar Dates

Latitude and Longitude

– Every time zone experiences this transition from one day to the next, with the calendar advancing to the next day at midnight.

– Each time you travel through a time zone, you gain or lose time, eventually gaining or losing an entire day.

– The International Date Line, or 180° meridian, serves as the transition line for calendar days.

– Traveling west across the International Date Line, you would advance your calendar one day.

– Traveling east, you would move your calendar back one day.

Objectives• Compare and contrast different map projections.

• Analyze topographic maps.

• Describe map characteristics, such as map scales and map legends

– Mercator projection

– conic projection

– gnomonic projection

– topographic map

– contour line

– contour interval

– map legend

– map scale

Vocabulary

Types of Maps

Types of Maps• Maps are flat models of a three-dimensional

object, Earth.

Types of Maps

• All flat maps distort to some degree either the shapes or the areas of landmasses.

• Cartographers use projections to make maps.

• A map projection is made by transferring points and lines on a globe’s surface onto a sheet of paper.

Mercator Projections• A Mercator projection is a map that has

parallel lines of latitude and longitude.

Types of Maps

• In a Mercator projection, the shapes of the landmasses are correct, but their areas are distorted.

Conic Projections• A conic projection is a map made

by projecting points and lines from a globe onto a cone.

Types of Maps

• The cone touches the globe at a particular line of latitude along which there is very little distortion in the areas or shapes of landmasses.

• Distortion is evident near the top and bottom of the projection.

Gnomonic Projections• A gnomonic projection is a map made by

projecting points and lines from a globe onto a piece of paper that touches the globe at a single point.

Types of Maps

• Gnomonic projections distort direction and distance between landmasses.

• Gnomonic projections are useful in plotting long-distance trips by air or sea.

Gnomonic Projections• Great circles are imaginary lines that divide Earth

into two equal halves.

Types of Maps

• On a sphere such as Earth, the shortest distance between two points lies along a great circle.

• Navigators connect points on gnomonic projections to plot great-circle routes.

Topographic Maps• Topographic maps are

detailed maps showing the elevations of hills and valleys of an area.

Types of Maps

• Topographic maps use lines, symbols, and colors to represent changes in elevation and features on Earth’s surface.

Topographic Maps

Contour Lines

Types of Maps

– Elevation on a topographic map is represented by a contour line.

– A contour line connects points of equal elevation.

– Elevation refers to the distance of a location above or below sea level.

Topographic Maps

Contour Intervals

Types of Maps

– Topographic maps use contour lines to show changes in elevation.

– The contour interval is the difference in elevation between two side-by-side contour lines.

– The contour interval is dependent on the terrain.

Topographic Maps

Index Contours

Types of Maps

– Index contours are contour lines that are marked by numbers representing their elevations.

– If a contour interval on a map is 5 m, you can determine the elevations represented by other lines around the index contour by adding or subtracting 5 m from the elevation indicated on the index contour.

Topographic Maps

Depression Contour Lines

Types of Maps

– Depression contour lines are used to represent features that are lower than the surrounding area.

– On a map, depression contour lines have hachures, or short lines at right angles to the contour line that point toward the lower elevation, to indicate depressions.

• These features are represented by different symbols.

• A map legend explains what the symbols represent.

Map Legends• Topographic maps and most

other maps include both human-made and natural features that are located on Earth’s surface.

Types of Maps

• A map scale is the ratio between distances on a map and actual distances on the surface of Earth.

Map Scales• When using a map, you need to know how to

measure distances.

Types of Maps

Map Scales• There are three types of map scales: verbal

scales, graphic scales, and fractional scales.

Types of Maps

– A verbal scale expresses distance as a statement, such as “One centimeter is equal to one kilometer.”

– A graphic scale consists of a line that represents a certain distance, such as 5 km or 5 miles.

– A fractional scale expresses distance as a ratio, such as 1:63 500.

• remote sensing

• electromagnetic spectrum

• frequency

• Landsat satellite

Objectives• Compare and contrast the different forms of

radiation in the electromagnetic spectrum.

• Discuss how satellites and sonar are used to map Earth’s surface and its oceans.

• Describe the Global Positioning System.

Vocabulary

Remote Sensing

• Topex/Poseidon satellite

• Global Positioning System

• sonar

Remote Sensing• Until recently, mapmakers had to go on-site to

collect the data needed to make maps.

Remote Sensing

• Today, advanced technology has changed the way maps are made.

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

The Electromagnetic Spectrum• Satellites detect different wavelengths of energy

reflected or emitted from Earth’s surface.

Remote Sensing

• This energy has both electric and magnetic properties and is referred to as electromagnetic radiation.

• Electromagnetic radiation includes visible light, gamma rays, X rays, ultraviolet waves, infrared waves, radio waves, and microwaves.

The Electromagnetic Spectrum

Wave Characteristics

Remote Sensing

– All electromagnetic waves travel at the speed of 300 000 km/s in a vacuum, a value commonly referred to as the speed of light.

– Electromagnetic waves have distinct wavelengths and frequencies.

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

– Frequency is the number of waves that pass a particular point each second.

– These unique characteristics help determine how the energy is used by different satellites to map Earth.

The Electromagnetic Spectrum

Wave Characteristics

Remote Sensing

Landsat Satellites• A Landsat satellite receives reflected

wavelengths of energy emitted by Earth’s surface, including some wavelengths of visible light and infrared radiation.

Remote Sensing

• Since the features on Earth’s surface radiate warmth at slightly different frequencies, they show up as different colors in images

Topex/Poseidon Satellite• The Topex/Poseidon satellite uses radar to

accurately map the ocean surface.

Remote Sensing

• Radar uses high-frequency signals that are transmitted from the satellite to the surface of the ocean.

• A receiving device then picks up the returning echo as it is reflected off the water.

Topex/Poseidon Satellite• The distance to the water’s surface is

calculated using the known speed of light and the time it takes for the signal to be reflected.

Remote Sensing

• Variations in time indicate the presence of certain features on the ocean floor as well as many ocean surface features and currents.

The Global Positioning System• The Global Positioning System, or GPS, is a

radio-navigation system of at least 24 satellites that allows its users to determine their exact position on Earth.

Remote Sensing

• Each satellite orbits Earth and transmits high-frequency microwaves that contain information about the satellite’s position and the time of transmission.

• A GPS receiver calculates the user’s precise latitude and longitude by processing the signals emitted by multiple satellites.

Sea Beam• Sea Beam technology is similar to the Topex/

Poseidon satellite in that it is used to map the ocean floor.

Remote Sensing

• Sea Beam is located on a ship and relies on sonar to map ocean-floor features.

• Sonar is the use of sound waves to detect and measure objects underwater.

Sea Beam• First, a sound wave is sent from a ship toward the

ocean floor.

Remote Sensing

• A receiving device then picks up the returning echo when it bounces off the seafloor.

• Computers on the ship can then calculate the distance to the ocean bottom based on the time it takes the signal to be reflected.