This document provides information about latitude and longitude, different map projections, topographic maps, and remote sensing. It defines key terms and concepts and describes how cartographers use lines of latitude and longitude to locate positions on Earth. It also explains how different map projections, such as Mercator and conic, represent the globe on a flat surface and how topographic maps use contour lines to show elevation changes. The document concludes by discussing how satellites, sonar, and GPS are used in remote sensing to map and study Earth's surface and oceans from a distance.

1. 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

2. • 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

3. 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.

4. 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).

5. 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.

6. 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.

7. 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).

8. 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

9. 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.

10. 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

11. 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.

12. Time Zones
• There are six
different time
zones in the
United States.
Latitude and Longitude

13. 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.

14. 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

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

20. 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.

21. 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.

22. 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.

23. 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.

24. 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.

25. • 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

26. • 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

27. 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.

28. • 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

29. 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.

30. 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.

31. 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.

32. The Electromagnetic Spectrum
Wave Characteristics
Remote Sensing

33. 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

34. 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.

35. 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.

36. 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.

37. 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.

38. 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.