Introduction to Mapping

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.