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## Models of the Earth: Using and Interpreting Maps

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Title: Models of the Earth: Using and Interpreting Maps

1
Models of the Earth Using and Interpreting Maps
• Finding Locations on Earth
• Mapping the Earths Surface
• Topographic Maps

2
Thought Question
• What is the purpose of maps?
• How are positions on planet Earth
represented/located?
• Explain how you would go about creating a map by
hand. What kinds of tools would you need? What
variables would you need to consider?

3
Objectives
• Distinguish between latitude and longitude
• Explain how latitude and longitude can be used to
find a location on Earth
• Explain how a magnetic compass can be used to
find directions on Earth
• Describe the characteristics and uses of three
types of map projections
• Define scale and explain how it can be used to
find distance on maps
• Explain how elevation and topography can be shown
on a map
• Interpret a topographic map

4
Why Maps?
• For thousands of years, people have used maps
• to define borders and to find places.
• Cartography is the science of mapmaking.
• 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.

5
Latitude
• Parallels- imaginary circles running east/west on
the globe determine how far north/south one is
named because they parallel the equator
• Latitude- the angular distance from north and
south of the Equator measured in degrees (90
intervals)
• Latitudinal Great Circle- Equator is the only
latitudinal great circle (any line that separates
the earth into two equal parts)

6
Latitude
• Latitude is thus measured from 0 at the equator
to 90 at the poles.
• 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).

7
Longitude
• Meridians- lines running north/south on the
globe, pole to pole determine how far east/west
one is
• Prime Meridian- the point 0 longitude runs
through Greenwich, England
• Longitude- the angular distance east or west of
the Prime Meridian all measured from 0- 180
east or west of the Prime Meridian
• Longitudinal Great Circles- any two meridians
running directly opposite (180) from one
another bisect the globe

8
Longitude
• Points west of the prime meridian are numbered
from 0 to 180 west longitude (W).
• Points east of the prime meridian are numbered
from 0 to 180 east longitude (E).

9
Locating Places with Coordinates
• Both latitude and longitude are needed to
precisely locate positions on Earth.
• For example, the location of New Orleans is
2957N, 9004W.
• Note that latitude comes first in reference to
the coordinates of a particular location.

10
Assessment
• Match the following terms with their definitions.
• ___ latitude
• ___ longitude
• ___ prime meridian
• ___ equator

D B A C
A. the reference point for longitude B. the
distance in degrees east or west of 0 C. the
reference point for latitude D. the distance in
degrees north or south of 0
11
Assessment
• Identify whether the following statements are
true or false.

false true false true
_______ A degree of longitude always represents
the same distance. _______ If you travel west
across the International Date Line, you advance
your calendar one day. _______ Lines of latitude
are not perfectly parallel to each
other. _______ When referencing a specific place
on Earth by its coordinates, latitude always
comes first.
12
Direction Finding
• Geomagnetic Poles- the point above the earths
poles where all magnetic lines converge
• The earth behaves as a giant magnet with areas
near the north and south pole acting as the ends
of the magnet this affects compasses different
amounts in different areas
• Magnetic Declination- the angle between the
direction of the earths geographic pole and the
direction in which a compass needle points
• True North- direction of the geographic north
pole

13
Thought Question
• Describe one type of map that you have seen or
used. What symbols are used? How are land forms
depicted? Name the type of map if you know it.
• What fields of science use maps and what are the
maps used for?
• Compare and contrast magnetic north and true
north.

14
Mapping The Earths Surface
• Maps are flat models of a three-dimensional
object, Earth.
• 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 globes surface onto a sheet of
paper.
• Map Projection- any flat map that is a
representation of a three dimensional object
three types Mercator, Gnomonic, and Conic

15
Mercator Projection
• Mercator- a map projection in which both the
meridians (evenly spaced) and parallels (unevenly
spaced) are straight and parallel, forming a grid

16
Gnomonic Projection
Gnomonic- parallels appear unevenly spaced,
concentric circles meridians appear as straight
lines radiating from a central point all great
circles appear as straight lines
17
Conic Projections
• Conic- meridians converge at the poles the
parallels appear as equally spaced, concentric
curves
• Polyconic Projection- several conic projections
put together to form a larger map

18
• Legend- the portion of a map that lists all
symbols and their meanings, distances, and
• Map Direction- maps are usually drawn with north
at the top of the page and south at the bottom
• Scale- the comparison of the distance on the map
to the actual distance covered
• 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 163 500.

19
Topographic Maps
• Topographic Map- scientific maps that show
surface features (such as mountains and valleys)
by using contour intervals changes 3D into 2D
• Topographic maps use lines, symbols, and colors
to represent changes in elevation and features on
Earths surface.
• Topography- surface features of the earth
• Elevation- the height, in feet or meters, above
or below sea level
• Mean Sea Level- the point located between the
highest and lowest tide levels of the ocean

20
Topographic Maps
21
Making Topo Maps
• Contour Lines-lines on a map that connect points
of the same elevation
• Contour Interval- the difference (in feet or
meters) from one contour line to the next
• Relief- the change in elevation from the lowest
to the highest points of an area sometimes
referred to as vertical relief
• Index Contours- every fifth contour line on a
topo map generally bold

22
3D to 2D
23
Depression Contours
• 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.

24
Section Assessment
• Match the following terms with their
definitions.
• ___ projection
• ___ contour interval
• ___ map legend
• ___ map scale

A. the difference in elevation between two
side-by-side contour lines B. a diagram that
explains what the symbols on a map
represent C. a map made by transferring points
and lines on a globes surface onto a sheet of
paper D. the ratio between distances on a map and
actual distances on the surface of Earth
C A D B
25
Section Assessment
• What does it mean if a map says Scale 1100
000?

This fractional scale means that one unit on the
map represents 100 000 units on Earths surface.
For example, one inch on the map would equal 100
000 inches on Earths surface.