NAME________________________________
DATE___________________
PARTNER(S)__________________________
COORDINATE SYSTEMS: LOCATING YOURSELF ON A SPHERE
Activity 1: Getting Your Bearings
1.
Close your eyes and point to the north.
Did you point up? Why or why not?
“Up” is the #1 answer. Think about this response when you answer the next question.
Imagine that you were hiking along a trail and the trail suddenly divides. You know that
you have to go north. How would you know which way to proceed?
You know that you cannot go “up”; that makes no sense in this case. What you realize is that
north is a planar direction (front, back, sideways) in which you can move. You can use a
compass to direct you since the needle (dial) of the compass will point to the magnetic north
pole of the Earth (which is currently close to the geographic North Pole)
2.
Locate a compass and open it if necessary. The direction in
which the needle points is north. If the needle is color coded
rather than having an “N” printed on it, ask the instructor which
color represents north. Slowly turn the compass until the “N” on
the compass circumference lines up with the needle. What
region of the room is due (exactly) north?
Where would you end up if you walked to the southeast?
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Prince George’s Community College
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3.
Let’s think back to the most common answer to the question “Where is north?”. Looking
at a globe, locate the northernmost point on the globe. From your position near
Washington, D.C, where does north seem to be on the globe?
Think about how a person standing on Earth would be oriented. To help you imagine,
take a toothpick and break it in half. Take a small piece of clay and place it on
Washington, D.C. and place the stick in the clay to represent a person (obviously NOT to
scale!) standing upright. Would the person be looking “up” to the North Pole? Explain.
Activity 2: Using Latitude and Longitude Coordinates
Suppose you were asked to pinpoint your exact location on Earth. Can you do that with the
compass? Explain.
If you were in the middle of the ocean with no visible landmarks, would your system work?
Explain why or why not.
Look at one of the Earth globes in the classroom. Explain what the lines running east-west and
north-south might represent.
The best way to pinpoint your position is to use a grid system. Because planetary bodies like the
Earth and Moon are spherical, we need to employ a grid system on a curved surface. As you
may recall, the system currently in use defines the North and South Poles as reference points.
These points represent the imaginary positions where the rotation axis of the Earth emerges. The
current system employs grid lines that measure longitude and latitude.
Latitude
The equator is an east-west line that encircles the globe exactly midway between the north and
south poles. It is designated as 0o (zero degrees). Additional lines, parallel to the equator and
called parallels, are marked off to the north and south. These lines mark the angular distance
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Explorations in Earth and Space Science
PSC 121
Prince George’s Community College
from the equator, a measurement called latitude. Northern latitudes values are marked N or with
a plus (+) sign. Southern latitudes are marked with an S or minus (-) sign. The North Pole is
designated as 90oN or +90o while the South Pole is 90oS or -90o. See the illustration below for
parallels or lines of longitude. Your latitude is how many degrees north or south you are from
the equator.
Longitude
The series of north-south
lines which converge at
either pole are called
meridians or lines of
longitude. They divide
the 360o globe into eastwest sections. You can
see these on the diagram
here. On any planetary body, a prime meridian with a value of 0o must be defined so that values
can be assigned to the other lines of longitude. On Earth, the prime meridian passes through
Greenwich, England. Earth longitude is measured from 0 to 180o to the west and 0 to 180o to the
east. Your longitude is the number of degrees your site is east or west of the prime meridian.
You should note that values from 0 to 180o W are also sometimes designated as negative values
(-85o equals 85oW). On other planets, such as Mars, longitude values run from 0o to 360o and no
east-west direction is implied
So, using latitude and longitude, you can locate a position on any planet or moon. In this activity
you will explore site location on Earth, the Moon, and Mars.
1.
Using the map of the Earth at the end of this activity or an Earth globe, determine the
longitude and latitude of the following sites. An atlas is available from the instructor if
needed.
Point
Location
A
Big island of Hawaii
B
Central Iceland
C
Northernmost tip of New Zealand
D
Chesapeake Bay
Explorations in Earth and Space Science
Latitude
PSC 121
Longitude
Prince George’s Community College
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2.
There are approximately 140 known impact structures on the Earth made by space debris.
Plot and label the following crater locations on the Earth map printed at the end of this
activity.
Point
Crater
Latitude
Longitude
E
Meteor Crater, AZ, USA
35oN
111oW
F
Sudbury, Canada
47oN
81oW
G
Ust-Kara, Russia
69oN
65oE
H
Teague, Australia
26oS
121oE
I
Monturaqui, Chile
24oS
68oW
3.
Listed in the table below are actual landing sites for the Viking I and II (1976), the
Pathfinder (1997) Mars missions, and the Rover Mars missions (2004).
Site #
Landing
Site
Latitude
1
Viking 1
22oN
50oW
50o
2
Viking 2
48oN
134oE
226o
3
Pathfinder
19oN
34oW
34o
4
Spirit
15oS
176oE
184o
5
Opportunity
2oS
6oW
6o
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Earth System Mars System
Longitude
Longitude
Description
a.
Locate and describe these sites on the Mars map that is available. DO NOT
MAKE ANY MARKS ON THE MAP! Explain why you think these sites might
have been selected.
b.
Plot and label the same sites (same longitude and latitude) on the Earth map.
Would the Mars landers have been in trouble with any of these sites on Earth?
Explain.
Explorations in Earth and Space Science
PSC 121
Prince George’s Community College
4.
Using the National Geographic Society Earth’s Moon Map provided, answer the
following questions. DO NOT MAKE ANY MARKS ON THE MAP!
a.
Determine the latitude and longitude for the features listed in the table below:
(Use the indices on the front and back of the map for general area location.)
Feature
Latitude
Longitude
Copernicus (a crater)
Mendeleev (a crater)
Apollo 17 landing site
Surveyor 7 landing site
b.
List two features that the lunar prime meridian crosses:
________________________
c.
_____________________________
From lunar latitude and/or longitude values, explain how you could quickly
recognize that a feature is located on the far side of the Moon.
Explorations in Earth and Space Science
PSC 121
Prince George’s Community College
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Explorations in Earth and Space Science
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Prince George’s Community College
Activity 3: Locating Your Place on Earth Using GPS
So, now we know that we can pinpoint our Earth location by using longitude and latitude
coordinates. But, how do we know what these coordinates are for the location we are in now?
In the past, people have used the position of the stars and exact timekeeping devices. Today we
have a more sophisticated system that uses satellites. The Global Positioning System (GPS)
involves a series of satellites that beam signals to Earth. A GPS receiver can detect these signals.
If the receiver can pick up signals from four satellites, it can use the information to “triangulate”
and determine your exact longitude and latitude and velocity (if you are moving). The more
signals received, the more accurate the positioning. You can use this system on land or sea, and
most planes and boats are equipped with receivers for navigation. Today, some cars have built in
GPS navigation systems. GPS is funded by and controlled by the U. S. Department of Defense
(DOD). While there are many thousands of non-government users of GPS world wide, the
system was designed for and is operated by the U. S. military.
1.
Locate a GPS receiver (Magellan or Garmin) and take it outside the building. Turn the
receiver on. You will need to wait for a few minutes as the receiver locates satellite
signals. If the receiver is blocked by the buildings, move away into an open area (like a
courtyard or parking lot) until the receiver has registered enough satellites to give a
position.
Record your longitude and latitude here:
longitude___________________________
latitude___________________________
2.
While watching the receiver, walk some distance from your starting point.
Does your position change much? Why or why not?
3.
If you are using the Garmin receiver, notice the compass on the top of the display as you
are walking. Change direction and walk a distance in the new direction. What happens
to the display?
Why do you think there is a delay in the receiver response?
Explorations in Earth and Space Science
PSC 121
Prince George’s Community College
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Explorations in Earth and Space Science
PSC 121
Prince George’s Community College