South Carolina Geographic Alliance
Global Positioning Systems
for the Classroom
Mark Musselman
Audubon Center at
Francis Beidler Forest
Harleyville, South Carolina
Where is the SC Geographic Alliance?
Southeast of the Lawmakers
Capitol
East of the Books
Library and
reflecting pool
Southeast of the Old Campus
Horseshoe
Close to Campus Dining
Russell House
The Callcott Building
The SCGA is here!
Where is the SCGA?
Would any of the previous descriptions have been sufficient
for a person to find the SCGA in this building?
Maybe, but is there a more precise method to describe your
location on the Earth’s surface?
Photo credit: NASA
Latitude and Longitude
Angles measure in degrees, minutes, and seconds of an arc.
Latitude and Longitude
Latitude (is "fatitude" around the waist of the Earth)
measured north and south of the Equator
Latitude and Longitude
Longitude measured east and west of the Prime Meridian
Latitude and Longitude
Minutes (represented as ' ) and seconds
(represented as '' ) of arc are different than the
minutes and seconds on a clock.
1o=60'=3600''
In fact...
1 hour of Earth's rotation covers 15o longitude
(360o/24 hrs = 15o)
Latitude and Longitude
Key lines of latitude are:
Equator (0o) divides the Earth into the
Northern and Southern Hemispheres
Latitude and Longitude
Key lines of latitude are:
North Pole (actually, a point at 90oN)
Latitude and Longitude
Key lines of latitude are:
South Pole (actually, a point at (-90o or 90oS)
Latitude and Longitude
Key lines of latitude are:
Tropic of Cancer (23.5oN)
Latitude and Longitude
Key lines of latitude are:
Tropic of Capricorn (-23.5o or 23.5oS)
Latitude and Longitude
Key lines of longitude are:
Prime Meridian (0o): The Western and Eastern Hemispheres
are measured west and east of the Prime Meridian to where
they meet at the 180th Meridian
180th Meridian: (180oE and 180oW, generally the
International Date Line)
Latitude and Longitude
The combination of a latitude coordinate and a longitude
coordinate designates a unique point on the surface of the Earth.
For example…
True or false: xoS/yoW is not a point within the United States.
Latitude and Longitude
True
Even without values for x and y (xoS/yoW ), you can
answer that the statement is true because no U. S. points
lie within the Southern Hemisphere.
Global Positioning System
The basis of GPS is triangulation from a selection
of the 24 satellites in known Earth orbit.
Global Positioning System
To "triangulate," a GPS receiver (GPSr) measures
distance between the receiver and the satellites
using the travel time of radio signals.
speed x time = distance
where speed is
assumed
to be 300,000 km/s
(speed of light)
Global Positioning System
Mathematically four satellite ranges are needed to
determine exact position. Three are enough if we reject
ridiculous answers (points in the center of the Earth or high
in the atmosphere).
Global Positioning System
GPSr accuracy is diminished by:
 Clock inaccuracies within satellites
 Satellite location inaccuracies
 Atmospheric signal interference
 Signal interference caused by obstructions (trees,
buildings, mountains, etc.)
 Number of satellites available to the user (above the
horizon) and their positions in relation to each other
Basic GPSr Operation
How can I identify a GPSr?
Basic GPSr Operation
Power up!
Press and hold the bottom
right button until the welcome
page appears.
Basic GPSr Operation
Getting started!
Press the top button three times.
The satellite page will appear.
Scroll through the pages by
continuing to push this button.
Basic GPSr Operation
Basic GPSr Operation
Basic GPSr Operation
Satellite Page
Basic GPSr Operation
You are here
Basic GPSr Operation
Marking your position – waypoint
Press the “mark” button and your current position
(coordinates) will be shown with a default 3-digit name
assigned to the waypoint.
Basic GPSr Operation
Marking your position – waypoint
A waypoint is a “point along the way.” It may be somewhere
you’ve never been or a place to which you wish to return.
Press OK to save the waypoint with the assigned name – in
this case, it is 001.
Basic GPSr Operation
Marking your position –waypoint
To change the waypoint name, toggle
down until 001 is highlighted.
Press the center of the thumb stick to
reveal the keyboard.
Toggle across the keyboard to edit.
Basic GPSr Operation
Entering waypoints in advance
Waypoints can be downloaded directly
from a computer using free software
such as EasyGPS at
http://www.easygps.com, which
accommodates most GPS models.
For example, all 280 waypoints of the
Foothills Trail in SC are available at
http://www.travelbygps.com/premium/foot
hills/foothills.php
Basic GPSr Operation
Entering waypoints in advance
With a few clicks of the mouse, all the data for the Foothills
Trail can be loaded to your GPS unit!
Basic GPSr Operation
Entering waypoints in
advance
Pre-trip waypoints can be
displayed on topographic
maps, which can be
loaded to a GPS unit.
A desire for the easiest
route is all the motivation
one needs to understand
contour lines.
Basic GPSr Operation
Entering waypoints in advance
Just as the name can be changed, so too
can the location (coordinates).
Toggle down until the location field is
highlighted.
Press the center of the thumb stick to reveal
a number keypad for editing.
Basic GPSr Operation
Navigating to your waypoint
If you have a waypoint already displayed,
simply toggle to the Goto button and press
the center of the thumb stick.
Basic GPSr Operation
Navigating to your waypoint
If you already have waypoints loaded to your
unit, press the bottom button on the left side
to reveal the options. Select “Waypoints”.
Waypoints may be displayed by name or by
the nearest to your current position.
Basic GPSr Operation
Navigation Page
Basic GPSr Operation
Navigation Page
After selecting to “Goto” a
waypoint, the compass
navigation page will
appear.
The compass is a graphic
and not magnetic, so it
likely will not be pointing
toward the correct
direction of travel.
Once you begin to move,
it will orient properly with
the arrow pointing toward
the destination.
Basic GPSr Operation
Navigation Page
An inexpensive magnetic compass and a map are essential
items in the event your GPS unit fails to operate.
Basic GPSr Operation
Navigation Page
Turn off the unit whenever practical to
conserve battery life. Remember, batteries
will ALWAYS fail at the most inconvenient
moment.
Push and hold button until screen clears.
Geocaching
What is a Cache?
What is a Cache?
Cache - (kash) n. 1. a hiding
place for treasure or provisions.
2. hidden treasure or provisions.
(caching, v.) to place in a cache
Cache Name
Cache Waypoint
Cache Coordinates
Cache Rating
Cache Size
Cache Information
Cache Clues and Links
Clue and key
Links
Cache Page Log
Conclusion
GPS technology continues to be
incorporated into various aspects of our
society. Understanding the concepts
behind the technology as well as its use
not only helps students address
curriculum standards, it is an everincreasing employment skill.
A simple campus-based navigation
course, geocaching, or incorporation
within the curriculum are easy, effective
methods for teaching students GPS skills
and technology!