GPS

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GPS

• Presented by
• Technology Integration HRSB

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What is GPS?

• Global Positioning System
• A Network of satellites that continuously
  transmit coded information, which makes it
  possible to precisely identify locations on earth
  by measuring distance from the satellites.

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How did GPS Start?

• Satellites (24) developed by the U.S. Department
  of Defense.
• Cost billions of dollars to develop and maintain.
• Originally designed for military use
• Navigation
• Troop Deployment
• Artillery Fire

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Accuracy of GPS

• Basic Units
• Accurate up to 1 meter
• Advanced Units
• Accurate up to 1 centimeter

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GPS Uses

• Can be used anywhere except places where it is
  impossible to receive a signal
• Classroom (inside buildings)
• Underground
• Caves
• Land, Air and Sea!
• Commercial aircraft

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Three Segments
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Three Parts to GPS

• Satellites
• 24 satellites (21 are active with 3 spares)
• 12,000 miles above the Earths surface
• Traveling at speeds of 7,000 miles/hour
• Circle the Earth every 12 hours
• Powered by solar energy with back up battery
  (i.e. during solar eclipse)
• Small rocket boosters to keep them flying in the
  correct path

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Satellites Cont.

• First launched in 1978
• Full 24 satellites by 1994

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Coded Signals

• Main purpose is to allow for calculating the
  travel time from the satellite to the GPS
  receiver on Earth (Time of Arrival)
• Travel Time x Speed of Light Distance from
  Satellite to GPS Receiver (Satellite Range)

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Satellite Information

• The Navigation Message contains
• Satellite orbital information
• Clock information
• General system status message

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Control Segment

• Five Control Stations
• Located around the world
• 4 unmanned
• Hawaii and Kwajalein in the Pacific Ocean Diego
  Garcia in the Indian Ocean Ascension Island in
  the Atlantic Ocean.
• 1 master control centre
• Colorado Springs, Colorado

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Use Segment (GPS)

• You and your GPS unit
• Boaters
• Pilots
• Hikers
• Hunters
• Military
• Recreation (Geocaching)

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How it all works together
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Source of Errors
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How it works

• 5 seconds to reach unit, 500 km from Satellite A
• 4.5 seconds to reach unit, 450 km from Satellite
  B
• 4.25 seconds to reach unit, 425 km from Satellite
  C
• 7 seconds to reach unit, 700 km from Satellite D
• Distances are calculated by the length of time it
  takes the signal to reach the satellite
• With these four readings the exact latitude,
  longitude and altitude can be determined for the
  GPS Unit location

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Use of GPS Research
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GPS Recreation
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Waypoints

• A waypoint is a position stored in the units
  memory used for direct navigation or to build a
  route.
• How to create a waypoint
• 1) You can mark your current location as a
  waypoint
• Press the ENTER/MARK key while present at the
  location you want to record as a waypoint,
  highlight OK and press ENTER to save OR...
• 2) You can manually enter existing coordinates
• Press and hold ENTER/MARK until Mark Waypoint
  page is displayed
• Use ROCKER to highlight location, press ENTER and
  change the coordinates using the ROCKER button
• Highlight OK and press ENTER to save

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Uses in the ClassroomElementary

• Health Education
• B7.1 Engage in regular physical activity.
• Physical Education
• Experience walking around the school observing
  landmarks and being conscious of litter and the
  environment
• Experience walking as quietly as possible as a
  measure of sensitivity to the environment
• Experience playing a game in a variety of
  environments (e.g. hide and seek in a wooded
  restricted area, snow-golf)
• Experience using a community resource to
  participate in physical activity (e.g. pool,
  rink)

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Uses in the ClassroomElementary

• Physical Education Cont.
• Experience and outdoor activity in each of the
  four seasons
• participate in a walking or jogging program in
  preparation for hiking, orienteering, cross
  country skiing.
• Follow directions and symbols on a map of the
  school grounds, locating specific landmarks
• Take part in an activity utilizing a community
  resource (physical or human)
• Participate in games, sports, dance and outdoor
  pursuits, both in and outside school, based on
  individual interests and capabilities
• Participate in an orienteering-type activity
  using a map and compass on the school grounds or
  at a local park

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Using the etrex Legend GPS Unit
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The Keys
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• The Keys

Display Screens
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Satellite Page
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Marking Your Location (waypoint)
Press and hold the Thumb Stick until the Mark
Waypoint screen appears with the guy holding a
flag
Your waypoint is already assigned a three digit
number. To change the name of the waypoint, use
the thumb stick button to highlight its name.
Use the thumb stick to set a new name for the
waypoint.
To change the waypoint, use the thumb stick to
highlight the numbers. Use the thumb stick to
navigate the number pad and change the waypoint.
When you are done use the thumb stick to
highlight the ok button and press the thumb stick
button once.
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Finding a waypoint
Step 1 Use the PAGE button to find the main
menu. Use the THUMB STICK to go to the FIND
option and press the same button to select this
option.
Step 2 Select WAYPOINTS by pressing the THUMB
STICK button.
Step 3 Choose NEAREST on the next menu.
Step 4 Select the waypoint you want using the
THUMB STICK button.
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Finding a waypoint cont..
Step 5 - Use the THUMB STICK button to select
GOTO at the bottom of the screen.
Step 6 - Use the navigation screen to help you
locate your destination. You need to move in the
direction of the large arrow. When you get close
to your destination, an Arriving at Destination
message will be displayed.
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Adapted from http//sciencespot.net/Media/GPSGarmi
nTips.pdf