GPS

Presented by

Technology Integration HRSB

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.

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

Accuracy of GPS

• Basic Units– Accurate up to 1 meter

• Advanced Units– Accurate up to 1 centimeter

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

Three Segments

Three Parts to GPS

• Satellites– 24 satellites (21 are active with 3 spares)– 12,000 miles above the Earth’s 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

Satellites Con’t.

• First launched in 1978

• Full 24 satellites by 1994

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)

Satellite Information

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

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

Use Segment (GPS)

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

How it all works together…

Source of Errors

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

A

B

C

D

Use of GPS: Research

GPS: Recreation

WaypointsA waypoint is a “position stored in the unit’s 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

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)

Uses in the ClassroomElementary

• Physical Education Con’t.– 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

Using the etrex Legend GPS Unit

The Keys

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.

When you are done use the thumb stick to highlight the ok button and press the thumb stick button once.

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.

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.

Step 5 - Use the THUMB STICK button toselect 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.

Adapted from http://sciencespot.net/Media/GPSGarminTips.pdf