GPS Basics
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Latitude lines run east to west and measure degrees north or south of the equator, while longitude lines run north to south and measure degrees east or west of the prime meridian. GPS (Global Positioning System) uses satellites to pinpoint locations on Earth by calculating distances to receivers using latitude and longitude coordinates. GPS is widely used for navigation, by the military, and in activities like geocaching where users locate hidden items using their GPS coordinates.
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GPS Basics
- 1. GPS
- 9. Latitude Lines The lines run east and west, but they measure degrees north or south of the equator. Equator – 0 o
- 10. Longitude Lines… … run north and south. Where do all the lines meet? Instead of measuring from the equator, longitude is measured from the prime meridian, a line running through Greenwich, England. Prime Meridian – 0 o
- 11. By combining latitude and longitude We can pinpoint any location on Earth.
- 12. We measure latitude and longitude in degrees. There are 360 degrees in a circle. One degree is 1/360 th the way around the earth.
- 13. We identify points on the Earth by specifying how many degrees North or South (of the equator) And how many degrees East or West (of the prime meridian) the points are located.
- 14. GPS Global Positioning System
- 15. GPS is used by millions of people around the world everyday. One of the earliest uses of the GPS was by the military branches. The soldier on the left is using a GPS to map a location for troops to land on a beach. Other uses by the military include tracking soldiers, vehicles, and supplies.
- 16. GPS is used to help locate people who have On-Star in their vehicles. On-Star is a safety and security system in cars and trucks created to connect drivers to emergency assistance and hands-free calling. Portable GPS systems are placed in vehicles to help people find their way to a destination.
- 17. GPS is used in boats to help in case of emergencies such as storms or engine failures.
- 18. GeoCACHING is a new sport that uses GPS to find hidden items or messages left by members of GeoCACHING clubs. People can look for these items if they know the latitude and longitude of the items.
- 19. This man is using a GPS to conduct water-typing surveys on Washington state’s Lopez and Orcas Islands. The surveys are being conducted on certain streams to determine the distribution of fish and fish habitat, and to ensure that the Island's trout and salmon streams are mapped correctly so they can receive appropriate legal protection.
- 20. How does the GPS help people in all these different situations?
- 21. How GPS (Global Positioning System) Works: Credit: http://nasaexplores.com
- 27. This illustration shows how the GPS receiver can see the satellites as they pass overhead. NASA/JPL
- 29. http://www.pbs.org/wgbh/nova/shackletonexped/navigate/gps/gps02.html “ Doing the Math” with GPS
- 30. http://www.pbs.org/wgbh/nova/shackletonexped/navigate/gps/gps03.html “ Doing the Math” with GPS
- 31. http://www.pbs.org/wgbh/nova/shackletonexped/navigate/gps/gps04.html “ Doing the Math” with GPS
- 32. http://www.pbs.org/wgbh/nova/shackletonexped/navigate/gps/gps05.html “ Doing the Math” with GPS
- 33. http://www.pbs.org/wgbh/nova/shackletonexped/navigate/gps/gps06.html “ Doing the Math” with GPS
- 34. http://www.pbs.org/wgbh/nova/shackletonexped/navigate/gps/gps07.html “ Doing the Math” with GPS
- 35. http://www.pbs.org/wgbh/nova/shackletonexped/navigate/gps/gps08.html “ Doing the Math” with GPS
- 36. http://www.pbs.org/wgbh/nova/shackletonexped/navigate/gps/gps09.html “ Doing the Math” with GPS
- 37. http://www.pbs.org/wgbh/nova/shackletonexped/navigate/gps/gps10.html “ Doing the Math” with GPS
- 38. http://www.pbs.org/wgbh/nova/shackletonexped/navigate/gps/gps11.html “ Doing the Math” with GPS
- 39. http://www.pbs.org/wgbh/nova/shackletonexped/navigate/gps/gps12.html “ Doing the Math” with GPS
- 40. http://www.pbs.org/wgbh/nova/shackletonexped/navigate/gps/gps13.html “ Doing the Math” with GPS
- 41. http://www.pbs.org/wgbh/nova/shackletonexped/navigate/gps/gps13b.html “ Doing the Math” with GPS You are here… … not up here!
- 42. You’ve discovered that you are in Montgomery, Alabama! Your GPS receiver figures all this out in less than a second. The GPS works by knowing the time of both the satellite and the GPS receiver.
- 43. Garmin GPS 72 Power Page Quit (Works like “Esc” or “Back”)
- 44. What to look for and record Longitude Latitude Elevation Satellites
Editor's Notes
- Teachers: Please read through the attached notes. You may not want to use all of the following information. Some may be too advanced for certain grade levels. The amount of time you have to teach will also determine how much explanation you will cover with each slide. Some information could be used just to help your understanding of how a GPS works. Please read through and choose what is best for your students. Option One: The next 5 slides can be used as a pretest with students putting answers on paper or you may call on individual students to answer as you go through the slides. “ We will take a short quiz to determine our knowledge of the GPS System. Number your paper 1-5. Write down the letter of the correct answer.” After the pretest go over the answers quickly. Option Two: Take out a piece of paper and a pencil. Fold the paper in three columns. K W L Ask the students to work in groups find out what they know. Then ask each group to give you one thing they know. The students can record under the L what they learn during this 2 to 3 minute discussion. Take 1 minute and let the students record other questions that they would like to know about the GPS. Example: How much do they cost? Next show the slides and call on students to answer and add to their KWL.
- A. East/West
- B. North/South
- B. Global Positioning System
- D. All of the above.
- C. Satellites
- Notice how the angles are figured. The next couple of slides will give more detail and will refer back to this slide.
- Teacher information: Starting at the equator 0 degrees latitude as we go to the north pole it is like climbing a ladder 10, 20, 30, 40, 50, 60, 70, 80, 90 degrees North. Also starting at 0 degrees latitude as we travel south 10, 20, 30, 40, 50, 60, 70, 80, 90 degrees South. (Like going down the ladder) Notice that there is a 20 ° latitude line in the northern hemisphere and there is also 20 ° in the southern hemisphere. It is very important to label the degree of latitude correctly with N or S to indicate the correct hemisphere. Refer to slide #7. Notice how the earth has been divided by the lines drawn using lines of latitude. Notice how the angles are measured.
- All the lines meet at the North and South Poles. For teacher understanding: The Earth has been sliced into 360 ° slices. They are numbered from 0 ° -180 ° . The lines start at 0 ° and go to 180 ° east and 180 ° west of 0 °. 180°is opposite from the Prime Meridian and is called the International Date Line. Degrees are measured by the angle that is made from the 0° to the longitude line. The center of the earth is the corner of the angle. Refer to slide #7.
- When the latitude and longitude lines are overlapped a grid forms. The grid helps us to find locations on Earth. When correctly labeled, a location is unique and there is none other on Earth like it.
- Fold a circle in half and continue to fold in half. Unfold and notice the lines. They look like the lines in the Illustration above. Label the equator 0°. Measure the line perpendicular to the equator using a protractor. You can see how the 90° latitude is drawn.
- Looking at the map, between what two latitude lines is Alabama located? 30-35 degrees. Point out to students that there are also lines between the 30 -35. ( 31, 32, 33, 34 and smaller lines in between) Between which 2 lines of longitude is Alabama located? 80 -90 degrees Have students estimate where their school is located.
- GPS is used by millions of people around the world every day. One of the earliest uses of the GPS was by the military branches. This soldier is using a GPS to map a location for troops to land on a beach. He is finding the exact latitude and longitude of where he is and then he will radio his location to the other troops. They will use a GPS to locate him using his coordinates. Other uses by the military include tracking soldiers, vehicles, and supplies. Civilians began to use the GPS around the year 2000.
- On-Star is a commercial use of the GPS system. It is found in vehicles.
- GPS can also help fisherman mark and locate the best places to fish. By knowing the exact latitude and longitude, the fisherman can return to the fishing site. This is not like a depth finder or sonar. GPS only measures location. (latitude and longitude)
- Google “Geocaching” to find places to visit and rules of each game. Latitude and longitude is given for the places you are to find. You use a GPS to find the latitude and longitude.
- He does this by finding the exact longitude and latitude so it can be matched to maps.
- The GPS system uses a network of satellites which circle the earth. Although only 24 are in use at any one time, there are often extra satellites in orbit waiting to be used as replacements. There may be as many as 28 GPS satellites in the sky at once. *Look at the red dot. This represents a person with a GPS on Earth. Watch as the satellites lock on. Notice as it goes around, it can only lock on to satellites which can receive the signal. The earth, distance, and movement out of range are some reasons a GPS does not lock on to a satellite. For example, if I were to go on the other side of the wall and ask you what I had in my hand, you could not tell me because you could not see it. A satellite that has a solid object between it and a GPS will not be able to exchange signals. (Tree cover, roof, tall buildings, road cuts through mountains, tunnels) *(Additional information for middles school students if needed )The Global Positioning System of satellite based navigation was incubated in the mind of Ivan Getting. Bradford Parkinson of the U.S. Air Force, who helped create GPS in 1972 and Roger Easton, of the U.S. Navy research Laboratory, who filed the enabling patent in 1974. It was originally developed by the Department of Defense to meet military requirements. Approximately $12 billion was spent to develop the program. In early 1978, Satellites known as Block-I was launched with ten more to follow in 1985. These were replaced by Block II in 1989. In January 1994 a complete constellation of 24 satellites were in placed. The GPS navigation data is operated and controlled by the 50 th Space wing, located at Schriever Air Force Base Colorado. The Delta II expendable launch vehicle is used to launch GPS satellites from Cape Canaveral Air Station, FL. The satellites are designed to have a life of 7.5 years, but many are lasting more than 10-12 years.
- Picture = boat with a GPS unit. The colored circles represent the distances around satellites as they lock on to the GPS. The boat is on the outside circle of each of the satellites. Notice it is where all the circles overlap and meet.
- You need to lock on to 3 or more satellites. The more satellites the better the accuracy of your location.
- Your GPS is sending different signals that match each of the satellites in orbit. Notice the illustration shows a signal from the GPS and from a satellite. The patterns match, only one has not “caught” up with the other one because it is having to travel from a great distance. Think of a teacher who has a student (John) in the office and one (Sarah) in the same room. Both students are holding a yellow pencil and can hear the teacher because the intercom is on in both places. The teacher tells John and Sarah to hand her a yellow pencil. Both students respond by taking a pencil to the teacher. Which one is able to hand over the pencil first? Sarah who is in the room can hand over the pencil first because she is closer. This is like the signal from the GPS on Earth. John can hand over a pencil also, but he has to travel from the office to the room. He has the same yellow pencil but his arrives a little later. This is like the signal traveling from the satellite. It is the same but just takes a little longer to reach the teacher.
- The GPS is sending signals and doing the math to determine how far away the satellite is. It does this in less than a second. Every time you move with the GPS it redoes the math because your distance from the satellite has changed.
- You keep locking in to satellites until the GPS has acquired all the satellites possible at that moment. The more, the better the accuracy.
- You’ll see that there are two places you could be. However, your GPS easily discards one of them as it puts you some 100 miles above the surface of the earth. By combining the latitude and longitude of where you are the satellites can locate you anywhere on Earth.
- Your GPS receiver figures all this out in less than a second. The GPS works by knowing the time of both the satellite and the GPS receiver. They both are using the same time.
- The “Power” button looks like a little red light bulb. Press and hold for about 1-2 seconds to turn the unit off or on. The “Page” button will step through the various pages, or screen displays, which are available on the GPS. The “Quit” button (lower left) works like an “Esc” or “back” button on your computer. If you press something you didn’t mean to, just use the “Quit” button to go back where you started from.
- This screen is called the Main Information page. There are several other pages, such as a compass and a map. This page is the one we will use for our activities today. If you do not see this page on your GPS, press the “Page” button to step through the pages until you get here. This page also tells you date, time, and accuracy of your location. The GPS should be set up in metric system. The smaller the number of accuracy means the more accurate your location. Imagine a circle drawn around you. The radius of the circle is measured from you in the center to the edge of the circle. The smaller the number means the edge of the circle is closer to you.
- These instructions allow you to put your GPS into simulator mode, so that while you are indoors you can see what the screen will look like. Remember that in simulator mode you are not actually receiving any signals, so the lat/long numbers are not accurate. Be sure to exit the simulator mode before using the GPS outdoors. You should be able to exit the simulator by pressing “Quit” or by turning the unit off and back on.
- Now that you know how the GPS works, let’s go outside and explore! Just to recap—to start the GPS: Turn the red button on Press the Page button to accept the disclaimer message You should see the “Acquiring Satellites” message for about 1-2 minutes. If the GPS jumps to the map page, press “Page” until it returns to the Main Info page. Go have fun!