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GPS Workshop. April 6, 2010 Hutterian Colony School Inservice Trevor Boehm / Cindy Chabot. The Challenge of Knowing Where You Are.
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GPS Workshop April 6, 2010 Hutterian Colony School Inservice Trevor Boehm / Cindy Chabot
The Challenge of KnowingWhere You Are • Our ancestors had to go to pretty extreme measures to keep from getting lost. They erected monumental landmarks, drafted detailed maps, and learned to read the stars in the night sky. • Things are much, much easier today. For a few hundred dollars, you can get a pocket-sized gadget that will tell you exactly where you are on earth at any moment. As long as you have a GPS receiver and a clear view of the sky, you'll never be lost again.
What is GPS? • GPS stands for “Global Positioning System”. • GPS permits land, sea, and airborne users to determine their three-dimensional position, velocity, and time 24 hours a day, in all weather, anywhere in the world. • The GPS system was developed and is operated by the U.S. Department of Defense. • When people talk about "a GPS," they usually mean a GPS receiver. The Global Positioning System (GPS) is actually a constellation of Earth-orbiting satellites. • The U.S. military developed and implemented this satellite network as a military navigation system, but soon opened it up to everybody else.
Parts of the GPS System Three parts or “segments”: • The Space Segment, consists of a minimum of 24 operational satellites in six circular orbits 20,200 km above the earth with a 12 hour period. The satellites are spaced in orbit so that at any time a minimum of 6 satellites will be in view to users anywhere in the world. The satellites continuously broadcast position and time data to users throughout the world. The satellite system was completed on March 9, 1994. • The Control Segment consists of a master control station at Falcon Air Force Base outside Colorado Springs, Colorado. There are also five monitor stations and four ground antennas located throughout the world. The monitor stations track all GPS satellites in view and send the information they collect back to the master control station. The information is then used to issue instructions to the satellites to keep them in the correct orbits. • The User Segment consists of the receivers, processors, and antennas that allow land, sea, or airborne operators to receive the GPS satellite broadcasts and compute their precise position, velocity and time.
The Satellites • There are 29 satellites – 24 operational ones and 5 spares (in case something breaks). • The satellites that make up the GPS space segment are orbiting the earth about 12,000 miles above us. • They are constantly moving, making two complete orbits in less than 24 hours. • These satellites are traveling at speeds of roughly 7,000 miles an hour. • GPS satellites are powered by solar energy. They have backup batteries onboard to keep them running in the event of a solar eclipse, when there's no solar power. Small rocket boosters on each satellite keep them flying in the correct path.
Launch of a GPS Satellite • A Boeing Delta II rocket successfully deployed a Global Positioning System, or GPS, satellite on March 31, 2003. • GPS IIR-9 was launched aboard a Delta II rocket from Space Launch Complex 17A, Cape Canaveral Air Force Station, Florida. • The rocket lifted off at 5:09 p.m. EST and the 68-minute mission ended with the successful delivery of the spacecraft into orbit.
What Does a GPS Receivcer Tell Us? • A GPS receiver must be locked on to the signal of at least 3 satellites to calculate a 2D position (latitude and longitude) and track movement. • With four or more satellites in view, the receiver can determine the user's 3D position (latitude, longitude and altitude). • Once the user's position has been determined, the GPS unit can calculate other information, such as speed, bearing, track, trip distance, distance to destination, sunrise and sunset time and more.
How a GPS Receiver Works • A GPS receiver's job is to locate three or more of these satellites, figure out the distance to each, and use this information to calculate its own location. • This operation is based on the mathematical principle called triangulation. • In order to make this simple calculation, then, the GPS receiver has to know two things: • The location of at least three satellites above you. • The distance between you and each of those satellites.
Triangulation – One Position • Imagine you are somewhere in the United States and you are TOTALLY lost -- for whatever reason, you have absolutely no clue where you are. You find a friendly local and ask, "Where am I?" He says, "You are 625 miles from Boise, Idaho." • This is a nice, hard fact, but it is not particularly useful by itself. You could be anywhere on a circle around Boise that has a radius of 625 miles.
Triangulation– Two Positions • You ask somebody else where you are, and she says, "You are 690 miles from Minneapolis, Minnesota. • Now you're getting somewhere. If you combine this information with the Boise information, you have two circles that intersect. You now know that you must be at one of these two intersection points, if you are 625 miles from Boise and 690 miles from Minneapolis.
Triangulation– Three Positions • If a third person tells you that you are 615 miles from Tucson, Arizona, you can eliminate one of the possibilities, because the third circle will only intersect with one of these points. • You now know exactly where you are -- Denver, Colorado.
3D Triangulation • That was a 2D example using circles. • The GPS receiver works in 3D space, meaning that we are dealing with spheres, not circles. But the principle is the same. • You need 4 spheres to figure out a position in 3D space... But the earth itself is a sphere, so you really only need three satellites, unless you want precise altitude information.
What’s In the Satellite Signals? • GPS satellites transmit two low power radio signals, designated L1 and L2. Civilian GPS uses the L1 frequency of 1575.42 MHz in the UHF band. • The signals travel by line of sight, meaning they will pass through clouds, glass and plastic but will not go through most solid objects such as buildings and mountains. • A GPS signal contains three different bits of information: • An ID code that identifies which satellite is transmitting information. You can view this number on your Garmin GPS unit's satellite page, as it identifies which satellites it's receiving. • Ephemeris data tells the GPS receiver where each GPS satellite should be at any time throughout the day. Each satellite transmits ephemeris data showing the orbital information for that satellite and for every other satellite in the system. • Almanac data, which is constantly transmitted by each satellite, contains important information about the status of the satellite (healthy or unhealthy), current date and time. This part of the signal is essential for determining a position.
How the ReceiverCalculates Your Position • We said the GPS receiver needs to know two things to figure out where you are: • The location of at least three satellites above you. • This comes directly from the satellites – the ephemeris data in the signal. • The distance between you and each of those satellites. • The GPS receiver does some math to get this information. • Radio waves are electromagnetic energy, which means they travel at the speed of light (about 300,000 km per second in a vacuum like space). • The receiver can figure out how far the signal has traveled by timing how long it took the signal to arrive. • The satellites send time information with their signals, and the GPS has an onboard clock. • This tells the receiver how far it is from each satellite.
GPS Errors Factors that can degrade the GPS signal and thus affect accuracy include the following: • Ionosphere and troposphere delays — The satellite signal slows as it passes through the atmosphere. The GPS system uses a built-in model that calculates an average amount of delay to partially correct for this type of error. • Signal multipath — This occurs when the GPS signal is reflected off objects such as tall buildings or large rock surfaces before it reaches the receiver. This increases the travel time of the signal, thereby causing errors. • Receiver clock errors — A receiver's built-in clock is not as accurate as the atomic clocks onboard the GPS satellites. Therefore, it may have very slight timing errors. • Orbital errors — Also known as ephemeris errors, these are inaccuracies of the satellite's reported location. • Number of satellites visible — The more satellites a GPS receiver can "see," the better the accuracy. Buildings, terrain, electronic interference, or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. GPS units typically will not work indoors, underwater or underground. • Satellite geometry/shading — This refers to the relative position of the satellites at any given time. Ideal satellite geometry exists when the satellites are located at wide angles relative to each other. Poor geometry results when the satellites are located in a line or in a tight grouping. • Intentional degradation of the satellite signal — Selective Availability (SA) is an intentional degradation of the signal once imposed by the U.S. Department of Defense. SA was intended to prevent military adversaries from using the highly accurate GPS signals. The government turned off SA in May 2000, which significantly improved the accuracy of civilian GPS receivers.
The Garmin GPSmap 60C Antenna Colour Screen Zoom Buttons Page Button Mark Button
Latitude and Longitude • Lines (parallels) of Latitude start at the equator, where the earth is the widest. • Latitude is measured in degrees and minutes north and south of the equator. • The equator divides the world into Northern and Southern Hemispheres. • Meridians of Longitude start at the prime meridian, which travels through Greenwich, England. • Longitude is measured in degrees and minutes east and west of the prime meridian. • The Prime Meridian divides the world into Eastern and Western Hemispheres.
How Latitude and Longitude Give Us a Global Position Grid • Latitude and longitude form a grid that can be used to indicate the position of any spot on the earth’s surface. • Maps are marked off in latitude and longitude. Your GPS displays latitude and longitude for your current location. • Winnipeg is located at 49°53’ N latitude and 97°09’ W longitude.
A Few More Terms • A track is where you’ve been. Your GPS shows your track as a line. • Waypoints are markers. Your GPS allows you to name your waypoints and give them icons. To set a waypoint, push the “mark” button on your GPS. • A route is the path from one spot to another.
Who Uses GPS? Who uses GPS? GPS has a variety of applications on land, at sea and in the air. • Basically, GPS is usable everywhere except where it's impossible to receive the signal such as inside most buildings, in caves and other subterranean locations, and underwater. • The most common airborne applications are for navigation by general aviation and commercial aircraft. • At sea, GPS is also typically used for navigation by recreational boaters, commercial fishermen, and professional mariners. • Land-based applications are more diverse. The scientific community uses GPS for its precision timing capability and position information. • Surveyors use GPS for an increasing portion of their work. GPS offers cost savings by drastically reducing setup time at the survey site and providing incredible accuracy. Basic survey units, costing thousands of dollars, can offer accuracies down to one meter. More expensive systems are available that can provide accuracies to within a centimeter. • Recreational uses of GPS are almost as varied as the number of recreational sports available. GPS is popular among hikers, hunters, snowmobilers, mountain bikers, and cross-country skiers, just to name a few. Anyone who needs to keep track of where he or she is, to find his or her way to a specified location, or know what direction and how fast he or she is going can utilize the benefits of the global positioning system. • GPS is now commonplace in automobiles as well. Some basic systems are in place and provide emergency roadside assistance at the push of a button (by transmitting your current position to a dispatch center). More sophisticated systems that show your position on a street map are also available. Currently these systems allow a driver to keep track of where he or she is and suggest the best route to follow to reach a designated location.
John Deere Green Star • The GreenStar AutoTrac System is a hands-free steering system for straight-line operations. It drives your tractor down straight lines. • To do this, it uses GPS technology to tell the tractor where it is. • How it works… • Set the first pass from the GreenStar display. • The system will "draw" lines that are parallel to Track 0. • Press a button and AutoTrac will steer your tractor down these parallel lines. • Once you are at the end of the row simply turn the tractor around press the Resume switch and let go of the wheel.
Advantages of GPS in Farming • Benefits of GPS steering of tractors: • More comfortable for the operator. • Reduce overlap, saving $ on fertilizers, pesticides, seeds, etc. • Speed - cover more acres with fewer hours of operation • Tractor traffic on field is in fewer places. • GPS can also be used to tell your farm equipment what to plant, to avoid rocks and other obstacles, and probably other things too.
OnStar • With more than two million subscribers, OnStar is the leading provider of telematics services in the United States. • Telematics is the transmission of data communications between systems and devices. • OnStar's in-vehicle safety, security, and information services use Global Positioning System (GPS) satellite and cellular technology to link the vehicle and driver to the OnStar Center. • At the OnStar Center, advisors offer real-time, personalized help 24 hours a day, 365 days a year. • Some of OnStar’s services: • Automatic Notification of Air Bag DeploymentIn the event that your front air bags deploy, your vehicle automatically sends a signal to OnStar and an Advisor will attempt to contact you in the vehicle. If you do not respond, the Advisor will automatically contact a nearby emergency services provider with your vehicle location. • Emergency ServicesIn an emergency, push the red OnStar emergency button and we can quickly contact a nearby emergency service provider with your location and request for help. • Stolen Vehicle Location AssistanceRoadside Assistance – Whether you need gas, a tire changed, or your car towed, an OnStar Advisor can contact help on your behalf. • Remote Horn And LightsOnStar can flash your exterior lights and sound your horn if you are having trouble locating your vehicle. • Local Traffic and Weather • Driving Directions – Get directions to your destination without having to pull off the road and ask. • Information – Call for restaurant recommendations, hotel locations, and more.
GPS Related Curriculum Outcomes • Early and Middle years GPS related outcomes (K-8): • S-203 Select and use appropriate tools and technologies to accomplish tasks. • S-205 Construct maps that include a title, legend, compass rose, scale, and latitude and longitude. • S-207 Use latitude and longitude to locate and describe places on maps and globes. • S-208 Orient themselves by observing the landscape, using traditional knowledge, or using a compass or other tools and technologies. • (Wording from grade 6 curriculum) • GPS is also ICT – huge chunks of the continuum can be targeted through one GPS project.
Some GPS Project Ideas • Map the colony. Collect data to calculate area, perimeter, distance. • Scavenger hunt / geocaching. • Find examples of… and mark them on the GPS. • Track your field trip. • How many outcomes can you target with a GPS activity? (Social Studies, Math, Phys Ed, ICT, ELA, Science, Art)
