GPS - Aircraft Navigation

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THIS DAY IN AVIATION December 2 1949 — Civil Aeronautics Board approves transcontinental coach service by American Airlines with Douglas DC-6 equipment.

THIS DAY IN AVIATION December 2 1949 — North American Aviation delivers YF-86D prototype, a swept-back to jet fighter, to Muroc Air Force Base, California.

THIS DAY IN AVIATION December 2 1949 — United States Navy reveals details on Allison Division's XT-40 turbo-prop engine, which will power the Navy's Convair XP5Y-1 Flying Boat. The XT-40 has a rating of 5,500 hp without increase in fuel consumption rate.

THIS DAY IN AVIATION December 2 1976 — The Boeing 747 SCA, an ex-American Airlines airliner which has been adapted to carry the United States Space Shuttle, makes its first flight.

THIS DAY IN AVIATION December 2 1986 — A “Concorde” SST airliner carrying 94 passengers returns to Charles de Gaulle airport after an 18-day round-the- world journey; total flying time amounted to 31 hours 51 minutes.

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December 2016 27 28 Chapter 9 Navigation 29 30 Review Chapter 9 Test 1 SUNDAY MONDAY TUESDAY WEDNESDAY THURSDAY FRIDAY SATURDAY 27 28 Chapter 9 Navigation 29 30 Review Chapter 9 Test 1 GEO CACHE Navigation 2 3   4 5 Chapter 6 Advances in Aeronautics 6 7 Chapter 6 Test 8 Flight Line Friday Thursday Edition 9 Patriots Point Field Trip 10 11 12 Chapter 17 Aviation Careers 13 14 15 Savannah Tech Field Trip 16 Chapter 21 Rocket Fundamentals 17 18 19 20 Chapter 21 Test 21 Rocket Launch 22 ½ Day VACATION BEGINS 23 HOLIDAY 24

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GPS – Aircraft Navigation You are an aircraft pilot who must navigate a course from “waypoint” to “waypoint” in sequence and locate all items. Your team will plot a course of 5 “waypoint items” and document their location with lat/long coordinates. You will create a map of your routes in sequence. (in Powerpoint and take pictures of your items/location with coordinates) Selective Availability was the military degradation of the GPS accuracy for defense purposes. More information is available at the National Executive Committee for Space-Based PNT website: http://pnt.gov/public/sa/ The PRC and ephemeris signals from four satellites should provide an absolutely accurate position to the precision of the atomic clock on the satellite. The key word is “should” as there are many problems associated with timing the signal’s travel time. Remember even a thousandth of a second is a huge error!   Problems include the reduction in the speed of light as it enters the atmosphere (error to greater distance), signals that reflect off of multiple objects and create echoes that arrive at different times, purposeful errors, and even atomic clock errors. We can correct for the atmospheric problems by using more advanced technology. If the receiver can monitor dual frequencies, then it can compare the amount of variation between a low-frequency (slowed more) and a high-frequency (slowed less) signal to deduce the error and correct for it. The GPS system broadcasts on two different carrier frequencies called L1 and L2. Unfortunately, this requires a very sophisticated receiver. Only the military has access to the L2 carrier channel. The other option is to build in atmospheric models so that “typical” corrections can be made to all incoming signals. Receivers can deal with the multi-path errors by employing signal rejection analysis software. The basic principle is that the first signal to arrive will have traveled along the shortest route and thus any signal that arrives later is most likely an echo and should be ignored. Before May 1, 2000, the government purposely degraded the timing data of the satellite’s clock by adding noise to the signal. They may also have introduced slight inaccuracies to the ephemeris data. Military GPS receivers made use of a decryption key to obtain the full accuracy information. This Selective Availability (SA) was disabled, which improved the accuracy of GPS positions by a factor of 10. All of these errors combined introduced errors of about 10 meters. With SA active, this led to errors of hundreds of feet. Without SA the basic GPS receiver is capable of measuring positions to within 30 or 50 feet. This is accurate enough for an aircraft approaching a runway, but unfortunately it isn’t accurate enough to land the aircraft on the centerline of the runway.

GPS – Aircraft Navigation You will be provided a entry log to record all items and their respective lat/long coordinates Teams will exchange coordinate charts with item description. Final report will be Powerpoint with pictures of waypoint locations and items and complete conclusion questions on worksheet from website Selective Availability was the military degradation of the GPS accuracy for defense purposes. More information is available at the National Executive Committee for Space-Based PNT website: http://pnt.gov/public/sa/ The PRC and ephemeris signals from four satellites should provide an absolutely accurate position to the precision of the atomic clock on the satellite. The key word is “should” as there are many problems associated with timing the signal’s travel time. Remember even a thousandth of a second is a huge error!   Problems include the reduction in the speed of light as it enters the atmosphere (error to greater distance), signals that reflect off of multiple objects and create echoes that arrive at different times, purposeful errors, and even atomic clock errors. We can correct for the atmospheric problems by using more advanced technology. If the receiver can monitor dual frequencies, then it can compare the amount of variation between a low-frequency (slowed more) and a high-frequency (slowed less) signal to deduce the error and correct for it. The GPS system broadcasts on two different carrier frequencies called L1 and L2. Unfortunately, this requires a very sophisticated receiver. Only the military has access to the L2 carrier channel. The other option is to build in atmospheric models so that “typical” corrections can be made to all incoming signals. Receivers can deal with the multi-path errors by employing signal rejection analysis software. The basic principle is that the first signal to arrive will have traveled along the shortest route and thus any signal that arrives later is most likely an echo and should be ignored. Before May 1, 2000, the government purposely degraded the timing data of the satellite’s clock by adding noise to the signal. They may also have introduced slight inaccuracies to the ephemeris data. Military GPS receivers made use of a decryption key to obtain the full accuracy information. This Selective Availability (SA) was disabled, which improved the accuracy of GPS positions by a factor of 10. All of these errors combined introduced errors of about 10 meters. With SA active, this led to errors of hundreds of feet. Without SA the basic GPS receiver is capable of measuring positions to within 30 or 50 feet. This is accurate enough for an aircraft approaching a runway, but unfortunately it isn’t accurate enough to land the aircraft on the centerline of the runway.

GARMIN – eTrex GPS

LAT / LONG FORMAT

How to Record Data

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GEO CACHE MAPPING GOOGLE EARTH

Global Positioning System (GPS)

Global Positioning System (GPS) Cloud of 24 GPS satellites orbit the Earth Satellite positions are accurately known GPS device receives satellite signal with ‘time-sent’ information Device calculates distance to satellite Intersection point of multiple satellites defines device location Image source: http://scign.jpl.nasa.gov/learn/gps2.htm A global positioning system utilizes multiple satellites that orbit the Earth. The triangulation of the satellites is based on extremely precise timing of radio waves that are received from the satellites. Since the satellites are not stationary but moving through space at thousands of miles per hour, the radio waves are slow. They bend and bounce their way from satellite to receiver. With the challenges that arise from the satellites orbiting the Earth, it is easier to examine how the GPS works in smaller bits. How does GPS really work, how is the accuracy challenged and maintained, and how are technical and engineering techniques used to overcome those challenges to make GPS the most readily available, accurate, and truly global navigational system available?

GPS Orbital Configuration 24 satellites 20,000 km (Approximately 12,500 mi) above Earth Orbits take 12 hours Cover entire Earth

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