The Global Positioning System (GPS)

1. The Global Positioning System (GPS) ENGR097S.168 College of Engineering Penn State Christine Fogas Jeremy Hall Mercedes Hill Zachary Leuschner Nicholas Plate Mindy Sanchez

2. What is GPS? • GPS stands for “Global Positioning System” and is a system in which signals from satellites are sent to receivers on Earth • Based on the signal’s arrival time, the distance can then be calculated which then reveals the receiver’s position • This produces an effective way of determining the position of a receiver at any location on Earth.

3. A Deeper Look at GPS • History of the system • Use in the military • Commercial use in vehicles • Use in areas of the sciences (weather patterns, seafloor mapping, etc.) • Possible flaws of the system

4. Timeline • United States Government • The Cold War • 1960’s Science Revolution • The Leaders • Military Branches • Aerospace Corporation • NAVSEG • Organization of Military Branches • Developed the predominant and current system.

5. Results • Vectors, anyone? • Constellation of 27 Satellites • Accuracy • Within 2 cm • Now a small concern • Future Developments • Private and public market • New amenities and features

6. Military Applications • The military has become dependent on GPS • The military uses GPS in the following areas: • Vehicle Navigation • Precision Weapon Guidance • Tracking • It has changed the way the US wages war, and it has become necessary for ships, aircraft, vehicles, and soldiers • Dependence has led to the importance to protect GPS from jamming

7. Military Applications: Weapon Guidance • A recent GPS technology that uses both weapons and tracking (weapon guidance) is infrared trajectory correction fuze based GPS and accurate exploding-point control • Infrared trajectory correction fuze based GPS and accurate exploding-point control uses GPS as a receiver of the ammunition data from the infrared imaging detector to give an exact position to the exploding point control system • This process corrects the trajectory paths so that it locates and accurately hits the target • The purpose of this is to cause minimal collateral damage

8. Military Applications: Interference Protection • In the military, it is important to recognize strengths and weaknesses • GPS is needed to continue effective warfare, but it is vulnerable to jamming • Military has taken action • Devices that find the location of the interference are being created • The purpose of this device is to stop the interference so that the military can continue to use GPS and jam the opponent's signal • One example is the Location of GPS Interferers (LOCO GPSI)‏ • It scans quickly to for anything that would jam a signal

9. GPS Navigation System in Vehicles GPS has become a huge part of how we navigate in vehicles. The GPS was designed in cars to make them more safe and easier to operate. The GPS helps not only contribute to direct navigations but the quality of the vehicle to make for safer navigations.

10. The Components The typical GPS unit consists of a space segment, a control segment, and a user segment. Each component contributes to how the GPS works. The space segment is a constellation of two dozen satellites orbiting the earth twice every 24 hours, clocking at approximately 10,900 nautical miles above the earth's surface, which helps approximate certain locations.

11. GPS Calculations and Satellites In cars, GPS systems are generally quite accurate but the accuracy depends on how fast the reference receivers broadcast their signals. Slow signals throw off the accuracy of the GPS. When a GPS is installed in a vehicle it can calculate the exact location of the vehicle and the speed at which it vehicle is traveling. GPS can give alternate routes and calculate a certain time it takes to reach a destination based on the current traveling speed. In order to effectively reach a specific destination the driver enters it into the GPS database. After a destination is recorded in the GPS, the satellite orbiting around the earth sends a signal to the GPS and calculates a route. The signal that the GPS sends calculates a route to the specific destination.

12. GPS Used to Monitor Car Condition GPS systems can also record driving activity, including the addresses, states and streets of past destinations. Some GPS systems in cars even issue warnings when the car has a reached an unsafe speed. The condition of a car can also be calculated and monitored by GPS technology. GPS systems can issue warnings when the battery is low or an oil change is needed. Recently, Ford has developed a new system through GPS on the Ford Focus that will alert emergency services when an airbag deploys. This system has emergency procedures for locating the vehicle quickly and providing help for drivers or passengers who may have become injured in a crash.

13. GPS Rate of Change GPS is one of the most frequently and effectively used components in vehicles with modern-day technology. GPS technology in vehicles is advancing very rapidly and has become an important method of over-land navigation. Although GPS units aren’t perfect in performance, new models are being developed and problems with the older ones are being fixed.

14. GPS Technology • Applications in the field of general science and engineering: • GPS technology is available to a huge community worldwide because the positioning signal is broadcasted virtually everywhere due to many satellites. With so many different applications of this growing technology, the community of GPS users is constantly expanding. Various GPS satellites orbiting earth

15. GPS Technology (cont’d.) • GPS technology can be used to monitor the weather: • CORS (“Continually Operating Reference Stations”)  more than 1,100 GPS-receiving stations positioned throughout North America, Mexico, and Central America. • Receive continuously transmitted radio signals. CORS data, combined with aerial photography, is used to achieve greater GPS accuracy and reliability. • CORS data can be used to monitor moisture in the atmosphere  enables severe weather predictions to take place. • GPS technology helps the nation’s infrastructure: • GPS data helps regional planners to determine how to improve traffic flow, merge construction with existing utility systems, protect the public from natural disasters, etc. • GPS is also essential for exact positioning of transportation, utility, energy, and communications systems.

16. GPS Technology (cont’d.) • GPS technology is greatly utilized in navigation: • Land, sea, or air • Convenient, reliable, and safer • Airport obstruction charts  improved airport safety • Marine: underwater surveying (marine seismic surveying and seafloor mapping), buoy placement, sweeping, dredging, and navigational hazard location and mapping • GPS also very useful to commercial fishing fleets • Search and Rescue Operations more successful with GPS • Due to advancements in the basic GPS signal, known as Differential GPS (DGPS), greater safety and precision can be achieved over water. • Electronic Chart Display and Information Systems are gradually replacing paper nautical charts and changing the way mariners navigate at sea. • Safer harbors, ports, and seaways

17. Multipath Error When the signals from the satellites take different paths to reach receiver Leads for the signal to take longer to reach receiver Leads to inaccuracy

18. Corrections for Error Advancing technology in signal processing Specialized Antenna involving polarizations Separating direct (good) signals from reflected (bad) signals

19. Clock Errors • The instrumental error present in atomic clocks on GPS satellite • Time Relativity • The stronger the field of gravitation, the slower time moves • The GPS satellite is in weaker field, so time seems to move faster on satellite

20. Correction for Errors More precise clocks in receivers and satellites Programming corrections for time dilations

21. Final Thoughts • Although there are still flaws in the system, the GPS has already grown to be an almost essential part of today’s society.