1. UNIT 4 – MODULE 1: Global Positioning System (GPS)

2. INTRO TO GPS Provides users with navigation, position and time, in all weather conditions, anywhere on Earth. Achieved through a constellation of satellites in Medium Earth Orbit (MEO). The entire GPS is called the NAVigation Statellite Timing And Radar (NAVSTAR).

3. HISTORY OF GPS 1974 – First of many GPS satellites launched into space. 1983 – President Ronald Reagan orders the GPS to be made public for civilian use. 1994 – Constellation of 24 satellites completed. 2000 – Full GPS signal quality becomes available for civilian use. 2005 – First of several second-generation satellites launched. 2017 (Est.) – First of several third-generation satellites to be launched. *

4. GPS MANAGEMENT The entire system is managed by the U.S. Air Force. Master control station located at Shriever Air Force Base in Colorado. Performs atmospheric corrections to the military GPS service for improved accuracy. Credit: U.S. Air Force

5. CONTROL SEGMENT Master Control Station (MCS) Ground Antennas Monitor Stations – Air Force – Alternate MCS – Remote Tracking – National Geospatial- Intelligence Agency (NGA) Credit: www.gps.gov

6. GPS SATELLITES At least 24 required to maintain global coverage. 32 currently in orbit to ensure any losses are immediately covered. Four or more operate in six different orbital planes (MEO). Credit: Wikipedia/El pak Credit: Penn State

7. GPS SATELLITES (Continued) Revolve around Earth ~ every 12 hours (twice a day). Have an altitude of 20,200 km (12,550 miles). Always sending out radio signals. We know where they are at all times.

8. HOW GPS WORKS Measures the time it takes a radio signal (from a satellite) to reach a ground receiver. Radio signal travels at the speed of light (300,000 km/s). It’s a fixed speed. The GPS receiver on the ground notes the signal’s exact arrival time, and uses to calculate its distance from each satellite signal. Credit: Gawler Wheelers

9. HOW GPS WORKS (Continued) Once the receiver knows its distance from each satellite, it can determine location. The information contained within a GPS signal includes: – Precise Time – Location – Status Credit: University of Colorado - Boulder

10. TRILATERATION Positioning from three distances. GPS receivers use trilateration for determining position via signal calculations from three satellites. Three satellites identify position and a fourth is used for increased accuracy. Credit: BBC *

11. ATOMIC CLOCKS Synchronize time for our technology. Most precise time keeper that’s built into every GPS satellite. Accurate to within 100 billionth of a second. Precise time needed for communications, power grids, finance networks, etc. Credit: University of Alaska - Fairbanks

12. GPS ERROR Can result from a number of sources: – Tall Buildings – Atmospheric Effects – GPS Receiver Clock Signal acquisition also limited when underground or underwater. Credit: Berkeley Lab Credit: NASA *

13. GPS RECEIVERS Different types of GPS receivers (e.g. handheld, vehicle). Most handheld are waterproof, have a battery life of 15+ hours, and are equipped with a barometer, compass and altimeter. Smartphones can act as GPS receivers, but have many limitations. Credit: Wessex Archaeology Credit: www.trimble.com

14. GPS RECEIVERS (Continued) GPS receivers for the car have several capabilities: – Various Map Displays – Step-by-Step Directions – Real-Time Traffic Updates & Alternate Route Suggestions – Identify Nearby Amenities (e.g. Gas Station, Tourist Attractions, Restaurants) Credit: blog.autointhebox.com Credit: http://www.imgneed.com

15. GPS SIGNALS Four signals available for civilian use: – L1C/A – L1C – L2C – L5 Restricted signals for military use: – P Code – M Code Credit: Mina Shin

16. APPLICATIONS: AGRICULTURE Farm Planning Field Mapping – Boundaries – Irrigation Systems – Problem Areas (e.g. weeds, disease) Soil Sampling Tractor Guidance Crop Scouting Credit: UC Davis *

17. APPLICATIONS: AVIATION Real-Time, Accurate Positioning Information Enhanced Route Selection Increased Safety (Air & Ground) Reduced Delays Credit: http://www.stephan-schwab.com *

18. APPLICATIONS: EARTHQUAKES When used with sensors, GPS can be used to evaluate & predict earthquakes. Allows for the precise measurement of elevation changes, land tilt and horizontal movement along fault lines. Credit: Scripps Institution of Oceanography *

19. APPLICATIONS: ENVIRONMENT Pattern Identification Disaster Tracking Wildlife Preservation Enhanced/In-Depth Analyses for Assessing Environmental Issues Resource Management Credit: NOAA Credit: www.gps.gov

20. APPLICATIONS: OUTDOOR ACTIVITIES Provides highly-accurate weather positioning information. Reduces chances of getting lost in remote areas. Many activities can involve GPS: – Skiers – Runners & Cyclists – Hiking & Mountain Climbing Credit: www.pacsafe.com Credit: www.garmin.com

21. APPLICATIONS: ROADS & HIGHWAYS Increased Safety & Mobility Improved Monitoring of Traffic Conditions Reduced Road Surveying Costs Enhanced Logistics Credit: Wei Fang/Getty Images

22. APPLICATIONS: SURVEYING & MAPPING More Accurate/Reliable Data Acquisition Reduced Operational Limitations Enhanced Productivity: – Time – Labor – Equipment Credit: Leica Geosystems

23. APPLICATIONS: TIME Global Access to Atomic Clock Time Synchronization is necessary for highly critical infrastructure: – Communications – Power Grids – Financial Systems Credit: Casio