Flight Planning and Navigation GPS Navigation © 2011 Project Lead The Way, Inc.Aerospace Engineering

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

Satellite Precision One satellite limits possible GPS receiver location to a spherical location Two satellites limit possible GPS receiver location to a circular location

Satellite Precision Simplified diagram One location is impossible due to location and speed Three satellites limit possible GPS receiver location to two locations

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

GPS Orbital Configuration Track Across the Earth

GPS Accuracy Within 100 meters (328 ft) –Original GPS Within 15 m (49 ft) –Selective availability removed 3-5 m (10-16 ft) –Differential position (GDPS) < 3 m (10 ft) –Wide Area Augmentation System (WAAS)

GDOP - Geometric Dilution of Precision

GPS Augmentations Systems to increase GPS accuracy –Nationwide Differential GPS System (NDGPS) –Wide Area Augmentation System (WAAS) –Continuously Operating Reference Station (CORS) –Global Differential GPS (GDGPS) –International GNSS Service (IGS)

NDGPS – Nationwide Differential GPS System Accurately surveyed locations used for reference Corrects GPS for increased accuracy for users on land and water Developing system for cm accuracy

WAAS - Wide Area Augmentation System Operated by FAA (U.S. Federal Aviation Administration) Aircraft navigation for all phases of flight

Benefits of WAAS Primary means of navigation More direct routes Approach with vertical guidance Decommission older equipment Simplify onboard equipment Increased capacity

References Federal Aviation Administration (2009). Retrieved from iStockphoto (2011). Retrieved from woman-using-a-gps.php National Aeronautics and Space Administration (2009). Retrieved from National Coordination Office for Space-Based Positioning, Navigation, and Timing (2013). Retrieved from