Flight Planning and NavigationGPS Navigation

© 2011 Project Lead The Way, Inc.Aerospace Engineering

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

Satellite Precision

One satellitelimits possible GPS receiver location to a spherical location

Two satelliteslimit possible GPS receiver location to a circular location

Satellite Precision

Simplifieddiagram

One location is impossible due to location and speed

Three satelliteslimit 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 10-15 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 http://www.faa.gov/

iStockphoto (2011). Retrieved from http://www.istockphoto.com/stock-photo-5975040-woman-using-a-gps.php

National Aeronautics and Space Administration (2009). Retrieved from http://www.nasa.gov/

National Coordination Office for Space-Based Positioning, Navigation, and Timing (2013). Retrieved from http://www.gps.gov/