Class 17: Introduction to NAVSTAR GPS

19 March 2007

Topics for today• Exam Review

• Deadline for article reviews 6 April 2007

• Some relevant history

• System components– Space– Ground– User

Brahe and Kepler

1546-1601

1571-1630

Kepler’s Laws1. Planetary orbits are elliptical with Sun as one focus.

2. Due to 1 planetary velocities vary. But sweep equal area in equal time.

3. The ratio of the squares of the revolutionary periods for two planets is equal to the ratio of the cubes of their semi-major axes.

Yet more graphics

Post WW-II Radio Navigation

• LORAN

• SHORAN

• OMEGA (ended 1997)

Federal Radionavigation Plan

• http://www.navcen.uscg.gov/pubs/frp2005/2005%20FRP%20WEB.pdf

Doppler

Early SatNav Systems

Transit on left, Timation on right

Radio Navigation

http://www.thespacereview.com/article/626/1

Six Planes/Five Slots

Broadcast Ephemeris Message

GPS Block IIR

Resources

• http://www.colorado.edu/geography/gcraft/notes/gps/gps_f.html

Observation File

SP3 Precise Orbit file

Position for TXSN

Between 1997 and May 2006 the position of this site changed by 0.143 m!

WHAT???????