By Cody, Darren, and Katie

• 24 satellites with a minimum of 21 operating 98% of the time

• 6 Orbital planes • visible for

approximately 5 hours above the horizon

• As few as 4 and as many as 12 in “view” at any time, any place

The basic principle behind the technology that makes GPS tracking work is the ancient practice of triangulation. Triangulation is very simply the use of two visual landmarks to calculate one’s position on a given plane. As long as the observer knows the actual distance between the two objects, then they may anticipate their location by making themselves the third angle of a triangle. GPS takes this concept and uses a device like your cell phone or car and uses satellites as the landmarks. Based on how far the signal is away from the satellite’s relative position in the sky, a computer can figure the location of the device giving off the signal to within a few feet.

•x, y, z are the positions we are trying to locate •T = the time error at the receiver •xs, ys, zs are the satellite positions (calculated •Es = a sum of all the modeling errors considered by the GPS •(include tropospheric and ionospheric errors, clock errors from the satellite and any other error the GPS receivers thinks is significant enough to model) •Prs is the approximate (pseudo-range) distance from the receiver to the satellite

2 2 2

s s sPrs T Es x x y y z z

A vehicle tracking system is an electronic device installed in a vehicle to enable the owner or a third party to track the vehicle's location

Cell phone tracking is used in many occasions. Its used to track kids if they run away…like Erik Trevino. Cops use it to trace calls from “wanted” people.

http://education.uncc.edu/droyster/talks/NCTM_2003/NCTM%202003_files/frame.html

http://imageatlas.globexplorer.com/ImageAtlas/view.do

http://www. trimble.com/gps/gpswork-track.shtml

gpsgate.com/