1. GPS
Doug Van Zee

2. Global Positioning System
The Global Positioning System is the most significant development in navigation since the compass.
A network of satellites that continuously transmit coded information, which makes it possible to precisely identify locations on Earth by measuring distance from the satellites.

3. Global Positioning System
Control segment: 5 ground stations tracking satellite positions, keeping the satellites in their proper orbits, and telling the satellites their exact positions and the exact time.
Space segment: 24 satellites (21 working 3 spares).
User segment: GPS receiver including a radio receiver, quartz clock, memory and a CPU to perform a wide variety of calculations.

4. GPS Signal Radio signals at 50 watt transmission power
Travel line of sight only, i.e. through clouds and glass, but not mountains and buildings.

5. Space Segment 24 satellites cruising at an altitude of 13, 670 miles
6 orbits with 4 satellites each
Two complete orbits in 24 hours
2000 lbs, 17 feet in diameter, solar powered
Expected lifetime 10 years
Any location on earth will have line of sight access to a minimum of six satellites at all times

6. How it works Velocity X Travel Time = Distance
It takes at least 4 satellites to obtain a three-dimensional position fix
Velocity X Travel Time = Distance
Triangulation
1st satellite -> sphere x
2nd satellite -> circle
3rd satellite -> 2 points
4th satellite -> 1 point

7. GPS errors Ionosphere and troposphere delays
Number of satellites visible
Before 2000, there was an intentional degradation of satellite signal
Was turned off May 1st, 2000 (Operation Desert Storm)
Allowed 10 times the accuracy for civilians

8. User Segment GPS receiver (parallel multi-channel) Time of day
Location (lat and long)
Waypoints Define: marked location
Routes
Distances
Tracks
Maps
PC connectivity

9. Geocaching Hi-tech version of treasure hunting
Caches typically consist of a waterproof container discreetly placed within the local terrain. The container will include a logbook and any number of more or less valuable items such as toys, books, money, jewelry, trinkets, etc.
Rules:
fill out the logbook
take something out of the cache
put something in the cache
return the cache to the exact position and condition in which it was found
Information about geocaching and the location of caches can be found at