Expedition Menu
1. Welcome
2. The Idea
3. Boarding
4. Ship Tour
5. Back Deck
6. Preparing to Depart
7. Leaving
8. Meeting
9. Bay-Delta-Estuary
10. Navigating
11. The Survey
12. First Data
13. The Mosaic
14. Visualizing
15. Hazards
16. Disposal Site
17. Sediment Map
18. Compare
19. Future Studies
20. Final Meeting
Contact
Don Reed
Dept. of Geology
San José State
University
Map image modified from a USGS map
we want follow in order to get to the start of our survey. It should
not take long, only 20 minutes or so, to get to the starting point
for our survey. Making accurate maps depends on our ability to precisely
locate the ship every few seconds. To do this, we will use the Global
Positioning System or GPS.
The GPS system is based on a network, known as a constellation, of satellites above the Earth. These satellites are in geostationary orbits, meaning that they orbit with the Earth, in order to keep the roughly same position above the Earth at all times. Radio signals are sent from each and every satellite that can be received by the navigation system on our ship. If we can determine the time it takes for the radio signal to go from each satellite to the ship, then we can determine the distance from each satellite to ship. If we know the
distances from at least four satellites, then we can determine our position very precisely – within a few meters (1 meter = 3.3
feet).
We have
reached the starting point for our survey and you are on watch!