Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.
HOW DOES
GPS
WORK?
THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
GPS is the Global Positioning System,
also called NavStar.
It was built by the US Military and has
been operational since ...
GPS currently has 31 active satellites in
orbits inclined 55 degrees to the
equator.
THE GREEN BERET PREPARATION AND SURVI...
You need 3 GPS satellites for a 2D fix
(i.e. no altitude) or 4 satellites for a 3D
fix.
This could be significant if you a...
The satellites orbit about 20,000
kilometers up and make two orbits per
day. The orbits are designed so that
there are alw...
The GPS receiver gets a signal from
each GPS satellite with the exact time
the signals are sent. By subtracting the
time t...
To calculate the time the GPS signals
took to arrive, the GPS receiver needs
to know the time very accurately. GPS
satelli...
When you switch your GPS on, the time-to-
first-fix depends on how long it is since you
last used the GPS. If the GPS has ...
The accuracy of the position your GPS
reports is influenced by a number of
factors, such as the positions of the
satellite...
Cellphone GPS units get a fix almost
immediately.
They use Assisted GPS (A-GPS) to
improve the time to first fix, and even...
Once you are out cellphone and WiFi
coverage, a cellphone GPS unit has to
rely on the satellites to provide the
ephemeris ...
Things to consider about GPS:
Make sure you have whatever maps
you might need pre-loaded in the
memory in case you can’t d...
Solar Flares can also interfere with the
GPS System.
Commercial planes are required to have
back up navigation to the GPS ...
For information on where to get free
topographic maps and basic map
reading, please use the link below or at
the end to my...
Print
Book
Free downloadable Powerpoint
slideshows on survival, history
writing, and interesting information
is available ...
The guide on the left is a complete preparation and
survival guide. The one on the right is a pocket-size
manual focusing ...
New York Times bestselling author, graduate of West Point, former
Green Beret, and feeder of two yellow Labs, most famousl...
How Does GPS Work? And Why Do You Need To Understand It?
Upcoming SlideShare
Loading in …5
×

How Does GPS Work? And Why Do You Need To Understand It?

20 views

Published on

Understanding how GPS works will give you insight into how effective it is, how accurate and how much you rely on it. Why does your car get your location faster at certain times? How many satellites are there? Does your cell phone GPS need reception for the GPS to work?

Published in: Education
  • Be the first to comment

  • Be the first to like this

How Does GPS Work? And Why Do You Need To Understand It?

  1. 1. HOW DOES GPS WORK? THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
  2. 2. GPS is the Global Positioning System, also called NavStar. It was built by the US Military and has been operational since 1995. Most GPS receivers utilize a combination of both NavStar and the Russian GLONOSS satellites for best results. THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
  3. 3. GPS currently has 31 active satellites in orbits inclined 55 degrees to the equator. THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
  4. 4. You need 3 GPS satellites for a 2D fix (i.e. no altitude) or 4 satellites for a 3D fix. This could be significant if you are in the mountains at higher altitudes, making it less accurate. THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
  5. 5. The satellites orbit about 20,000 kilometers up and make two orbits per day. The orbits are designed so that there are always 6 satellites in range from most places on the earth. THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
  6. 6. The GPS receiver gets a signal from each GPS satellite with the exact time the signals are sent. By subtracting the time the signal was transmitted from the time it was received, the GPS can tell how far it is from each satellite. The receiver knows the exact position in the sky of the satellites. Given the travel time of the GPS signals from three satellites and their exact position, the GPS receiver can determine your position in three dimensions - east-west (longitude), north-south (latitude) and
  7. 7. To calculate the time the GPS signals took to arrive, the GPS receiver needs to know the time very accurately. GPS satellites have atomic clocks that keep precise time, however it's not feasible to equip a GPS receiver with an atomic clock. The GPS receiver uses the signal from satellite to determine the exact time. THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
  8. 8. When you switch your GPS on, the time-to- first-fix depends on how long it is since you last used the GPS. If the GPS has been recently used you should get a fix almost immediately. If it hasn't, put the GPS outside with a clear view of the sky. If you have a GPS in a vehicle, it's better to wait for the unit to get a fix before driving off. Receiving data from a satellite takes 30 seconds. If you drive in an area with tall buildings or other obstructions it may take longer to get the data from four satellites, needed for the first fix.
  9. 9. The accuracy of the position your GPS reports is influenced by a number of factors, such as the positions of the satellites in the sky, atmospheric effects, satellite clock errors, etc. GPS units often show on the screen an accuracy figure. Under ideal conditions, this usually is within 5 meters. THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
  10. 10. Cellphone GPS units get a fix almost immediately. They use Assisted GPS (A-GPS) to improve the time to first fix, and even allow a fix in conditions where the GPS might not otherwise be able to function. THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
  11. 11. Once you are out cellphone and WiFi coverage, a cellphone GPS unit has to rely on the satellites to provide the ephemeris & almanac date so, like a standard recreational GPS, it takes a minute or so to get a fix from a cold start. THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
  12. 12. Things to consider about GPS: Make sure you have whatever maps you might need pre-loaded in the memory in case you can’t download them. Remember, GPS works only as long as the power works. It also only works as long as the satellites are transmitting. Always back up with paper maps and know how to navigate THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
  13. 13. Solar Flares can also interfere with the GPS System. Commercial planes are required to have back up navigation to the GPS system. THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
  14. 14. For information on where to get free topographic maps and basic map reading, please use the link below or at the end to my other survival slideshares. THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
  15. 15. Print Book Free downloadable Powerpoint slideshows on survival, history writing, and interesting information is available HERE THE GREEN BERET PREPARATION AND SURVIVAL GUIDE
  16. 16. The guide on the left is a complete preparation and survival guide. The one on the right is a pocket-size manual focusing on survival essentials. SURVIVAL GUIDES
  17. 17. New York Times bestselling author, graduate of West Point, former Green Beret, and feeder of two yellow Labs, most famously Cool Gus. He’s had over 75 books published, including the #1 bestselling series Time Patrol, Area 51, Atlantis, and the Green Berets. Born in the Bronx and having traveled the world he now lives peacefully with his wife and labs. Sort of. Free books below available HERE www.bobmayer.com

×