User`s manual

27
How does GPS work?
A GPS satellite orbits the Earth at an altitude of a little over 12,000 miles and travels almost 9,000
miles per hour. It completes an orbit about twice a day. It transmits data that indicates its location
and the current time. All GPS satellites synchronize operations so that these repeating signals are
transmitted at the same instant. The signals, moving at the speed of light, arrive at our GPS receiver
at slightly different times because some satellites are farther away than others. The distance to the
GPS satellites can be determined by estimating the amount of time it takes for their signals to reach
our Device.
How Many Satellites Do We Use?
There are between 24–30 satellites in operation orbiting on 6 different axes at any given time. It
takes at least 3 different satellites to calculate a position. With an unobstructed view, our Device can
be seen and receive a signal from up to 12 satellites at the same time.
How Accurate is GPS?
Our Device has been known to give a location of within a few feet. Generally, it will give a location
within 10–20 yards. The more satellites that can see the Device the better the accuracy will be.
Satellites Acquired: (0-2 no current signal, 3-6 lowest accuracy, 7–9 medium accuracy, 10–12 highest
accuracy).
Are There False Readings?
Yes, it is not uncommon to receive a false reading from time to time. A false reading can be the result
of obstructions such as (i) being inside homes, schools or buildings; (ii) locations in urban areas
between large buildings; (iii) locations in hilly or mountainous areas; (iv) locations around military
bases or government installations; and (v) natural occurring phenomena such as electromagnetic or
solar events.
What is a GPS Bounce?
GPS bounce is also known as multipath. Multipath results when the direct path to your receiver is
blocked (by your body, your house, roof, trees, mountains, buildings, etc) and the signal from the
satellite is REFLECTED by some object. The reflecting surface may be: buildings, mountains, the
ground, or any object that happens to be a radio reflector at 1.6Ghz. Multipath are radio signals which
have traveled FURTHER to get to your receiver than they should have. This can result in your GPS
miscalculating its position because the signals may have traveled from feet to miles further to get to
you than the path of a direct line of sight signal.
How Do We Get An Address for Latitude and Longitude?
We take the latitude and longitude and use publically available mapping systems like Google and
MapQuest to calculate the addresses that are shown on our tracking server.
GPS for Beginners