nospam <nospam@nospam.invalid> wrote in news:120620081711330002%
nospam@nospam.invalid:
> it doesn't 'require' it, but if there's a cell signal available, some
> of the info that would normally be sent from the gps satellites can be
> more reliably obtained from the cell towers, thereby dramatically
> reducing the time to obtain a fix and/or maintaining a fix in weak
> signal conditions.
>
>
Totally false, a fantasy.
The GPS system is ANALOG, based on precise TIMING and the phase
relationship between the pulses generated by the birds and the physical
position of the receiver antenna.
GPS depends on having a DIRECT, unobstructed view from the receiver's
antenna to the maximum number of satellites over the horizon. Come see
the birds' positions:
http://science.nasa.gov/Realtime/jtr.../JTrack3D.html
Jtrack is a realtime Java app showing the exact location of every
satellite, dead or alive, orbiting the planet. Click and DRAG on it and
you'll move it in 3 dimensions. Click on one of the dots and Jtrack will
tell you what that bird's name and number is and draw you a 3D track of
its orbit.
Now, you'll notice very close to the earth, right on the edge of the
atmosphere, a cloud of LEO (low earth orbit) satellites like MIR and ISS
and the Shuttle if it's orbiting the earth and the Hubble Space Telescope
(close to the earth so it can be turned around to point at the planet for
fantastic optical spying they won't let you see.) Way out in a ring
directly over the plane of the equator are your geosynchronous satellites
for DTV, communications, DISH network and the tv systems across the
planet around 32,800 miles altitude...FAR FAR AWAY from anything Shuttle
is capable of visiting...the reason there's no repair missions.
Now, look at the cloud of birds about halfway in between these two orbit
clusters. I say cloud because they are all in very high angle orbits to
cover the polar regions and are very high in altitude so they remain over
your optical/radio horizon for very long periods of times because of
their high altitudes. Start clicking on these birds and you'll find a
group of military spy satellites, constellations of high polar
communications birds and the GPS system birds. When you find a GPS bird
in its constellation, note its very high altitude and very high angle
orbit, in relation to the equatorial rotation of the planet. This
insures there are many of the 24 birds in the constellation over the
horizon at any one time. It also makes sure there can be a few outages
with no appreciable change in GPS fix accuracy if we lose a few. This
orbit also makes it very hard for opposition countries to shoot them down
so far up....in spite of what the TV media says.
The exact position of every bird is very accurately known. Each bird
provides very accurate timing pulses from its cesium-beam frequency
standards fed to it from the ground, even with very accurate clock
timing. But, from WAY UP THERE, there ISN'T GOING TO BE ANY WAY for ANY
sellphone, even iPhones!!!, to receive a GPS signal through RF opaque
objects like BUILDINGS or WALLS or SHEET STEEL ROOF PLATES or even a
thick canopy of TREES, which absorb what tiny bit of RF that falls on
your spot on the planet surface into the noise....
THIS is why Sellphone GPS simply isn't going to work in your pocket
anywhere you happen to be.....THAT IS A PURE FANTASY!
Technical Specs of iPhone 3G posted
Linear Mode
