Re: Help with cellphone GPS

"mcbridms" <u32709@uwe> wrote in news:6f9359b022c81@uwe:

> Also, does anyone
> know how effective/if at all the GPS system would be on a ski mountain
(I
> understand you need 3-4 towers to provide a location, but is there any
> technology that can be used with cellphones that would gaurantee a GPS
> connection at all times? Anyone that can enlighten me??? PLEASE
HELP!!!
> Thanks!
>

The GPS doesn't "use the towers", other than to transfer data from the
phone. A GPS receiver built into the phone produced the lat/long of the
phone...IF the phone can see enough GPS satellites to produce a fix.
(Read that outdoors or in an open area with windows.) The GPS data, time
stamped, is transmitted as data through the cellular system to the
government bureaucrats so you can be forcibly tracked, if "they" so
desire.

Should work great outdoors on a ski slope. You get one fix every 60
seconds, not continuously. GPS is, by nature, quite SLOW in responding.
Once you've walked into a building, the GPS data stops and the cops know
which door you went into on that last fix. It isn't rocket science. If
you handheld little Garmin road warrior GPS doesn't read, your cellphone
doesn't either. GPS is in the low microwave region and is line of sight
to the sky to LEO (low earth orbit) satellites running N to S to N
overhead. Most modern receivers copy 12 satellites at once, putting a
fix at about 3 feet in consumer products...close enough for government
work....(c;

Easily within range of government agents' 9mm weapons.

Larry
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At 22 Mar 2007 22:02:49 +0000 Larry wrote:

> The GPS doesn't "use the towers", other than to transfer data from the
> phone.

Depends on the phone, Larry. While CDMA phones use a tower-assisted
satellite GPS system for E911 compliance, GSM phones just use the towers
(and are a bit less accurate.)

> A GPS receiver built into the phone produced the lat/long of the
> phone...IF the phone can see enough GPS satellites to produce a fix.

Again, even CDMA phones use a tower-assisted system. Often the phones do
not do the actual lat/lon calculations, but simply relay the raw GPS data
to the tower and the calculations are done by the carrier. From what I
understand, they can fallback on pure tower triangulation as well when
sat data is unavailable. (Remember, the Feds require that te E911
location works 95% of the time. A pure satellite-only solution would be
worthless for a phone left indoors for an extended period of time.)

The advantages of this system are two-fold (for the carrier): since the
phone isn't really the GPS- it just has a GPS radio receiver- it needs
less computational horsepower and consumes less battery power, and more
importantly, the phone doesn't know where it is, so any GPS software
applications must use carrier-supplied data, and therefore can't bypass
any carrier-imposed fees or restrictions. After all, what's the point of
Verizon selling businesses a $30-50/month/user tracking system if a third
party could program the phone to read and transmit it's own data to offer
a similar service for $20? ;-)

> (Read that outdoors or in an open area with windows.) The GPS data,
time
> stamped, is transmitted as data through the cellular system to the
> government bureaucrats so you can be forcibly tracked, if "they" so
> desire.

Oh for love of Pete, it's a f***ing safety feature and can be turned off
by the user (except if 911 is called, then location data is sent
regardless of user preference.)


> Should work great outdoors on a ski slope. You get one fix every 60
> seconds, not continuously. GPS is, by nature, quite SLOW in responding.

My satellite-based GPS receiver gives 1-second updates. Plenty fast
enough for in-car navigation- I suspect it could handle skiing.

> Once you've walked into a building, the GPS data stops and the cops
know
> which door you went into on that last fix. It isn't rocket science.
If
> you handheld little Garmin road warrior GPS doesn't read, your
cellphone
> doesn't either.

Yes, it does, by triangulation, but with less accuracy.