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'[EE]: Cell phones, GPS and cost'
2007\09\13@155216 by Cedric Chang

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Greetings

I have been asked to come up with a GPS unit that can track items  
that are shipped via airplane and report the location via cell  
phone.  Probably the best time to get a GPS fix is during the time  
the items are off-loaded and on-loaded.

1)  Is cell phone technology the best bet ?   Would SMS be a good  
choice ?
2)  My research indicates that GSM is the most popular cell phone  
protocol.  Is this true ?
3)  GSM modems appear to be very expensive.  I am considering try to  
get a cell phone from China that is stripped down to the features I  
want.  Any recommendations about how I should proceed ?
4) To manage power I want to shut off the unit while in flight.  Is  
there any kind of signal that aircraft emit that I could use to  
determine that the unit is in an aircraft ?

Thanks

Cedric

2007\09\13@165425 by Herbert Graf

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On Thu, 2007-09-13 at 13:52 -0600, Cedric Chang wrote:
> Greetings
>
> I have been asked to come up with a GPS unit that can track items  
> that are shipped via airplane and report the location via cell  
> phone.  Probably the best time to get a GPS fix is during the time  
> the items are off-loaded and on-loaded.
>
> 1)  Is cell phone technology the best bet ?   Would SMS be a good  
> choice ?

I think it would be a good choice.

> 2)  My research indicates that GSM is the most popular cell phone  
> protocol.  Is this true ?

Yes, by far GSM is the most common. However, note the frequencies aren't
the same the world over. North America (and a few other places) have two
GSM bands: 850 and 1900MHz. Everywhere else has 900MHz and 1800MHz
bands. The good thing is many devices are available in "quad band"
config these days, so if you choose the right module you should be OK.

> 3)  GSM modems appear to be very expensive.  I am considering try to  
> get a cell phone from China that is stripped down to the features I  
> want.  Any recommendations about how I should proceed ?
> 4) To manage power I want to shut off the unit while in flight.  Is  
> there any kind of signal that aircraft emit that I could use to  
> determine that the unit is in an aircraft ?

400Hz. AFAIK most planes use 400Hz for onboard board (less iron needed
for transformers, so lighter). I don't know how hard it would be to
detect this 400Hz though. TTYL

2007\09\13@172153 by Recon

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This is maybe stretching things a bit, but I think you will get the idea

Has it occurred to you that the FAA, Homeland Security and other foreign
security agencies would probably not want such a device anywhere near an
airplane. They have all kinds of equipment looking for devices similar
to this that may be used to trigger bombs.  When they found such a
device they would pull the package to inspect it , there by delaying the
package.

Recon

Cedric Chang wrote:

{Quote hidden}

2007\09\13@173053 by Eoin Ross

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Apart from the issues of having to turn off GPS and cell phones at all times during flights (At least on passenger craft and freight does go on passenger 747s....

I would say:

1) altitude (Pressure sensor - look for about 8000ft)
2) sustained G reading in a straight line for a set time (Accelerometer - Take off)  

or a combination of the two - turn off phone under 8000 ft when accelerating for 30 seconds
turn on the phone when a landing detected - jolt or accelleration matching a landing. This would be trickier the better the pilot was.

>>> spam_OUTccTakeThisOuTspamnope9.com 13 Sep 07 15:52:04 >>>
Greetings

I have been asked to come up with a GPS unit that can track items  
that are shipped via airplane and report the location via cell  
phone.  Probably the best time to get a GPS fix is during the time  
the items are off-loaded and on-loaded.

1)  Is cell phone technology the best bet ?   Would SMS be a good  
choice ?
2)  My research indicates that GSM is the most popular cell phone  
protocol.  Is this true ?
3)  GSM modems appear to be very expensive.  I am considering try to  
get a cell phone from China that is stripped down to the features I  
want.  Any recommendations about how I should proceed ?
4) To manage power I want to shut off the unit while in flight.  Is  
there any kind of signal that aircraft emit that I could use to  
determine that the unit is in an aircraft ?

Thanks

Cedric

2007\09\13@184933 by Cedric Chang

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{Quote hidden}

Not my problem.   I will pass your comments on.
Cedric
{Quote hidden}

> --

2007\09\13@220521 by Dr Skip

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I have seen unintentional radiators interfere with instrumentation
onboard aircraft, and it's a subject that makes flight crews jittery.
That is emission from an active electronic device, not even a formal
transmitter. Most of the recommendations involving acceleration or light
could be reproduced by dropping or cargo compartment lights on, etc., so
it wouldn't be reliable.

The liability would be enormous, and potentially for the engineer as
well, should one of these cause an in-flight accident or such, even from
just coming awake and probing for signal. A more subtle liability would
be getting tagged as someone to be 'watched' by Feds because of your
surreptitious technology meant to detect air travel...;) Of course once
the press was out on it, the client might not be around long to pay for
the development anymore.... One way or another, it may well be your problem!

Any in-flight shutdown would have to be foolproof and non-modifiable.

Skip

Cedric Chang wrote:
>
> Not my problem.   I will pass your comments on.
> Cedric
>  

2007\09\14@040145 by KPL

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Isn't just scanning for GPS availability enough? If signal from
satellites is not available, item possibly is already loaded into
aircraft. Even if it is not there, without signal it can sleep anyway.
Wake after some 10 minutes to check again.

Do not switch gsm module on, if it is not really needed.
GPS receiver alone shuld not make such a big interference to make
problems for aircraft electronics?

--
KPL

2007\09\14@044946 by Dave King

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GPS and cell phones can cause rather severe errors on ils systems.
I didn't think they would until I saw the dept of transport getting
15-20 degrees of error on a ils glideslope. That's more than enough
to miss things and end up having a bad day. In flight they don't
seem to effect anything but on precision approaches they are not
very welcome.

Dave

{Original Message removed}

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