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'[EE] Cell phones, GPS and cost'
2007\09\13@161015 by Matthew Mucker

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4) You could have a pressure sensor to determine roughly when the plane took
off and is landing
----- Original Message -----
From: "Cedric Chang" <spam_OUTccTakeThisOuTspamnope9.com>
To: "Microcontroller discussion list - Public." <.....piclistKILLspamspam@spam@mit.edu>
Sent: Thursday, September 13, 2007 2:52 PM
Subject: [EE]: Cell phones, GPS and cost


{Quote hidden}

> --

2007\09\13@163635 by limor

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> > 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 ?

hmm, well, are you sure that you will be able to get GPS readings from
inside the (metal encased) hold of an airplane? :) maybe just shut off
while in the hold by doing a (tcp/ip-like) retry backoff. no signal?
try again in 10 minutes, then 30, then an hour. etc.

alternately, most modern GPS units can tell you the altitude, i know
the lassen does...ymmv on how accurate this is and whether it works at
high altitudes and in planes.

 limor

2007\09\13@164457 by Robert Rolf

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LIGHT? The cargo hold is always dark during flight.
Even at night, unloading uses lights, and the cargo belts are illuminated.
Just remember that your package can have ANY orientation so you'll need more
than one sensor.

Lack of RF? Inside the hold you have a faraday cage. NO RF.
Outside, there will be all kinds of aircraft band radio signals (navigation
aides being most likely for commercial aircraft).

Robert

Matthew Mucker wrote:

> 4) You could have a pressure sensor to determine roughly when the plane took
> off and is landing
> {Original Message removed}

2007\09\13@164744 by Carl Denk

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We have had Lowrance Expedition and airmap GPS's, they report altitude
less than +/- 50 foot , more like 30 foot difference than the aircraft's
certified altimeter, IFR certified GPS, or know ground elevation. When
driving changes in elevation like going uphill seem smooth in 10 foot
increments.

limor wrote:
{Quote hidden}

2007\09\13@171331 by Carl Denk

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Altimeter won't work in pressurized aircraft, they usually maintain a
maximum altitude of around 8000' at cruise, and the plane could land at
an airport higher that that. How are you shipping? Most carriers like
Fedex, UPS have excellent tracking. If you can't trust your carrier,
maybe time to rethink that. For movement, many aircraft GPS's use
exceeding a set speed to log takeoff and landing times, say use 60 MPH
(100Kph) as a speed. Very unlikely a plane is going to be doing that
without intention of taking to the air, and in the air that speed,
except for a very few planes will be too slow.  For a metal skinned (and
maybe carbon fiber composite) airplane the GPS antenna is located
outside topside. For fiberglass and fabric skinned, an antenna inside
generally works.

Robert Rolf wrote:
{Quote hidden}

>> {Original Message removed}

2007\09\13@184757 by Cedric Chang

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>
> On Sep 13, 2007, at 2:35 PM, limor wrote:
>
>>> 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 ?
>
> hmm, well, are you sure that you will be able to get GPS readings from
> inside the (metal encased) hold of an airplane? :) maybe just shut off
> while in the hold by doing a (tcp/ip-like) retry backoff. no signal?
> try again in 10 minutes, then 30, then an hour. etc.
>
> alternately, most modern GPS units can tell you the altitude, i know
> the lassen does...ymmv on how accurate this is and whether it works at
> high altitudes and in planes.
>
>   limor

I thought GPS would be suppressed inside a metal airplane.   I  
wondered if the plane issues any kind of RF signature.
Cedric

2007\09\14@012948 by William \Chops\ Westfield

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>> 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.

You know, for about $25/month, Disney will sell you a cell phone and
rate plan that includes the ability to determine the location of the
phone from their web site...
http://disneymobile.go.com/disneymobile/home.do

BillW

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