On 05/23/2011 07:24 PM, Phil Vandry wrote:
> On Wed, May 18, 2011 at 03:19:16PM +0200, Eric Smith wrote:
>> Main application here is in a sea shipping container.
>> The key issues are RF communication (when in a GSM range of course) 
>> and power management due to the long haul journey including journey 
>> overland. Power supply has to be in the form of an additional battery.
>> Technical issue is to have minimal size OS and to be low in power
>> consumption.  And robust.
> If you sleep and only wake up at intervals, you should anticipate some
> difficulty acquiring a GPS signal every time you wake up. The GPS in
> the Freerunner is really designed to make use of A-GPS and if you can't
> do it because you are at sea and far from any network signal, it can
> take a long time to get a position. We have sometimes seen it take over
> 40 minutes to get a good fix (unit mounted on an aircraft glareshield).
> -Phil
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You could overcome the TTFF problem by using the agps software from [1]
It loads the needed data from the gps chip and uses that the next time
you power on the gps unit.
I usually get a fix in 2 minutes.
If you send the log data to a server via GPRS, you might want to use
rsync with the --inplace option.
The logs will only grow i suspect and i use this method of transferring
the gps log from my car to my server at home,
while driving.
It also helps to chop the log files in smaller parts (+/- 2Mb per file)
in case the GPRS connection is not that reliable, a resend
will take less time.
Roaming data can be expensive, so you might want to look at that too,
with your mobile phone provider.

Good luck with your project, and keep us posted about the
successes/failures, we would like to learn from it.

Kind regards,

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