[time-nuts] GPS Modules Indoors

[David J Taylor]

Greetings

I know that the accuracy of GPS degrades indoors. However, suppose
that I just want to turn a GPS module on, acquire the current time
accurate to a second, and then turn it off. I can get a good deal on
the U-Blox LEA-5H modules (same as used on Arduino shields I think),
which have a high sensitivity, and I can use an active antenna if
needed.

Am I wasting my time. Sorry for not requiring the time more accurate
than a second, but that's all the clients require.

Tom Harris
=========================================================

Tom,

If the GPS has a battery backup, then you might get re-acquisition within 
less than 30 seconds of powering up.  That's approximate with a u-blox 
NEO-6M on the top floor of a two-storey building, about 1/3 the way into the 
room, so most of the signal is through the roof.

Without battery backup, the acquisition time might be a lot longer (15-20 
minutes), or even worse (hours) with a different GPS module which needs a 
much stronger signal to acquire than to track.  The one which took hours had 
a 15 mm square patch antenna (AdaFruit), versus the 25 mm square antenna on 
the u-blox board I had.

The two units I am comparing are shown on my Web page here:

  http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html

although it's down right now.  I quite accpet that other folks may have 
different results (or if "indoors" is next to a window!).

Cheers,
David
-- 
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor at blueyonder.co.uk