[time-nuts] GPS, USGS Early Earthquake Warning

Magnus Danielson magnus at rubidium.dyndns.org
Sat Apr 28 15:27:06 UTC 2012


On 04/28/2012 02:39 AM, Hal Murray wrote:
>
>> The quake talk was not on line so I watched the one on Climate Change and
>> it's impact on N. California.  Interesting,  but no human impact data, only
>> wildlife.
>
> It's up now.
>    http://online.wr.usgs.gov/calendar/2012/apr12.html
>
> For a good time sink, my favorite talk was March 2011:
>    Unraveling the Mystery of Avian Navigation
>    http://online.wr.usgs.gov/calendar/2011/mar11.html
> A little more text back at:
>    http://online.wr.usgs.gov/calendar/2011.html
>
> For anybody in the Silicon Valley area, their open house is May 19-20.  It's kid friendly, both big kids and little kids.  You get to talk to the people who are actually doing the work.  They are happy with geeky questions.
>
> -------------
>
> Back to somewhat time-nutty stuff...
>
> Does anybody understand how they are using GPS and/or have performance numbers?
>
> They don't need the actual position (DC), just the changes in position.  They need it now.  They can't wait for post processing.  I'm not sure how much accuracy they need.  I'd guess in the cm range.
>
> (Maybe I can learn more at the open house.)

Extract the ECEF position, build a long term average position. Subtract 
each given position with the known ECEF average, square the differences, 
sum and square root to get an RMS value... set a threshold for 
trigger... whenever the difference RMS is above threashold start 
reporting. Keeping a memory of previous diffs will get a pre-trigger memory.

Not too hard, given good antenna and carrier phase, preferably double 
frequency reciever.

Cheers,
Magnus



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