Have you considered WWVB? Works fine within structures.
Even though the carrier today is phase modulated one can probably glean
1 ms accuracy from it or the data transmitted.
Regards
Brian
On 7/23/2013 14:05, Magnus Danielson wrote:
On 23/07/13 05:55, Jim Lux wrote:
On 7/21/13 6:42 PM, Chri
On 7/22/13 6:30 AM, Tom Van Baak wrote:
For what it's worth, the application is a radar that detects
buried victims in disaster rubble, so the data we are collecting is
basically heartbeats and breathing. the "when was the data taken"
is a "where were we when the data was collected" need. The "
> For what it's worth, the application is a radar that detects buried
> victims in disaster rubble, so the data we are collecting is basically
> heartbeats and breathing. the "when was the data taken" is a "where
> were we when the data was collected" need. The "sync" requirement comes
> from
On 23/07/13 05:55, Jim Lux wrote:
On 7/21/13 6:42 PM, Chris Albertson wrote:
I think the way to keep the sensors in sync is to use the same method
they use to keep cell towers in sync. Basically each tower has a GPS
receiver and also a good local oscillator. The GPS disciplines the
oscillator an
On 7/23/13 4:51 AM, Scott McGrath wrote:
Thanks Jim
Was not aware that <10 Ghz signals could penetrate so deeply. I work for a
enterprise wifi company on the RF side and one of our key challenges is signal
attenuation/distortion by building materials
Any pointers to papers on this?
there's
Thanks Jim
Was not aware that <10 Ghz signals could penetrate so deeply. I work for a
enterprise wifi company on the RF side and one of our key challenges is signal
attenuation/distortion by building materials
Any pointers to papers on this?
I did know that /tvb was using seismic sensors but
On 7/22/13 10:39 AM, Scott McGrath wrote:
Moles are a bit small it would probably work better for woodchucks. who are in
the process of undermining all lawns in neighborhood now.
In a more serious vein most ground penetrating radar is low frequency and I was
not aware that THz waves could pen
On 7/22/13 5:48 AM, Scott McGrath wrote:
You might want to look at what these guys have done for 40 years or so.
Www.geophysical.com
ground penetrating radar doesn't work very well in the typical disaster
rubble enviroment which has uneven surfaces and a lot of random
scattering in the medium
On 7/21/13 6:42 PM, Chris Albertson wrote:
I think the way to keep the sensors in sync is to use the same method
they use to keep cell towers in sync. Basically each tower has a GPS
receiver and also a good local oscillator. The GPS disciplines the
oscillator and the timing is taken from that o
You might want to look at what these guys have done for 40 years or so.
Www.geophysical.com
They have the ability to embed GPS coordinates while recording.
Sent from my iPhone
On Jul 21, 2013, at 4:55 PM, Jim Lux wrote:
> On 7/21/13 1:35 PM, Tom Van Baak wrote:
>>> when I'm in a GPS denied e
I think the way to keep the sensors in sync is to use the same method
they use to keep cell towers in sync. Basically each tower has a GPS
receiver and also a good local oscillator. The GPS disciplines the
oscillator and the timing is taken from that oscillator, not directly
from the GPS. If the
Moles are a bit small it would probably work better for woodchucks. who are in
the process of undermining all lawns in neighborhood now.
In a more serious vein most ground penetrating radar is low frequency and I was
not aware that THz waves could penetrate ground more than a few CM
Scott
Sen
>
>
> Of course all this from the guy who once tried to use seismic sensors and
> GPSDO to triangulate moles in his backyard...
>
>
I don't recall seeing that on leapsecond.com... Sounds like something that
could become an obsession that rivaled clocks in cost. I'm picturing Bill
Murray and a Cad
On 7/21/13 1:35 PM, Tom Van Baak wrote:
when I'm in a GPS denied environment, it's not just because we're
indoors, it's because we're somewhere that GPS isn't available, so
what I'm really doing is providing a sort of flywheel to keep my
little modules synced with each other. I don't need super
> when I'm in a GPS denied environment, it's not just because we're
> indoors, it's because we're somewhere that GPS isn't available, so what
> I'm really doing is providing a sort of flywheel to keep my little
> modules synced with each other. I don't need super accuracy in an
> absolute sens
On 7/21/13 9:28 AM, David J Taylor wrote:
From: Jim Lux
[]
Oh, I didn't actually think it would be 10% off.. more like a few ppm,
depending on temperature. I was wondering more what would happen if you
were indoors for a couple days, then went back out, what the box does.
realistically, I don't
From: Jim Lux
[]
Oh, I didn't actually think it would be 10% off.. more like a few ppm,
depending on temperature. I was wondering more what would happen if you
were indoors for a couple days, then went back out, what the box does.
realistically, I don't expect that it smoothly brings it back into
On 7/21/13 6:59 AM, David J Taylor wrote:
My own notes on the GPS-18 LVC are here:
http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm
You may be able to gather something about the electrical characteristics
from that note - the device will happily feed to PC "RS-232" ports
connected in parallel
On 7/21/13 7:15 AM, David McGaw wrote:
The GPS-18 does NOT output 1PPS until it acquires lock. Then the 1PPS
stays on even if lock is lost, running from the internal crystal. I
have not checked, but once it reacquires lock I presume it jumps to the
correct second. All outputs including 1PPS ar
The GPS-18 does NOT output 1PPS until it acquires lock. Then the 1PPS
stays on even if lock is lost, running from the internal crystal. I
have not checked, but once it reacquires lock I presume it jumps to the
correct second. All outputs including 1PPS are CMOS levels, so it
drives both low
I don't have a GPS-18 in front of me, and I'm modifying some software
remotely, and I ran across an issue that someone on this list probably
knows off the top of their head.
Does the GPS-18 put out 1pps pulses even if it hasn't got a fix yet?
That is, when you apply power, does it just start putt
I don't have a GPS-18 in front of me, and I'm modifying some software
remotely, and I ran across an issue that someone on this list probably
knows off the top of their head.
Does the GPS-18 put out 1pps pulses even if it hasn't got a fix yet?
That is, when you apply power, does it just start p
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