Except for the WAAS satellites
(https://en.wikipedia.org/wiki/Wide_Area_Augmentation_System).
bp
<part15sbs{at}gmail{dot}com>
On 8/11/2015 5:20 PM, Mike Hammett wrote:
GPS isn't geosynchronous.
-----
Mike Hammett
Intelligent Computing Solutions
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<https://www.facebook.com/ICSIL><https://plus.google.com/+IntelligentComputingSolutionsDeKalb><https://www.linkedin.com/company/intelligent-computing-solutions><https://twitter.com/ICSIL>
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------------------------------------------------------------------------
*From: *"Jaime Solorza" <losguyswirel...@gmail.com>
*To: *"Animal Farm" <af@afmug.com>
*Sent: *Tuesday, August 11, 2015 5:54:49 PM
*Subject: *Re: [AFMUG] GPS Timing
Hum ? So geosynchronous is just a suggestion?
On Aug 11, 2015 12:25 PM, "Sean Heskett" <af...@zirkel.us
<mailto:af...@zirkel.us>> wrote:
the satellites are constantly moving tho and since they are moving
faster in orbit than we are here on earth you need to account for
relativity. knowing where you are doesn't give you enough
information to know where the satellite is and therefore you
can't accurately calculate the relativity offset. once you have
3D lock with 4 satellites you can accurately calculate the
relativity offset and therefore calculate the accurate time for
where you are on earth.
shoulda taken the blue pill ;-)
-Sean
On Tue, Aug 11, 2015 at 12:08 PM, Bill Prince <part15...@gmail.com
<mailto:part15...@gmail.com>> wrote:
That's what I thought too. Once one of these little beggars
has been online for a half hour or more, the location should
be "set" so to speak. I would then expect them to hold time
sync even with 1 satellite in view. Knowing that the location
is static and unmoving, I would expect that maintaining time
lock would be gravy.
Sadly, this does not seem to be the case.
bp
<part15sbs{at}gmail{dot}com>
On 8/11/2015 10:48 AM, Chuck McCown wrote:
Interesting, I guess you need to know where you are to
calculate the delay. Had not considered that. But if you
know where you are and have ephermis data, you should be
able to calculate the delay and arrive at a pretty
accurate timing pulse with one satellite.
*From:* Forrest Christian (List Account)
<mailto:li...@packetflux.com>
*Sent:* Tuesday, August 11, 2015 11:39 AM
*To:* af <mailto:af@afmug.com>
*Subject:* Re: [AFMUG] GPS Timing
You need an accurate 3d position to get accurate
timing. To have an accurate 3d position using GPS alone,
you need four satellites. Three only gets you a 2d lock,
and less than that you don't get a lock at all.
There are receivers out there which will survey a position
and then use that position to be able to continue to
provide a timing signal if you subsequently lose lock but
still have sats in view. As far as I know, this type of
receiver is not in use in any commercially available
timing product for the cambium radios. In fact I think
we've almost all ended up using the exact same GPS
modules, at least for any recently designed product.
Some of the earlier products would attempt to preserve the
sync signal across a GPS lock loss with various levels of
success. For instance the cmm micro in early releases
provided a wildly incorrect sync pulse even without a
lock. Same with early syncpipes. The CTM has a holdover
timer. And so on. I think most of us have moved away
from this in newer designs.
On Aug 11, 2015 8:36 AM, "Dan Petermann" <d...@wyoming.com
<mailto:d...@wyoming.com>> wrote:
What is the minimum amount of satellites needed for a
proper GPS sync pulse?
And does that differ across products (CMM, CTM,
SyncPipe, etc.)?
