[time-nuts] Fw: Skytraq / GPS Almanac

Tom Van Baak tvb at LeapSecond.com
Tue Sep 26 18:20:30 EDT 2017

An interesting note from Said, below...
I've sent a couple of queries out to GPS professionals.
Feel free to comment if you have concrete information that would help.
Also, if during the past week any of you were logging almanacs or continuously recording the 50 bps raw data from any GPS/SV, please let me know.


From: "Said Jackson" <saidjack at jackson-labs.com>
Sent: Tuesday, September 26, 2017 12:07 PM

> Tom,
> Not sure if you have heard of the recent changes to the GPS Almanac causing
> issues with the Skytraq receivers. This has apparently happened around 9/20.
> We have received word from Skytraq that units operating in ROM mode (3D
> Mobile mode) are affected, but not units using the Position Hold/Auto Survey
> Flash mode, and units that are presently running will continue to run well.
> Units operating in 3D Mobile mode that are reset or power-cycled will not be
> able to achieve a GPS Fix. This is a now verified bug in the Skytraq ROM
> firmware.
> Just to re-iterate the above: units operated in Auto Survey - Position Hold
> mode are not affected at all by this.
> We are working on a patch for this for users that need to run the units in
> 3D Mobile mode, and hope to have one in the next few days. This patch will
> have to be applied here at JLT, so units will have to be returned here once
> the patch is available.
> In the meantime units that are powered-on and operating properly should be
> left powered-on, or switched to Position Hold mode (but the switch must be
> made while power is removed from the board!)
> This is very unfortunate, and we are very sorry for the inconvenience this
> might be causing users. Apparently this is likely affecting all ROM-operated
> Skytraq receivers. Not good.
> In parallel we are also trying to reach the GPSOC to determine why the
> parameter switch was done, and if they can please revert back to the old
> setting which apparently had been used for decades until last week.
> Please let me know if you have heard additional reports or info, and please
> feel free to post the above info on Time Nuts.
> Bye,
> Said

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