QHY 174 GPS Calibration LED issue // USB Traffic weirdness

andyho
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by andyho »

Robin,

Thanks for confirming. But my computer differed by just a few seconds from UTC. SharpCap threw the "BadData" error, and got hung. To get unstuck, I adjusted the Windows time by "synchronizing with internet time." Upon doing this, SharpCap instantaneously went to "PartialData," followed a few minutes later by "Locked."

This has happened several times before. I must emphasize that at no time did my computer's clock differ by more than a few seconds from UTC.

I don't understand the purpose of the +/- 1 day (86400 sec) comparison, as one would think that GPS time supersedes Windows clock time. As you know, there's even a button that permits syncing the Windows clock to the camera's time after Lock is achieved.

Perhaps there could be an option to skip checking that the Windows clock agrees to within +/-1 day. Or perhaps do away with it altogether.

Andy Howell

P.S. On reflection, maybe the intent is to do a quality check of time stamp data from the camera during a run. Nevertheless, this quality check can be a "show stopper" at startup.
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admin
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by admin »

Hi Andy,

yes, the intention is the quality check of GPS data - on some cameras it throws those bad timestamps in on random frames and the idea is to avoid writing something that is obviously wrong to output file.

It might be a good idea if you turn on the GPS logging option in SharpCap to try to capture what is happening when you see bad data - this logs the GPS data from every frame to a CSV file so we can go back and examine exactly what came from the camera and how it was processed - see https://docs.sharpcap.co.uk/4.0/#GPS%20Logging

cheers,

Robin
andyho
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by andyho »

Robin,

I've been saving the GPS log file for some time now. Attached is a graph of System-GPS(s) versus Sequence Number from several nights ago. The camera showed a large positive difference at start up, which caused BadData. The only way I could shake the camera out of this state was to sync the Windows computer with "internet time" (i.e., the NTP server polled by Windows). Doing so was followed instantaneously by "PartialData", and several minutes later by "Locked."
_System-GPS v. Sequence Number.png
_System-GPS v. Sequence Number.png (68.75 KiB) Viewed 53 times
Lesson Learned: Sync the computer's clock to "internet time" (or some other NTP server) before launching SharpCap.

This worked last night. Camera started up with immediate lock on GPS.
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by admin »

Hi,

good that you have a way to get it working, although I can't quite work out how it would work like that - the GPS date/time data is extracted directly from the binary encoded in the start of the image and comes from the camera direct to SharpCap. As far as I know the camera has no idea what the windows time is... Weird :)

cheers,

Robin
procyon12
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by procyon12 »

Hello Andy and Robin, all,
As far as I know the camera has no idea what the windows time is... Weird :)
From my experience I can confirm this. I think that "Bad Data" at camera start depends on a bad GPS system condition (antenna, connections, almanac, ...) and possibly also on bad SC (initial) settings.

Cheers,

Christian
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