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GPS signal on Saturday 6th of April 2019 ?

MustangPhil

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Hello, has any of you have an idea on the Rollever GPS Week effects on the Anafi ?
This will occure during a Saturday... when I intend to fly... but not at 23:59 ! Is it safe to fly on Sunday ?
I read that the count of weeks can be changed on firmware updates, do you think Parrot did implement that ? (Should I ask them ?)
Thanks for your feedbacks,
Phil

———

If you haven’t heard of the GPS Week Rollover and its potentially critical consequences, or haven’t taken any action, now it is the time to do so, and you can do it by reading this article. Due to this GPS event and its effects, explained hereinafter, EGNOS encourages all its users to check their GPS receivers.

The GPS Week Number Rollover Event

Among other data, GPS broadcast the date and time information in a specific format, consisting of the current week and the current number of seconds in the week. However, the length of the week number field is 10-bit and consequently it is limited to a range of 0 to 1023, or 1024 total weeks (a 19.7 year epoch). The week number is referenced to the start of the GPS Time Epoch, and at the end of week 1023, the week number restarts from 0 (“rollover”) and a new GPS Time Epoch is defined.

With the GPS starting on the 6 January 1980, the first reset of the 1024 weeks counter happened on 21 August 1999, ending the initial GPS Time Epoch. The next reset of the week counter from 1023 to zero will be on Saturday 6 April 2019, at 23:59:42 UTC (note that there is currently an 18-second gap between UTC Time and GPS Time), ending the second GPS Time.

Critical after effects and what you should do

On Saturday 6 April 2019 the behavior of an erroneous GPS receiver may vary: from providing incorrect date/time information (e.g. incorrect UTC Time due to failure on the GPS Time-to-UTC conversion algorithm) to leading up to the complete failure of the receiver. Also be aware that some manufactures implement the week number referenced to a date different than 6 January 1980 (e.g. the firmware date is used as reference). These devices would not be affected by the GPS Week Rollover on the 6 April 2019, but rather the problem would occur on a different date.

In summary, a wrong handling of this event may cause adverse effects, and therefore we suggest following these actions1 as a proactive measure:

To check that the firmware installed on your GPS receiver(s) is up-to-date.
To contact the GPS receiver manufacturer in order to ensure the readiness for the event.
To test the devices in a GPS Week Rollover simulated environment (e.g. a GPS simulator).
If you are not able to confirm that your GPS receiver is not impacted by the rollover, you should assume its possible failure and take into consideration the appropriate mitigation measures.
 
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MustangPhil

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Thanks for this link.
I’ll do what he suggested (do not trust the manufacturer and do your own tests).
I’ll adapt my preflight checklist for this specific Saturday-Sunday flight:

- Switch on my phone first and check my GPS position is the actual one on a map app (google Maps or equivalent independently from Parrot’s Apps).
- Switch on the Anafi on a clear space ‘in view of GPS’, wait 10 minutes before any flight to give it time to update GPS infos.
- Connect the SC3 with the phone, and get in FF6 to check if Anafi GPS count is Ok (not just ‘green’ now we have this possibility in the App but at least 10 GPS)
- Check the Anafi GPS position and my phone-SC3 position on the map provided by FF6 to see if they are coherent.

This simple test should be enough to fly safely...
 

Krusty Geeza

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Thanks for this link.
I’ll do what he suggested (do not trust the manufacturer and do your own tests).
I’ll adapt my preflight checklist for this specific Saturday-Sunday flight:

- Switch on my phone first and check my GPS position is the actual one on a map app (google Maps or equivalent independently from Parrot’s Apps).
- Switch on the Anafi on a clear space ‘in view of GPS’, wait 10 minutes before any flight to give it time to update GPS infos.
- Connect the SC3 with the phone, and get in FF6 to check if Anafi GPS count is Ok (not just ‘green’ now we have this possibility in the App but at least 10 GPS)
- Check the Anafi GPS position and my phone-SC3 position on the map provided by FF6 to see if they are coherent.

This simple test should be enough to fly safely...
Phil, thanks for writing the steps out, I was too busy to do it tonight, unfortunately. That should be of benefit to many others out there! (y)
 
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Landbo

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I have one of Garmin's very first handheld GPS unit. The last time there was rollover, it seemed like nothing had happened and I expect that to continue.

I also find it difficult to see what could happen since the date is of no importance to the GPS unit finding its position. But we can only wait and see if there are mess in the engine room !!!

Regards, Leif.
 

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