Author Topic: GPS Signal Lost  (Read 2422 times)

Gary Nelson

GPS Signal Lost
« on: April 05, 2021, 08:07:54 pm »
Since flying resumed last week, I keep getting “GPS Signal Lost”. This seems more likely pre take-off,  but even when flying it still happens more often than not. If I have my iPhone and iPad simultaneously running SD using “Use PilotAware” they will both show “GPS Signal Lost”.  I can still hear the PAW audio warnings via PAW audio-out plumbed into my radio. If I then revert to use the iPad or iPhone internal GPS i.e. “Use Location Services” it works 100% of time but obviously SD then no longer shows other traffic.

Any clues anyone? The only thing I can think that has changed is software upgrades to SD, iPhone and iPad?




iPad mini 5         IOS14.4.1
iPhone 12           IOS14.4.2
PAW classic        20200906
SD - iPad           3.15.1
SD - iPhone        3.15.1.295
FLARM                7.01
« Last Edit: April 08, 2021, 01:58:33 pm by Gary Nelson »

steveu

Re: GPS Signal Lost
« Reply #1 on: April 05, 2021, 08:46:16 pm »
How close is any of the other devices to the PAW GPS antenna? I've had Bluetooth and FLARM disturbing GPS lock on another project... Some tablets are poor for EMC and can swamp the front end of a GPS antenna...

Is it worth checking the GPS antenna is properly seated if you are using an internal one, inside the PAW case if it's a Rosetta, or that the extension cable to the GPS external antenna is properly seated if external?

exfirepro

Re: GPS Signal Lost
« Reply #2 on: April 05, 2021, 10:42:43 pm »
Hi Gary,

I hope this isn’t another case of deja-vue, though this time SD is definitively advising that it is a GPS issue rather than a connectivity issue. I don’t suppose you managed to check your PAW Home Screen to establish if it had actually lost GPS fix? Can you please remind us what GPS you are using and where your PAW is fitted (presumably we are talking Eurostar).

My iPad Mini 5 has been running iPadOS 14.4.1 but has literally just notified me that it wants to update to iPadOS 14.4.2. I will allow it to do so and give it a run with the latest SkyDemon 3.15.1.295 tomorrow (not able to fly though I’m afraid as we aren’t allowed to travel outside our local authority area up here yet).

Your PilotAware also needs to be updated to 20201101 (though I can’t remember off hand what the changes are). You should be able to update via the PilotAware Firmware Updater App (now available on Android as well as Apple).

Regards

Peter

Gary Nelson

Re: GPS Signal Lost
« Reply #3 on: April 06, 2021, 12:45:00 am »
Thanks Steveu and Peter - I will upgrade and check the points you both mentioned and report back - the GPS is the one that PAW supply that connects by a cable to the PAW unit. I did wonder if the connection had worked loose - on my Eurostar it is a 50 or so screw panel that I have to undo to get access to check

exfirepro

Re: GPS Signal Lost
« Reply #4 on: April 06, 2021, 09:03:14 am »
Gary,

I’ve just been reading back through all the previous connectivity issues threads to remind myself of all the issues we had with the iOS updates. Although I’m pretty sure this isn’t a ‘connectivity’ issue this time, can you check that SkyDemon is showing and enabled in Settings/Privacy/Local Network on both your devices and let me know. (For others reading this - this only applies to latest iOS 14 versions, it doesn’t appear on older iPads/phones running earlier versions of iOS).

Regards

Peter

Gary Nelson

Re: GPS Signal Lost
« Reply #5 on: April 08, 2021, 01:56:19 pm »
1.    I attach a snapshot of my PAW home screen. This was taken yesterday, just when SD was hanging with the "GPS Signal Lost" message . I can see the bottom line GPS signal on the attached
       snapshot is orange and I wonder if that is significant. Is it informing that PAW can see 8 satellites but is only using 3. I would add when running SD using the iPad internal Location Services
      (GPS) it aways always works seamlessly and SD never ever hangs with a "GPS Signal Lost" message, never!
   
2.    Despite the above glitch, which happened just after takeoff, SD using Pilot Aware was more stable yesterday than a few days earlier. On a 40 minute flght it was generally stable but there
       were still about 4 times when it glitched and I got the "GPS Signal Lost".

Rgds

Gary



iPad mini 5         IOS13.7 (will bite the bullet and finally upgrade tonight to 14.4.2)
iPhone 12           IOS14.4.2
PAW classic        20200906   (will upgrade to 20201101 next time at airfield)
SD - iPad           3.15.1.295
SD - iPhone        3.15.1.295
FLARM               7.01
« Last Edit: April 08, 2021, 03:06:08 pm by Gary Nelson »

Admin

Re: GPS Signal Lost
« Reply #6 on: April 08, 2021, 05:47:46 pm »
Hi Gary

There is a newer version than 20200906, this contained a minor fix which I would recommend installing
Pretty easy using the PilotAware installer APP

thx
Lee

Ian Melville

Re: GPS Signal Lost
« Reply #7 on: April 08, 2021, 05:56:57 pm »
Your PilotAware has not had much time to acquire the correct set of satellites.  It has been up for just 5 min. If it has recently had full acquisition then it should be much quicker (sub 1 min). But lack of use and or moving it a fair distance can increase the time. 5 minutes has not been long enough in this case as there is lock on only 3, which is insufficient. I would also expect the time to update as it should be just one hour different(BST) from your phone.

If this happens after only short disconnect, then there could be a problem with the GPS dongle. It may not be holding the data in the flash memory. Leave it plugged into an active USB port for a day or two and see if that makes any difference. The VK-172 has a tiny battery on the u-blox 7 for back-up. Not sure which GPS you have?

AlanG

Re: GPS Signal Lost
« Reply #8 on: April 08, 2021, 07:14:53 pm »
Hi Gary

I started this a couple of hours ago then got diverted to a minor household emergency and of course others have responded meantime.

The iPad/iPhone experts will be back shortly i'm sure but just to conform that you are correct in your reading of the Home screen.  You are indeed only seeing 8 satellites with 3 in use, which is insufficient for a GPS lock.  You need at least 4 in use.
If this shot was taken out in the open, (I think you said you were airborne so presume it is,) then only having 8 in view is a bit surprising, especially if you are referring to the GPS mouse which is available from PilotAware.  I use the basic Ublox 7 from the clasic but on a short USB extender to get it on top of my flexwing pod.  Paw unit is underneath.
with so few satellites in view you will find that the "in use" satellites can flit between 3 & 4, sometimes 5 and back to 3 several times before getting a solid lock especially as Ian says if it has been moved any distance whilst switched off as it needs to find the satellites again.  Whichever GPS you are using it must have a clear unobstructed view of the sky

Regards
Alan

Ian Melville

Re: GPS Signal Lost
« Reply #9 on: April 08, 2021, 08:03:32 pm »
Alan, I assumed Gary was on the ground? QNE of 18feet and the PAW has only been running for 5 minutes

exfirepro

Re: GPS Signal Lost
« Reply #10 on: April 08, 2021, 10:22:20 pm »
Hi Gary / All,

Just catching up on this thread after an enforced absence this afternoon. As the guys have said above, your Home Screen shows only 3 satellites in use - which is insufficient to achieve a GPS fix. Without a solid fix, PilotAware won't transmit and obviously can't pass location data to the Nav system or your transponder.

I appreciate that the unit had only been running for 5 minutes when you took the screenshot, but from pictures you posted previously in an earlier thread (relevant one copied below), I recall that you are (or at least were) using a standard PilotAware GPS Mouse, located up under the front edge of the coaming on the engine side of the firewall. I remember thinking at the time that that didn't look like the ideal position to ensure a good view of the sky for reception of satellites as it must presumably be under the metal skin of the aircraft (unless the panels in this area are fibreglass?). I can certainly see fibreglass underneath the mouse, but it's what's on top, between it and the sky, that is important here. I appreciate that you have been using PilotAware with the GPS in that same location for some time, but I feel this may (at least in part) be contributory to your current issues. I am no expert on Eurostar construction, however, so I would certainly recommend seeking a second opinion from the likes of Paul Kiddell (or others) via the Eurostar Forum. If you do, please let us know what they say.

Best Regards

Peter
« Last Edit: April 09, 2021, 07:56:22 am by exfirepro »

Gary Nelson

Re: GPS Signal Lost
« Reply #11 on: April 14, 2021, 06:42:48 am »
Thanks all and Peter is correct with the photo showing my pilot aware GPS mouse glued under fibreglass. On flights yesterday from Herts to Norfolk Coast (reaching upto 5000 feet) i was still intermittently losing GPS signals. I have the PAW mouse tucked under the fibreglass for aesthetics to keep my cockpit neater but think I will bite the bullet and reposition the mouse inside the cockpit but now on top of the same fibreglass. It will then have same “sky view” as the ipad with its internal GPS (which always works 100%)

Will then report back

exfirepro

Re: GPS Signal Lost
« Reply #12 on: April 14, 2021, 08:19:30 am »
Thanks Gary,

I'm certain that will improve things - and certainly can't make anything worse.

Best Regards

Peter

Gary Nelson

Re: GPS Signal Lost
« Reply #13 on: April 17, 2021, 06:39:35 am »
Flying today and “GPS SIGNAL LOST” message again at 2000 feet, on one of the 5 or so occasions when the pilot aware GPS failed on a 40 minute flight. Before lockdown it was far less flakey. I therefore can’t help thinking software upgrades not hardware are causing this. I have not yet tried moving the pilot aware mouse so it is still positioned underneath the fibreglass that sits on top of the console.


Admin

Re: GPS Signal Lost
« Reply #14 on: April 17, 2021, 07:51:22 am »
Hi Gary
This will be hardware/install specific, if you think about it, a software issue would be seen across every device
The gps lost is caused by a specific message from the gps device indicating invalid data in one of the messages, I think if moving the gps does not solve this, the next step is to try replacing

Out of interesting, this is not coincidental with using the RT ?
We have had reports, some radios on specific frequencies, generate harmonics that interfere with the GPS receivers

Finally could you provide your track file this will report the gps status during usage
Thx
Lee
« Last Edit: April 17, 2021, 07:58:50 am by Admin »