On 6/10/2021 5:39 PM, Alan Walls wrote:
Recently I had a couple of people ask about position outages on IGCDroid cell phone recordings. I thought I would share what is happening as this is likely relevant to other pilots and other Android cell phone GPS apps.
Note: As is often true with Android, not all phone behave the same way. In my experience modern phones are worse.
What users see is after 1 hour of recording, GPS recording stops and you only get an occasional blip of positions. This is different to the Glideport not receiving data updates due to cell coverage, this is missing GPS data on the phone itself.
The cause of this outage is Android stops sending GPS positions to IGCDroid. IGCDroid is listening, it just isn't being given any data. My theory is the phone has turned off GPS to save battery power. Modern Android phones are VERY aggressive about saving power as battery life is a big marketing data point. Annoyingly, this happens even if your phone battery is fully charged.
Yes, IGCDroid asks Android to keep the phone and GPS alive. No, power save options make little difference. The only reliable solution I have found is to use external power for your phone.
If you have 5v USB ship power available, that's perfect. Problem solved.
I like to fly with my phone in a parachute strap pouch with a small usb power pack so I have my phone if I do need to bail out. Here is where the story takes an unexpected twist.
usb power packs, by themselves, don't help!!! Modern usb power packs turn off as soon as your phone is charged, at this point you are back to square one with your phone not having external power. Sigh!!!!
Luckily the internet has solutions for this problem. Google "USB power bank keep alive" and you will find a number of solutions. I have ordered this one https://www.tindie.com/products/over...nk-keep-alive/. Its in the post so I can't confirm if it works yet. Fingers crossed.
I have just released a new version of IGCDroid that help diagnose this issue. Flights are tagged with a warning flag if IGCDroid notices GPS outages like this.
If you want to test your phone with IGCDroid here is a simple way to do it... Get the new version ("1.23 (68)" or newer). Go to IGCDroid's Settings menu and set "Record start/stop mode" to "Manual". Now you can use the "Slide to log" control to start/stop a flight. Your phone can be sitting on a table, without moving for the entire test flight. Start a flight and leave the phone UNTOUCHED for a couple of hours or more before stopping the flight. Repeat the test with different power sources. Battery charged, battery low, wall power plug, usb power pack. IGCDroid will tag any flight that have problems.
I hope this helps.
Thanks for your efforts Alan. I haven't had those problems since I
turned off "power saver" mode in my phone, but my phone is probably
older than most (Samsung J7). It will easily run IGCdroid 8+ hours on
the phone's internal battery. The main limitation is that cell signal
is available only intermittently, sometimes no live tracking for 30-60
minutes. But no missing GPS data within the app.
"Power banks" that stay on are hard to find. Some years back I managed
to find one such model, with a slide switch (and built-in flashlight).
It seems identical to this one:
but back then it was labeled a different brand and was 3x cheaper. (I
don't use it for IGCdroid, rather for a stand-alone e-reader or phone
Another option is a simple 4xAA pack with a USB connector and a slide
switch, with 4 NiMH cells it puts out right about 5 volts. Can build
such yourself, but I managed to buy such ready-made some years back.
But best, as Alan said, is to add a 12V to 5V converter to your glider
and run it off the main glider battery (or an auxillary 12V battery).
Pick the least "smart" type of converter. But some may make too much
If you do use external power, be sure to turn the phone's display off
manually, otherwise (with some settings) it will stay on as long as
external power is connected.
But it must be possible to convince a "modern" phone, via user-settable
system settings (outside of the IGCdroid app), to disable the
power-saving modes and keep the GPS data going?