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Testing so far is limited, but it looks like we have made significant progress on both aspects
Some concerns remain - I plan more testing to try to better understand the specific issues that may remain.
Summary of changes
Android Apkhttps://tinyurl.com/covidsafepath
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One important note:- It might be possible that after 2 min if the user stop app and start after 2 hours then those 2 hours will not be recorded and can not be treated and that user was there at the same location.
Test Results
These results are after 16 hours. During this time, the phone was left powered on in a single location (indoors).
Initially the app was open, but was closed after an hour or so - I don’t have a record of the precise time.
Reliability
The chart on the left shows the time gaps between GPS logs (on a log scale) - which is much more reliable than the data from the previous build (20 May) on the right (albeit over a slightly shorter time period).
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App is in foreground
App is in background, but phone is in use for other activities
App is brought to foreground & data exported.
Accuracy
Distance variation (left) is improved massively from previous test results (right)
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The final data point, which shows a sudden move of 39m. The phone had remained stationary. This correlates to the app being starting up, and also seems to correlate to a loss of about an hour’s data (see reliability above). I will aim for some more testing around these operations.
We have only tested with a stationary phone. Next step would be to test the app with 2 or 3 phones moving around together, and compare accuracy.
Battery usage
My phone reports 2% of battery usage by the app over the last 16 hours.
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So there’s certainly no evidence so far that battery consumption has got any worse, and it may even have got better. More testing needed, but no immediate concerns here.
Update - 26 May
Further testing from 6pm on Saturday 23 May to evening on Tuesday 26 May suggests improvements may be less significant than initially thought.
My phone has been logging in the background over the weekend. After a phone reboot on Saturday afternoon, logging had stopped (don’t yet have the fix for that problem running). I restarted the app at 6pm.
Since then, I have been moving about so can’t give a reliable position on accuracy.
But reliability has been poor - no better than before the fixes.
Here’s a graph of the data (log scale so that we can see both small & large delays on a single scale)
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This looks much like it did previously.
Over the period, we had
Just 61% of the expected data points (535 of 879)
22% > 6 mins apart
17% > 9 mins
3% > 14 mins
2% > 29 mins.
Notable long delays:
Saturday night:
00:50:43, 01:56:41, 03:56:21, 01:42:50
Sunday night:
02:54:05, 05:48:28
Monday night:
No big gaps (steady 5 min logs throughout).
Daytime gaps > 20 mins:
Sun: 26:45, 53:41, 34:54, 20:56
Mon: 24:59,
Tue: 29:59, 42:28, 51:40.
So we are still seeing:
Very long gaps at night
Occasional long (30-60 min) delays in the day.
Plenty of occasions where logs are 6-10 mins apart.
Overall, I see no significant improvement from the previous software. Which is odd, because the 1st 24 hours after install of the new software seemed much better.
Either that was just a lucky period of time - or there is something unusual abotu a fresh install of the app.