Thoughts on the NHS Covid App

I recently got notified via the NHS app that we had been in contact within somone who had coronavirus. A bit of an initial shock for my wife and I as we have been quite good, since lockdown ended apart from once a week shopping we have only been out 4 times.

The next suprising thing was that we were told to isolate for just 7 days not 14 as advertised. After searching for info via Googgle, we came across an article explaining why only 7. It appears we came into contact with this person probably 7 days earlier at an undisclosed venue and time.

This led us to believe we were probably in the local super store doing our weekly shop.

The Test and Trace app apparently relies on you being within 2 metres of someone for around 15 minutes, it then tags each others phone numbers so it can be used when you log a positive result it can notify all the phones you have been near within that rule.

So it raises a few issues.

  • Bluetooth can be used as a distance gauge, but is more than a bit flakey. Ideally you need three phones to be fairly accurate. Bluetooth works upto a maximum distance of between 10-30 metres, resolution with two phones is therefore not accurate to 2 metres. Also the surrounds may block or enhance the signals.
  • The app does not log GPS data, if it did, it might be able to give you a reasonable idea of where you were on the day. I suspect this was a GDPR concern but in my mind to know where you were on a particular day would be useful.
  • Thirdly, there is no indication of time when you could have been in close proximity to the person. Again this would be useful in identifing where you were at that time.

Some problems I see here as an experienced software developer and database administrator, and even as an individual with a logical mind are :-

  • If you live in a flat and someone is above or below your position and you or they have coronavirus and your app is activated it could be possible to trip the algorithim to log your telephone numbers.
  • I live near a railway crossing that is so renown for being down for 20 mins+, it is so bad it has it’s own Twitter account! I could be in the car behind, infront or to the side with the windows closed and the telehone number could still be exchanged.
  • At the shop I could be checking out one or two checkouts from the infected person, protected by the plastic shields installed to protect the staff as well, I am equally protected but still the telehone number could still be exchanged.
  • The store has it’s own cafe, and the tables are now effectively little bubbles with plastic shields around each table blocking (hopefully) the chance of infection.

I am certainly not against the app, and Test and Trace is a necessity, but it leaves some serious concerns. If any of the three examples above could possibly trigger an alert, why or should I self-isolate? What recourse do you have to override the decision or reversed and how can the integrity of such a override be maintained.

I am fortunate that I work from home, but my wife works with the elderly and has had to stay at home as she was tagged as well.

I do think the data collected needs to include date, time and location plus the telephone number. It would at least offer some comfort to the victim who has got the alert to understand how and when they were exposed.

Also the messaging needs to reflect this, rather than just saying 7 or 14 days. That is a clear message, but we need more information.

There is of course the political and legal issues including why only 18% of those who should self-isolate do. It would need some high profile policing and fines to ensure compliance. I do not think there is the will to prosecute people though. This leaves those obeying the rules, feeling exasperated.

Finally the way to beat the system or reduce the chances of the app tagging you is to turn Test and Trace off when at home and when you believe you are in a safe zone, turning it back on when you leave the zone of safety.

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