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GeneralRe: Not throwing the baby out with the bathwater Pin
Sander Rossel20-Apr-20 20:50
professionalSander Rossel20-Apr-20 20:50 
GeneralRe: Not throwing the baby out with the bathwater Pin
Nelek20-Apr-20 22:24
protectorNelek20-Apr-20 22:24 
GeneralRe: Not throwing the baby out with the bathwater Pin
Johnny YYZ20-Apr-20 22:50
professionalJohnny YYZ20-Apr-20 22:50 
GeneralRe: Not throwing the baby out with the bathwater Pin
Nelek20-Apr-20 23:02
protectorNelek20-Apr-20 23:02 
GeneralRe: Not throwing the baby out with the bathwater Pin
Sander Rossel20-Apr-20 23:00
professionalSander Rossel20-Apr-20 23:00 
GeneralRe: Not throwing the baby out with the bathwater Pin
Nelek20-Apr-20 23:36
protectorNelek20-Apr-20 23:36 
GeneralRe: Not throwing the baby out with the bathwater Pin
Johnny YYZ20-Apr-20 22:49
professionalJohnny YYZ20-Apr-20 22:49 
GeneralRe: Not throwing the baby out with the bathwater Pin
Member 798912220-Apr-20 9:40
MemberMember 798912220-Apr-20 9:40 
1) GPS is not precise enough, especially indoors. You must use something else. All you've got to "measure" with is the signal strength. Phones vary a lot in their transmitted energy, and you don't know which model the other person is using, so you can't tune it from the phone model. Antennas vary greatly as well, an they do not distribute the energy evenly over a sphere. Turn the transmitting, or the receiving, or both phones 90 degrees around each of the three axes - received signal strength may vary considerably. At chip level, many (most?) BT chips allow the transmission power to be adjusted. I don't know if this is available through Android, but if it is, it adds yet another factor in signal strength: Even if you knew the exact model held by the other person, you wouldn't know the raw transmission power.

2) Draw two lines, 6ft apart, and have two people walk towards each other immediately outside the lines. Put their mobile phone in the pocket towards the lines. Let us optimistically assume that both phones report a distance of 6 ft. Then repeat the same test, but now with the phones in the pocket facing away from the lines. Persons meet at exactly the same distance between them. Not only are the phones about 4 ft further apart (2 ft on each side), but also, the signals must go through 4 ft of human flesh, 2 ft on each side. Which distance will the apps report this time?

Bottom line: Distance estimates based on BT signal strength is a joke.

3) You may have been infected up to two weeks ago, in the worst case. For those two weeks, you have been walking around spreading the virus. Even in the best case, within reasonable limits, will it take a couple of days from that other person infected you until he notices any symptoms, either get really sick, or he lines up for a test, which takes some time to analyze, and to get the message back to that other guy, so that he can warn others that he might have affected them. If you were infected, you would be spreading the virus for at least a couple of days.

4) The other guy, who infected you. must himself take the initiative to report to a central cite that he has become sick. Chances are that if if the illness comes very rapidly, chances are small that the first thing he will think of is fiddle around with his smartphone to report to a central site; he might forget it entirely. Furthermore, you must regularly interrogate the central site about all the people you have met, whether any of them have turned sick. So there is another delay, and reliance on explicit actions.

5) You and the other guy must report to the same central site using the same protocols.

6) Very few of my enocounters with other people last for 15 minutes. The great majority are shorter than two minutes: In the streets, at the gas station, in the grocery store. For my family, I don't need an app to tell me that we are close.

7) Everything relies on you always carrying the phone in your pocket, that BT is turned on, that the phone has not run out of battery power. It relies on the other fellow not having left his mobile at home or in the car, that he as BT turned on and has not run out of battery. I am among those who very often to not bring my mobile with me - sometimes deliberately, sometimes just because I forget it.

You describe a solution where you do not poll the central site, but the central site "broadcasts" (it isn't, technically speaking) sends out a push warning to each and every one. In the USA, with at least 200 mill smartphones (probably a lot more) and almost 0.8 million cases, if this system had been active all the time, everybody using it, something in the order of 160 trillion messages would have to be sent out. You must have some way of filtering this, but the central cite knows nothing about who the now sick guy met, they know nothing about location. So how shall they filter it?

The only significant effect of such an app is to keep focus on social distancing. Don't forget it, or you might be caught redhanded by the app. I manage to stay at a reasonably safe distance even without an app!
GeneralRe: Not throwing the baby out with the bathwater Pin
Chris Maunder20-Apr-20 10:06
cofounderChris Maunder20-Apr-20 10:06 
GeneralRe: Not throwing the baby out with the bathwater Pin
Member 798912221-Apr-20 12:23
MemberMember 798912221-Apr-20 12:23 
GeneralRe: Not throwing the baby out with the bathwater Pin
Nelek20-Apr-20 9:44
protectorNelek20-Apr-20 9:44 
GeneralRe: Not throwing the baby out with the bathwater Pin
Chris Maunder20-Apr-20 10:09
cofounderChris Maunder20-Apr-20 10:09 
GeneralRe: Not throwing the baby out with the bathwater Pin
Nelek20-Apr-20 10:44
protectorNelek20-Apr-20 10:44 
GeneralRe: Not throwing the baby out with the bathwater Pin
Chris Maunder20-Apr-20 14:58
cofounderChris Maunder20-Apr-20 14:58 
GeneralRe: Not throwing the baby out with the bathwater Pin
Nelek20-Apr-20 22:20
protectorNelek20-Apr-20 22:20 
GeneralRe: Not throwing the baby out with the bathwater Pin
Gary R. Wheeler20-Apr-20 15:24
MemberGary R. Wheeler20-Apr-20 15:24 
JokeRe: Not throwing the baby out with the bathwater Pin
DJ van Wyk20-Apr-20 20:21
professionalDJ van Wyk20-Apr-20 20:21 
GeneralRe: Not throwing the baby out with the bathwater Pin
Gary R. Wheeler21-Apr-20 1:53
MemberGary R. Wheeler21-Apr-20 1:53 
GeneralRe: Not throwing the baby out with the bathwater Pin
Dougy8320-Apr-20 20:40
MemberDougy8320-Apr-20 20:40 
GeneralRe: Not throwing the baby out with the bathwater Pin
Stuart Dootson20-Apr-20 21:17
professionalStuart Dootson20-Apr-20 21:17 
GeneralRe: Not throwing the baby out with the bathwater Pin
KateAshman20-Apr-20 22:20
MemberKateAshman20-Apr-20 22:20 
GeneralRe: Not throwing the baby out with the bathwater Pin
mdblack9821-Apr-20 3:14
Membermdblack9821-Apr-20 3:14 
GeneralRe: Not throwing the baby out with the bathwater Pin
Member 778295321-Apr-20 7:11
MemberMember 778295321-Apr-20 7:11 
GeneralRe: Not throwing the baby out with the bathwater Pin
Peter Kassenaar21-Apr-20 21:11
MemberPeter Kassenaar21-Apr-20 21:11 
GeneralRe: To the guy asking if we'd using COVID-19 tracking apps... Pin
Dar Brett20-Apr-20 19:49
MemberDar Brett20-Apr-20 19:49 

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