# Proximity enter/exit latency

#1

How fast can the ProximityObserver detect the enter/exit? I did some testing, it varies to seconds, if there any config to make the latency below 1s?

#2

It’s hard to speak about latency in the context of the Proximity SDK, because the enter/exit trigger range is not exact. What exactly are you trying to do?

#3

It is expected to announce the enter event with low latency, desired to be < 1s. So if it is close to the beacon, it should quick announce the event. Exit is less important,

Does the ProximityObserver poll the distance? is there any way to expose the polling frequency.

#4

How would you propose to measure that?

Say, for example, you set the desired enter trigger distance to 1 m. This means that as soon as our internal algorithms determine that the distance to the beacon is 1 m, they trigger an enter. Does that mean 0 latency? Probably not, as we’re doing some computations to smooth the signal, so even in a perfect world with 100% accuracy, there would be slight delay.

But to complicate things even more, it’s not a perfect world, and the Bluetooth radio waves are tricky, so e.g. you might be 2 m away from the beacon, but we get a spike in the signal strength enough to trigger the enter. Does that mean “negative” latency, because you got the event sooner than expected? Probably not, it’s an accuracy problem, not a latency problem.

Similar, what if you’re 1 m away from the beacon, but somebody is obstructing the signal, and our internal algorithm thinks you’re really 2 m away. That person moves away after 1 minute, and now we trigger the enter. Does that mean 1-minute latency? Again, probably not, b/c it’s more of an accuracy problem.

That’s why we don’t think it makes sense to try and define latency for Proximity enter/exits.

TL;DR If you’re trying to e.g., build a race-track system and detect when a runner/cycler/etc. passes a beacon with < 1 s precision, then beacons are probably not a good fit for that. If you need to know when somebody is within a certain area with some reasonable leeway (say, something between 1-30 seconds), then Proximity should be fine.