[jukea]

I once found my phone buried in the sand on a beach with no coverage. I had a year worth of pictures on it, so I stewed in anguish for almost a day until we thought about installing a Bluetooth signal monitor on a friend’s phone . Given the sluggish update frequency, we resorted to triangulating the phone’s position. As we were pulling it from its sandy grave, I swear it felt like we were cheating fate itself.

[lxgr]

I recovered a lost device (satellite messenger in my case) via Bluetooth as well! It had just fallen into some ferns a meter or so off the trail, but without Bluetooth I'm sure I'd have never found it again.

[WanderPanda]

Not to nitpick but I think you mean trilaterate ;)

[lxgr]

If we're being nitpicky it was probably neither – multilateration requires taking multiple measurements, drawing circles/lines of equal signal strength (or timing advance) and then intersecting these.

If you just want to home in on a transmitter, there's a much simpler algorithm: Try walking into various directions and keep heading into the one that makes the signal strength nunber go up :) Not sure if there's a name for that.

[dharmab]

Direction finding! https://en.wikipedia.org/wiki/Direction_finding

[lxgr]

I was looking at that too, but doesn't that usually imply using a directional antenna, rather than just measuring the received signal strength at different locations?

[aarghh]

Nope - as everyone who has looked for a buried avalanche beacon knows. As a matter of fact, depending on the number of burials and the searchers, your optimal search technique may be different.

[jffry]

> Not sure if there's a name for that.

Hill climbing! https://en.wikipedia.org/wiki/Hill_climbing

Basically: Go in any direction that makes the number go up. Repeat.

[petemir]

Gradient ascent?

[TeMPOraL]

Or gradient descent if you mentally negate the number in question. It's the same thing.

[WanderPanda]

I think hill-climbing rejects updates that would worsen the objective while gradient descent usually doesn‘t

[fsckboy]

you need a second rule: "Don't go in any direction that makes the number go down." That way, when you're on top of it, you know to stop.

[freshboy69]

No you don't. Go in the upward direction implies don't go in the downward direction

[fsckboy]

I don't agree that that wording is as precise as you think it is. if you move in the direction where the signal goes up, when it stops going up, you are still moving in the same direction. Move "so long as the signal goes up" would tell you to stop, but it wouldn't tell you the direction, is the type of clarity I'm looking for.

[smegsicle]

"warmer colder"

[jukea]

Nice one, Yep this is it. We drew 3 rough circles and found the intersection

[tkk13909]

And this, kids, is why we back up everything