I’m primarily talking about stuff like step counters, but also health apps measuring your heart rate, how many stairs you take, the length of your steps, and so on. I’m honest when you tell me to explain it to me like I’m five years old, this one boggles my mind.
GPS is good enough now to know what room you’re in, I’ve tested it at my house. It can tell the difference between the 30 feet or so between my bedroom and front door. Someone else in this thread says it’s accurate to about 5 meters.
A radius of 5 meters- 15 feet or so. Which of you consider the scale of what’s going on (satellites in orbit, pinging your location to a relative pin prick, accounting for relativity,) it’s fucking impressive.
But you might be anywhere along a thirty foot line.
And that’s at its most optimal conditions. Inside a building (particularly commercial or industrial, and particularly larger buildings,) that becomes much, much more problematic.
Which is why they use combinations of things like WiFi location (“improved location services”) to increase accuracy as well as dead reckoning using your accelerometer.
But ultimately, that’s all just a guess, and they’ll frequently cheat. For example, if you pull under an overpass and stop, pretty quickly they’ll start wigging out bouncing you between the road above you or the one you’re actually on. Or when you decide to ignore navigation instructions on the highway- which is why until it updates the map it’ll still show you on the offered route. (Which might be 200 ft down the road, and 50ft away.)
All of that to say that they’re using a lot of tricks to convince you that it’s a lot more precise than it really is.
There’s another trick - checking against street maps. When you walk/drive/ride around a corner the phone can use it’s inaccurate GPS reading and update it according to where the corner is. Of course it doesn’t use ONE corner. to fully update your position, it just nudges the position a bit closer.
In case you are navigating a lot of street corners, after a time an inaccurate GPS position will be corrected.
There’s even more input to the algorithm (location of known WIFI Hotspots for example etc) and they are all combined with a “Kalman filter”.
https://en.m.wikipedia.org/wiki/Kalman_filter
As well as the us military intentionally keeps GPS readings inaccurate, as conspiracy theorist as that sounds lol
This hasn’t been true for 24 years.