Lost my iPhone last Wednesday. I realized it was gone the next day and used the “find my iPhone” app to try to locate it. The app gave a particular address which I had not been anywhere near. The people there were nice and let me look in their back yard, and even let me use their phone to try to call my lost phone There was no answer, which is to be expected since I disabled the phone via the app. I don’t believe they know anything about my lost phone. On Friday morning the app said my phone was at the same location I had lost it it at, then an hour later it had moved to the duplex next door to where it had been(?) on Thursday. That address was clearly unoccupied. I could see through the window that there was no furniture.
My question is: What is the margin of error for locations given by the “find my iPhone” app?
The margin of error depends on how well it can detect the GPS constellation, cell towers, and some wifi and Bluetooth transmitters. I’ve seen errors as low as a single room in a house to as bad as over a mile.
Once you’re close to where the app thinks your phone, use the app to have the phone play a sound. This is not the same as calling it. Calling it might not work, or the ringer could be off, etc. Using the app to play the sound overrides all that and makes a loud sound. That’s your best chance to finding it.
It’s variable, IME. Last year my daughter lost her cellphone walking from school to her car. The app initially placed it about a 1/4 mile away from the school, in the operate direction. But later in the day when I looked for it, the app located it to within a few yards of the snowbank it was buried in right near where her car had been parked. So the initial location was completely wrong. The sound made it pretty easy to locate, too.
My daughter used it to find her phone in a dept store, in someone’s pocket. They had slipped it out of her purse. And then (dumb criminals) hung around the store, the loud tone it sounded convinced the thief to hand it over. He left really quickly after that.
Surely it’d be the same level of accuracy as the positioning on the map when you’re using a navigation app? “In 100 feet, turn left onto Main Street. Turn left onto Main Street”. Those are generally pretty close; why wouldn’t Find My Phone be similar?
I’ve thought I lost my phone twice, checked the app and found it to still be in my building. Both times I set it to make a sound and found it by that. Once was on the floor of the back seat of my car and I have no idea how it ended up there. The other time it had fallen behind a chair in my bedroom.
When you click on your device in “Find my iPhone” and zoom into the map, it should give you an idea of the accuracy. My iPhone shows a green circle showing an accuracy radius of about 30-40 feet. My iPad, though, is showing a bit lower accuracy–maybe about 60-70 feet?
Anyhow, looking on the map overlaid with the satellite imagery, the app shows my phone on the sidewalk in front of the house two doors down from me. It’s a little closer on my iPad to my actual location, showing my iPad somewhere in my front lawn.
ETA: Actually, looking now at the green circle for my phone where accuracy is established, the actual position of my phone is a good bit outside the accuracy circle, almost another full radius. The iPad’s location is well within the accuracy circle.
GPS works best with line of sight to the sky. In a deep canyon with solid rock between you and any satellite it won’t work at all. Inside a building there is much more to block or interfere with the signal than there is in a car. So you will generally get a much better signal when driving around that you will inside a building.
It’s possible that you may get a better fix when you’re in a very substantial building that blocks the signal completely, because the phone will just go by the last good signal when you entered (provided it was switched on, of course). If there is a poor quality fix inside the building, it may update but be inaccurate.
I don’t believe that the green circle shown by Find my iPhone is really indicative of the location accuracy.
If it can’t get a GPS location, it’s going to rely on cell tower triangulation and available wifi names, which is much less reliable.
If it can’t get those but somehow has an IP address, it’s going to give you some location approximately in the center of where that IP block is given out, which might be very inaccurate.
There have some unfortunate news stories about people who live at the geographic center of some large-ish area who get daily (or worse) visitors accusing them of having stolen their iPhones.
I assume the battery is dead by now and Find my iPhone no longer works? You can use Find My iPhone to make the phone play a loud sound even if the phone is on silent. That would work even when calling it doesn’t. My daughter left her’s on the back of the school bus and that sound was loud enough that the bus driver heard it from the front and found the phone.
Why not? I mean, if an anonymous tip gets called in that someone has “a bunch of drugs or guns” at their house, *that’s *enough for a search warrant, right?
Apple doesn’t have any reason to lie and their technology in itself doesn’t deliberately lie, obviously it can glitch.
Is it because the phone finding isn’t accurate enough? If it worked better would it be enough for a warrant?
The real reason I ask is on a totally different topic. Autonomous cars could very accurately video and monitor other vehicles, and be made to automatically detect violations of the law and report them.
An autonomous car manufacturer has no reason to lie, to “get” a specific individual human driver. So I kind of feel a crystal clear video, maybe taken from several autonomous cars from different angles, of a human driven car committing a traffic violation should be enough for a ticket. Even if a cop didn’t personally see it, they should be able to review the video and that should count.
This would create a zero-tolerance set of roadways, and would force most humans to stop driving, which would save thousands of lives.
Just for fun, I checked it again. My phone and iPad are with me in the house, right next to each other. The iPad is showing up as being in one of my neighbor’s garages. Actually, it’s right between the two garages of my two neighbors to the north of me. My iPhone is showing up in my front lawn, probably about a good 30-40 feet due west of its real location. Oh… wait. My iPad just moved. Now it’s definitely in the garage of the neighbor directly north of me.
So, yeah, I certainly hope these things aren’t good enough for warrants. I mean, yes, it’s in the general ballpark, but doesn’t seem to be accurate enough to pinpoint an exact house with any degree of certainty.
Let me try an experiment and walk around with the iPad and see if it registers a little more closely to my real location.
walks away
returns
OK, now my iPad is apparently in the street of the neighbor south of me (where his car is parked). Apparently, my phone is now located there, too, so at least both devices are showing up as being physically co-located, although outside my house. Oh, wait. My iPad now somehow crossed the street. So, the difference between the initial position it reported my iPad at (when it was in my neighbor’s garage) to where it is showing now is about 125 feet (based on my knowledge of the size of city lots here in Chicago.) It looks like it was off by about 70 feet with its first location estimate and 55 feet with its current location estimate from the true location of the device. I do not live in a location with a lot of high buildings or anything. All the residential houses for miles around are one or two storey homes, with maybe a three flat thrown in there here and there. I am, however, inside my two storey house, so I’m sure that is somewhat affecting accuracy.
Navigation apps aren’t always that accurate either. That said, navigation apps have the benefit of knowing you are on a road so if the position has you driving through houses it can safely assume you are on the nearest road and adjust your position accordingly. At least that is how my car nav system works.
A navigation app makes used of more information: your velocity and a map. A GPS solution typically gives velocity information, but that’s not particularly helpful to an app like Find My iPhone. But for a navigation app, it can match the direction of the velocity with the direction of nearby roads and then find the best solution where your position is on a road going the same way you’re going.
You can mess this up by using the app while not travelling along a mapped road. I’ve done this by travelling on a new road. The first time we went across the Hoover Dam on the new bridge, the nav got seriously confused and then gave up and assumed we were flying through the air; which we kind of were when you compare the old road to the new overpass. Or, use a nav app while on the train–it kept placing us on nearby roads. It’s interesting to watch it flip from a nearby road going the wrong the way to a farther road going the same direction. (Optimization when your underlying hypothesis is wrong is fraught.) But the app reported our speed quite well the whole time.
It’s a great feature, Find My iPhone. My wife is Type 1 diabetic and I have a CGM viewer on my devices — Continuous Glucose Monitor. Between Find My iPhone, Find My Friends, and that CGM (Dexcom G5 and Dexcom Share on her devices, Dexcom Follow on mine), I can check her blood glucose levels from anywhere in the world, like when I’ve traveled to China or Europe and she stayed home in California.
Once last year I was out of town and my Dexcom Follow app was alarming — her blood sugar dropped too low. I was a 2-hr drive away. I called and called. No answer. I sent a Find My iPhone sound to her phone. No response. But from that and Find My Friends I could see where she was.
I called 911 to send paramedics, and they got to her quickly. I told them to check blood glucose and to treat that. It was a happy ending, and meanwhile I was now driving home quickly. But the 911 dispatcher and the paramedics wanted to know how I knew — “She is where? And you are where? And how do you know this??”
There’s obviously some level of correction going on with the navigation apps, as if I take an unexpected exit (that is, say I’m on the interstate, and instead of continuing onward as the app is telling me to, I exit for gas), it takes several seconds or more for the app to figure out I’m not on the main road anymore. It’ll have me on the main road until I’m maybe a good 20-30 yards out, and if I’m simply on a parallel road (like a frontage road), it may not even notice until I turn perpendicular to the highway.
That said, the older systems didn’t seem to have or be as good at this correction. I had a Garmin 10-15 years back that just went nuts when I was driving downtown and put me in all sorts of impossible places (like I mentioned before, in the middle of the Chicago River. I thought that it was my phone that did that years ago, but now I think it actually was the Garmin GPS. The phone will screw up by locating me on the wrong street when I’m exiting a parking garage, often showing me going in the opposite or orthogonal direction to where I’m actually going until a few seconds later it gets enough data to figure it out.)
