Last night I lost my iPhone (pro 13 max) on the train.
The phone is off, as when my friends try to call it it goes straight to voice message. However, using an old iPhone, I can use "Find My" to see that it is somewhere with around a 15m radius close to a train station quite far away, and actually seems to continuously update its location roughly every hour or so, despite being off? This is a fairly rural station, so no shops or apartments/houses it could be left at. If "Find My" is correct, Its just somewhere around the station.
I spent ages looking around in the area, continuously checking "Find My" again on my old phone (which had no internet connection, data sim in lost phone). Suddenly, I found that when I went to a very specific area, the "last seen" on my old phone updated to "Now" and the radius reduced to around 3m around where I was standing...
Does that even make any sense? Are my devices communicating, despite one of them being dead and the other not being connected to the internet?
I couldnt find it, but there was a lot of shrubbery and dead leaves around, so I am returning with a metal detector tomorrow.
If your iPhone battery is dead, you can view the last location before the battery died, but you cannot track it. If the iPhone is turned off but still has battery, you can track it as long as you have Find My enabled.
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I want to create an (game based) iPhone application which sends your GPS location on a specific time (like 3-5 times a day) to a server. I found an apple page explaining some functionality to run in the background like location, music and VOIP.
I need the GPS to be accurate on the meter.
Can someone help me with a small example?
It really depends on your usage of the location. If you monitor actively, kiss the battery of your user goodbye. Very detailed accuracy, even bigger hit to battery. The backgrounding of location is all or nothing as far as accuracy goes.
Less hit, less accuracy is -startMonitoringForSignificantLocationChange. May not be accurate enough for you.
Better depending on usage, region monitoring. Triggers event on entry or exit of defined region.
You don't have the benefit of accuracy and timed location based events. You can do it, but is going to require a lot more effort on your end.
While this is untested, I am planning an app with a similar need. My solution is that on a significant location change, the app will determine what interval exists between the update timestamp, and when I care to know the users location (5pm for instance). If that's below some threshold, it will go into startUpdatingLocation mode (full power, battery draining, which is why that threshold is important) and then, on each location update, check if that target time has passed. if SO, send the update to your server, and go back to monitoring for significant changes. The catch is that if it still requires some movement to trigger the significant change update...so it isn't a perfectly reliable solution, but it may work depending on how you're using the data
You can't "schedule background work". iOS doesn't allow it.
The solution is to set yourself up for notification on significant change (which is some hit to the battery, but it's not horrible), and then only DO anything with that at occasional intervals.
quick question. How accurate is the GPS on the iPhone 4? I ask because I'm working on an enterprise project for a company, and part 2 of it will deal with iDevice development where I have to determine the position of the user. I'd like to know if the GPS is accurate enough to sense the user moving within rooms because the user will have to "tag" sections of the room as they move about it.
Thanks in advance!
P.S. Pressuming that it won't make much of a difference, but the users will actually end up using the iPads, not iPhones, and more than likely the iPad 2 will be out by the time the entire project is completed. I don't know if the iPad 2 will have a better GPS receiver or not, but at the minimum I should use the iPad/iPhone 4 GPS receiver...
Most buildings will not allow reception of an accurate set of GPS signals (if they can be received at all) indoors. The roof/ceiling/floors above are just too thick. Even a lot of trees overhanging a building will degrade the signal from the GPS satellites.
You might have a chance if all the rooms have very large unobstructed windows with no overhangs, and it's the right time of day for several satellites to be in view out that window.
Outdoors, in the clear, the iPhone 4 GPS seems to be very accurate. Sometimes I can walk around my parked car, and see the blue dot in the Maps app follow me in a circle.
I have done some work with a large location data set. My result set is based on cars driving outside and will therefore be, on average, more accurate than those taken inside (based on line of sight to satellites).
For the 650,704 location updates I used in my tests, I found the average accuracy radius was 246m (91m if your remove >1km outliers). 85.1% of updates had an accuracy of less than 100m. So given that your update will not be as accurate as these, I don't imagine you will have much success tracking indoor location changes.
For a further description of my results.
It is very difficult, and most of the time impossible to obtain a GPS signal inside a building. The type of waves used by the GPS (radio waves) are not powerful enough to go through the structure itself.
A simpler and probably cheaper solution would be to give people maybe tags or cards and install some sort of trnasreceiver in each room.
It seems the original question was "how accurate is the GPS on an iPhone 4", which hasn't exactly been answered yet.
I've done lots of testing with the accuracy of the GPS chips in iPhone 4, iPhone 4s, and iPhone 5, and the most accurate reading allowed seems to be ~5 meters, or ~16 feet when you're outside with clear line of sight to the sky. I'm guessing this is a software limitation imposed by Apple to conserve battery.
How much does active GPS drain the battery? Without the overhead of the gps navigator software. s
ay I want to sample the gps every 2 minutes and save it to a file. how much battery power will that cost me?
Will I get 10% shorter life? 20%? ..?
I think this can't be answered that easy without measuring it. But you could measure it. Just try how long it takes to empty the whole battery. Once with GPS and once without.
It will be noticeable by the user. You definitely don't want to do this kind of thing unless it is a feature the user is explicitly aware of and able to clearly turn on and off depending on whether at any particular time they think that feature is worth the impact on their battery.
On my HTC Desire, RunKeeper with GPS always active, battery was near to down after about 5 hours of usage (in forrest).
But the screen was down while it was running, 2 hours of reading pdf drains about 40-50% of battery, so GPS working in background drains about same or less energy than screen active.
When you turn the GPS on, you must wait, depending on where you are, before you get the read, so if you want to save position every 2 minutes, I think GPS will be on about 25%-50% of time. 10 hours of work in background would be max in that case...
Maybe the question about increasing battery life on Windows Mobile using GPS will give some hints, since the device used in test was manufactured by HTC, which is one of the most popular manufacturer of Android Devices nowadays...
This afternoon I walked my iPhone 4 into the Apple Store to see if they could help with a problem I've been having. Battery life hasn't been AT ALL what it should be--the battery drops 50% sitting on my desk overnight. Crazy. So I suspect I've got a bum unit. Happens. No biggie.
My friendly genius pokes around my phone a bit, and points out that the Location Services pointer is lit in the top right corner of the screen. He gets into the location services settings. He notes that the following apps have the "got location data in the last few hours" flag lit: The Weather Channel, Showtimes, and two apps I wrote and am days away from submitting.
He turns off the sliders for each of those apps, and we see the top corner location services pointer turn off. Turning back on location services for EITHER of my apps makes it turn back on, and that's NOT the case for Weather Channel or Showtimes. But it's clear that turning on location services for my two apps fires up the device's location services. My lousy battery life is explained, but that's just the beginning of the mystery.
Here's the thing.... Neither of my apps are EVEN RUNNING at the time. They're not even backgrounded. They're OFF. I think they're both built in a debugging profile on my device at the moment, and they both do use Core Location. They're not suspended, they're just flat not running. And yet, turning on the slider in the location services control panel for either of them fires up location services in general.
So... What the heck is happening here? Neither of those apps are configured for background location. And... they're not IN the background! And since I've had location services turned off for them, there's no doubt my battery usage is way way down.
The solution is at this thread in the Apple developer forum: https://devforums.apple.com/thread/58063?tstart=0
An earlier version of both of these apps had called [locationManager startMonitoringSignificantLocationChanges], and never called stopMonitoring.... Even though the current version of the apps didn't make that call, the OS still had the monitoring request "registered" to the apps (and was, in fact, relaunching them in the background as I drove around town!).
What I didn't know was that the monitoring request persists across launches--and across re-builds! I'd assumed that, like -startUpdatingLocation, the monitoring request would die with the process, but not so. The solution was to delete the apps from my device and reinstall.
In my application the user will hold the iPhone and walk in straight line, iPhone will alert the user every 2 meters to make lux measurements and record them. Is the GPS on the iPhone accurate enough for such task? (given that the place is the runway of the airport and should have clear reception of GPS satellites signals...)
No, you won't get that good a fix. 2m is about the limit of GPS and that usually requires significant time without moving. 10m seems to be what you should be able to get, though I've heard worse and (obviously Ole above) better.
The best reported GPS accuracy I ever got was about 7 m. Why don't you build a simple sample app and test it for yourself? It should only take a few minutes.