I have an issue that i am having trouble to solve. We are about to develop an iphone locative application that would take you around the city with audio that would be played based on the location. I was wondering, do you know how accurate the iphone GPS will be? In terms of actual distance. I am reading 250 m on line but it looks a lot. Plus the gps in the iphone finds my location more precisley than 250 m. I know it is a generic question, but mabe you guys can give me a feedback about it, i am quite desperate and exausted. what we would live to do is, every 70-80 m, put a pin on a map with an audio file, when the user crossed the pin it would trigger an event that is the audio file. I just would love to know how accurate the gps could be so that i can start designing the experience.
Thanks a lot
I've seen iPhone's GPS as accurate as 3m (at least that's what it said on my device when testing).
There is also a new API since iOS 4.0 that you might be interested in that will enable you to set a region for the device to monitor and it will automatically generate a callback when the user crosses the virtual fenceline depending on how accurate you need that to be. This is particularly useful when the app is sent to the background since you can simply monitor the user's location using CLLocation when the app is in the foreground:
- (void)startMonitoringForRegion:(CLRegion *)region desiredAccuracy:(CLLocationAccuracy)accuracy
You can get up to 5 meters accuracy. Within the core location framework there is a property - horizontalAccurracy - that you can read at runtime to get the accuracy for a given moment
The accuracy is anywhere from 5-25m.
Related
I want to make an app that knows the last time the iPhone moved more than 1 meter. I can't use the motion accelerometer APIs because it also needs to detect from the background.
The answers to this question imply the CLLocationManager continually improves its guess:
iPhone GPS Accuracy - Reading Changes eventhough Device is stationary
I don't care where the phone is, just whether it has moved more than 1m. Is it possible to infer this from the location events?
No this is not possible since the GPS signal is not accurate to that level.
Also the indoor GPS reception is total depended on the type if building you are in.
On the first floor of a high building you will have 0 to no reception. While in a wooden shet you could have perfect reception.
Unfortunately no.
However, you have some options for indoor localization, see my answer here.
I was wondering if it was possible to get the location of the iPhone with an app that isnt running, or at least running in the background. What I want to do is have the iPhone send a push notification when it arrives at a certain coordinate. Is this possible? If so, could someone put me in the right direction?
Thanks,
Ben
Yes, it is possible. Your application can ask to be notified of significant location changes or to simply continue using the GPS while executing in the background. The former—the approach recommended by Apple—uses less power at the cost of accuracy (this blog post indicates that the updates are accurate to roughly 500m), while the latter is as accurate as the device can manage. This is all detailed in the iOS Application Programming Guide and and the Location Awareness Programming Guide.
If you simply want your application to be notified when the device moves into a particular region, you may want to look into CLLocationManager's startMonitoringForRegion:desiredAccuracy:. If the device moves into a particular geographical region, your app is launched (even if it's not running!).
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.
I'm looking into the new background location service options in the iPhone 4 SDK. It allows an app to run in the background and receive location updates from the device.
There are two methods offered. One is a battery intensive mode that continuously gets location updates. The second recommended method sends the app location updates when there has been a "significant location change".
Does anyone know what a significant location change might be? Is a 30 foot walk considered significant, or is a 10 block walk considered significant? I imagine it also depends on the accuracy of the location mechanism being used at the time.
I've recently done some field testing of the new background location service to get an idea of what constitutes a significant location update, what kind of accuracy to expect for the location hits and our general experiences using it.
The results are detailed in a fairly lengthy blog post:
iPhone Background GPS: Accurate to 500 meters, not enough for foot traffic
As Steve Jobs mentioned in the OS 4 introduction, the low power mode uses cell tower triangulation and does not activate GPS unit. Since the iPhone phone module needs to keep a connection to the cell network anyway, there should be no impact on battery life.
Since the precision of a location fix with cell tower triangulation is anywhere between a few dozen meters (in dense city locations) and a few miles, I think 30 ft is not a significant location change. I don't know the specifics, though (and as mentioned by the commenters, the Apple dev forums are the right place to talk about those).
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.