i want to know how accurate our gps on iphone 4/4S because my new project is using gps for tracking something. i mean accurate is about meter. I have search other question like mine but i don't have the answer. Is it possible to track radius just say for 1 meter? how long accuracy that the gps iphone 4/4s have (in minimum)? 10 meter? how about 1 meter? can it track for 1 meter radius? oh again, my next project for my company is outdoor application. I know i can test it by myself but it more quick to get the answer from here. thank you.
The simple answer is: No, it's not accurate down to 1m.
In some cases though it is, but don't count on it. In an urban landscape I've sometimes been displaced by about 20m. but it seems like all devices gets the same displacement, so you can detect if they are close or not.
Edit: I should say that I have worked a lot with the location services on the iphone, so I'm absolutely sure of this answer.
I have tested the 4S using the standard GPS test of positioning the unit over a known point (survey point - 1 cm accuracy) for a specific period of time. This 30 minute continuous test was done in Tucson, AZ (good GPS territory) versus New York City (tall buildings and further north) using GPS Photo-Link. So we typically look for 10 meter accuracy which means that 92% to 97% of the points are within 10 meters NSEW of the known point. The iPhone failed the first test so I tossed the results and stopped testing it. I am waiting for WAAS on phones to see phones improve GPS but I think most phone companies are going to throw their money into making the camera better.
Well, may be you can set the accuracy you want like
CLLocationManager *locationManager = [[CLLocationManager alloc] init];
locationManager.delegate = self;
locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
locationManager.distanceFilter = 10;
[locationManager startUpdatingLocation];
For more information please refer apple documentation
Hope this help you. good luck.
Related
I am new to iOS.
I am making one app using GPS location update.
I am fetching current location and update location to server.
I want to get every change in meter and update it to server.
Here is the code i am using:
locationManager = [[CLLocationManager alloc] init] ;
locationManager.delegate = self; // send loc updates to myself
locationManager.distanceFilter = 1.0f; // whenever we move
locationManager.desiredAccuracy = kCLLocationAccuracyBest;
[locationManager startUpdatingLocation];
But the location is not updating after every meter. It updates but not regularly.
Thanks for Help!
It doesn't work like that. AGPS, which is what iPhone uses, has limited accuracy which depends on many factors. It uses GPS, Wi-Fi and Cell Towers triangulation and at any given moment it can use any combination of these. So, when GPS signal is lost and there is no Wi-Fi hotspots around you could be getting location based on Cell Towers location which is very inaccurate (a few hundred meters). It could be worse than that, you could be getting cached location which is nowhere near your current location. And even when you have GPS signal you can't expect to get 1 meter accurate location everywhere you go. GPS accuracy itself depends on many factors.
Use kCLLocationAccuracyBestForNavigation always. There is no real battery usage difference between that and kCLLocationAccuracyBest, they both use the GPS at top speed. The main difference is in the post-processing that Apple does.So you can try the kCLLocationAccuracyBestForNavigation.
I have code that creates a geofence on my iPhone that will trigger some code to be executed when didExitRegion gets called. However, I have found that when I have WiFi switched off that didExitRegion never gets triggered.
Is WiFi required for monitoring region changes on iOS?
My desired accuracy is set to kCLLocationAccuracyHundredMeters.
I am testing on iOS 6.1 and iPhone 4.
Here is my code for setting up location monitoring:
- (id)init {
self = [super init];
if (self) {
CLLocationManager *manager = [[CLLocationManager alloc] init];
manager.delegate = self;
manager.desiredAccuracy = kCLLocationAccuracyHundredMeters;
manager.distanceFilter = RADIUS/10.0;
manager.headingFilter = kCLHeadingFilterNone;
self.locationManager = manager;
self.authorizationStatus = [CLLocationManager authorizationStatus];
}
return self;
}
Thanks
iOS devices use three methods to discover user location. From (usually) most accurate to least accurate they are:
GPS hardware
By identifying nearby wifi networks
Cell Tower Triangulation
If your app doesn't use GPS or is not running (ie. has previously been terminated), the device will attempt to use methods 2 and 3 above to locate the user. So the device's ability to locate the user (when the GPS hardware is not in use or there is a weak GPS signal) depends on the availability of wifi networks and cell towers. The more wifi networks and cell towers, the better the location accuracy. Therefore, when a user enters or exits a monitored region (ie. crosses a "geofence"), it is impossible to predict exactly when the user will receive the notification if at all. (Of course, if the region in question is always the same, the device will more or less locate the user with the same degree of accuracy on each occasion).
Here's the relevant documentation from the Location Awareness Programming Guide:
The specific threshold distances are determined by the hardware and the location technologies that are currently available. For example, if Wi-Fi is disabled, region monitoring is significantly less accurate. However, for testing purposes, you can assume that the minimum distance is approximately 200 meters.
So, wifi is not required for region monitoring to work, but with it enabled, your device will have a better chance in determining whether or not the user has crossed a region's geofence.
If you turn off WiFi, your location accuracy lowers. If you don't have GPS signal(inside some buildings), you will not get any location updates. Have you tried this when you are outside, or if you used the location simulator to test?
Also, WiFI is not required for geofence function if you have GPS(iPhones or iPad with sims).
Weird weird stuff can happen without wifi using core location. To help in your case I would get rid of the distance filter, that can mess with things and it is not very helpful. I would probably only use kCLLocationAccuracyBest for anything where I need the accuracy required to set up a geofence. Using other accuracies and filters for me would sometimes through the gps meter off by 1000 meters and take a minute or two to correct itself. If this is too much battery then set up a system where it turns off and on based on how far away it is from the fence.
I have configured locationManager as follows.
_locationManager = [[CLLocationManager alloc] init];
[_locationManager setDelegate:self];
[_locationManager setDesiredAccuracy:kCLLocationAccuracyNearestTenMeters];
[_locationManager setDistanceFilter:kCLDistanceFilterNone];
When the application runs, I get some updates from the delegate methods.
And when I do not change the location, and the mobile is stationary for about 2 hrs, I receive about 10-12 updates in the first 10 mins, and then stop receiving updates.
What I understand is that desiredAccuracy is how long the device will keep trying more and more accurate methods to get the current location. So in my case, it takes about 10 mins to get the desired accuracy.
I want to confirm if this is true. Also is there a way where I can get regular location updates even if the device is not moving?
Why would you expect the location to be updated if it hasn't changed?
If you want to periodically refresh your results, use an NSTimer you've created yourself.
When the device gets a location with a margin of error < desiredAccuracy, it will stop asking for more accurate results. If the device moves then it will start asking again, until it once again gets the location to the desired accuracy.
If you're specifying 10m for the accuracy then you're almost certainly going to be relying on GPS - cell towers and wifi aren't that accurate (usually).
To determine if the device has moved, it uses distance filter - by setting this to none you are asking it to be accurate to the nearest 10m all the time - this is probably going to be quite draining on the battery ;)
I having some problem on the iPhone/iPad compass development.
The trueHeading taken from the CLHeading alway give me the '-1' value, I'm stuck here. Here is my code:
self.locationManager = [[[CLLocationManager alloc] init] autorelease];
self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;
self.locationManager.delegate = self;
self.locationManager.headingFilter = 0.5; //1 degrees
[self.locationManager startUpdatingHeading];
I also found out something, that is when I on the map app or the compass app which has use the location stuff, the trueHeading value suddenly read correct. I wonder what is the cause, any idea? It happen on both iPhone4 and on the iPad.
It also happen whenever I off the Location Services in settings and re-enable it, it will become unable to read the correct trueHeading value, i wonder because the location services cannot be enable by the app I creating?
anyway, thank in advance
---My Solution---
see below.
to avoid the heading keep returning -1.000000, not JUST run startUpdatingHeading but run startUpdatingLocation together, this helps.
Try using this...
CLLocationManager *locationManager = [[CLLocationManager alloc] init];
locationManager.delegate=self;
locationManager.desiredAccuracy=kCLLocationAccuracyBestForNavigation;
// Start heading updates.
if (locationManager.headingAvailable && locationManager.locationServicesEnabled)
{
locationManager.headingFilter = kCLHeadingFilterNone;
[locationManager startUpdatingHeading];
}
and after doing this CLLocationManager delegate methods calls
- (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading {
// Use the true heading if it is valid.
[lblAccuracy setText:[NSString stringWithFormat:#"%.1fmi",newHeading.headingAccuracy]];
}
But this coding works on device not in simulator...
Happy coding..
---My Solution---
What I did was, add in the [self.locationManager startUpdatingLocation] to before or after the [self.locationManager startUpdatingHeading]; (when Location Services is off & re-enable from the Settings). I'm not sure this is a good solution, but this is what I did to make it work, if you have any better solution please share.
I had some trouble with the location manager myself and found out that for me it helped to unplug the iPhone from the computer when testing. Somehow the calibration alert only popped up after unplugging the iPhone.
I had this same problem. I moved startUpdatingHeading into a button action, then moved it back to where the CLLocationManager is allocated -- where it had been working fine -- and it started returning only -1.
I rebooted my iPad and it started working again. Hopefully it stays that way.
Edit: Nope, it didn't stay that way. I had to use startUpdatingLocation too. Won't this wear down the battery though? I set desiredAccuracy to kCLLocationAccuracyThreeKilometers, because I am not using location data anyway.
A TRUE reading requires knowing the magnetic variation for the place where you are using the compass. From the previous discussion, it appears to be that the function that corrects the true direction from magnetic direction needs your location for obtaining the variation value. If you don't like to use the location GPS information in your code, I suggest reading the magnetic reading and correct the value by yourself. You need to obtain the variation for the desired location first then apply the following formula: T=M ± V, where T is the true direction, M is the compass magnetic reading and V is the variation. Use "+" for East and "-" for West. I found the allowing web site provide the variation(magnetic declination) for any needed location: http://www.geomag.nrcan.gc.ca/calc/mdcal-eng.php.
When location services are off, the didUpdateHeading delegate method returns only the magnetic heading. You can use it according to your needs. According to Apple docs..
To begin the delivery of heading-related events, assign a delegate to
the location manager object and call its startUpdatingHeading method.
If location updates are also enabled, the location manager returns
both the true heading and magnetic heading values. If location updates
are not enabled, the location manager returns only the magnetic
heading value.
Working on this problem now. I can get updates from Core Motion when I use SpriteKit. It's about being able to call a function continuously like once a frame (1/60th of a second) or every few frames. Without using SpriteKit, the documentation says to invoke the updates within a closure, which I assume will be on their own thread and up to you to release.
There's an algorithm for converting the magnetometer readings to actual degrees relative to true north. Picture a graph that looks like the time domain function of alternating current and you'll see that interpolating the data is a simple matter of applying Maxwell's equations. Here's an example on honeywell
Can the iPhone SDK take advantage of the iPhone's proximity sensors? If so, why hasn't anyone taken advantage of them? I could picture a few decent uses.
For example, in a racing game, you could put your finger on the proximity sensor to go instead of taking up screen real-estate with your thumb. Of course though, if this was your only option, then iPod touch users wouldn't be able to use the application.
Does the proximity sensor tell how close you are, or just that something is in front of it?
There is a public API for this. -[UIApplication setProximitySensingEnabled:(BOOL)] will turn the feature on. BTW, it doesn't seem to be using the light sensor, because proximity sensing would tweak out in a dark room.
However, the API call basically blanks the screen when you hold the phone up to your face. Not useful for interaction, sadly.
Assuming you mean the sensor that shuts off the screen when you hold it to your ear, I'm pretty sure that is just an infrared sensor inside the ear speaker. If you start the phone app (you don't have to be making a call) and hold something to cast a shadow over the ear speaker, you can make the display shut off.
When you asked this question it was not accessible via the public API. You can now access the sensor's state via UIDevice's proximityState property. However, it wouldn't be that useful for games, since it is only an on/off thing, not a near/far measure. Plus, it's only available on the iPhone and not the iPod touch.
Evidently the proximity sensor will never turn on if the status bar is in landscape orientation.
i.e, if you call:
[UIApplication sharedApplication].statusBarOrientation = UIInterfaceOrientationLandscapeLeft;
You will no longer get the proximity:ON notifications.
This definitely happens on OS 3.0, I can't test it on a 2.X device since I don't have one with a proximity sensor.
This seems like a bug.
The proximity sensor works via measuring IR reflectance. If you hold the iPhone up to a webcam, you can see a small, pulsing IR LED.
There's a lot of confusion between the proximity sensor and the ambient light sensor. The iPhone has both. The Touch does not have a proximity sensor, making it a poor choice for user input. It would be a bad idea anyway since Apple isn't obligated to locate it in the same place in future devices; you aren't supposed to know or care where it is.
The proximity sensor works by pulsing an infrared LED and measuring the amount of reflectance. You can see this using your iSight camera (most digital cameras are sensitive to IR.) Just launch Photo Booth, initiate a call (or play a voicemail) on the phone and point it at your iSight camera. Note the flashing light next to the earpiece; cover it with your finger and the screen will go black.
The ambient light sensor's API is evidently private at this point.
Just to update, this is possible.
device = [UIDevice currentDevice];
// Turn on proximity monitoring
[device setProximityMonitoringEnabled:YES];
// To determine if proximity monitoring is available, attempt to enable it.
// If the value of the proximityMonitoringEnabled property remains NO, proximity
// monitoring is not available.
// Detect whether device supports proximity monitoring
proxySupported = [device isProximityMonitoringEnabled];
// Register for proximity notifications
[notificationCenter addObserver:self selector:#selector(proximityChanged:) name:UIDeviceProximityStateDidChangeNotification object:device];
As benzado points out, you can use:
// Returns a BOOL, YES if device is proximate
[device proximityState];
There is no public API for this.
In iPhone 3.0 there is official support for the proximity sensor. Have a look at UIDevice proximityMonitoringEnabled in the docs.
If you aren't aiming for the AppStore, you can read my articles here on getting access to those:
Proximity Sensor: http://iphonedevwiki.net/index.php/AppleProxShim
Ambient Light Sensor: http://iphonedevwiki.net/index.php/AppleISL29003
Evidently the proximity sensor will never turn on if the status bar is in landscape orientation.
i.e. if you call:
[UIApplication sharedApplication].statusBarOrientation = UIInterfaceOrientationLandscapeLeft;
You will no longer get proximity:ON notifications.
This definitely happens on OS 3.0, I can't test it on a 2.X device since I don't have one with a proximity sensor.
This seems like a bug.
answered Jul 22 '09 at 5:49
Kevin Lambert
I've encoutered this problem too. It took me a long time to figure out the real reason of why the proximity sensor is not working. When orientation is UIInterfaceOrientationLandscapeLeft or UIInterfaceOrientationLandscapeRight, proximity sensor does not work; while in portrait mode it works well. My iPhone is iPhone 4S (iOS SDK 5.0).
Those proximity sensors are basically a matrix of conductors. The vertical "wires" are tracks on one side of a thin sheet of insulator, the horizontal ones are on the other side. The intersections function as capacitors. Your finger carries an electrostatic charge, so capacitance of each junction varies with proximity. FETs amplify the signal and biasing sets a threshold. In practice the circuit is more complex than that because it has to detect a relative change and reject noise.
But anyway, what the sensor grid tells you is that a field effect has been sensed, and that field effect is characteristic of object about the size of a fingertip and resting on the surface of the display. The centroid of the capacitive disturbance is computed (probably by hardware) and the coordinates are (presumably) reported as numbers on a port most likely brought to the attention of the device OS by an interrupt. In something as sexy as an iPhone there's probably a buffer of the last dozen or so positions so it can work out direction and speed. Probably these are also computed by hardware and presented as numbers on the same port.
#Dipak Patel & #Coderer
You can download working code at
http://spazout.com/google_cheats_independent_iphone_developers_screwed
It has a working implementation of proximityStateChanged a undocumented method in UIApplication.
Hope this helps.
To turn the screen off it's conceivable that more than one sensors is used to figure out if the screen should be turned off or not. The IR proximity sensor described by Cryptognome in conjunction with the Touch screen sensor described by Peter Wone could work out if the iphone is being held close to your face (or something else with a slight electric charge) or if its just very close to something in-animate.