iOS Core Location GPS Tutorial pt.2

Published on August 18th, 2010 in iPhone Code Snippets & Tutorials, iPhone Programming

In this tutorial we will expand on the previous Core Location tutorial. Here we will extract specific location attributes such as coordinates, altitude, and speed.

The CLLocation object contains several properties containing location details. These properties are:

altitude – type CLLocationDistance

coordinate – type CLLocationCoordinate2D

course – type CLLocationDirection

horizontalAccuracy – type CLLocationAccuracy

speed – type CLLocationSpeed

timestamp – type NSDate

verticalAccuracy – type CLLocationAccuracy

A quick look in CLLocation.h reveals several typedefs which should help you understand how to handle the data:

typedef double CLLocationAccuracy;
typedef double CLLocationSpeed;
typedef double CLLocationDirection;
typedef double CLLocationDistance;
typedef double CLLocationDegrees;
typedef struct {
	CLLocationDegrees latitude;
	CLLocationDegrees longitude;
} CLLocationCoordinate2D;

Just a bunch of doubles and a structure containing doubles.

This tutorial will focus on three of the above properties; coordinate, speed, and altitude.

Start by opening up the project in the previous tutorial. Compile and run on your iPhone to make sure everything works with your version of the SDK and device. Once that’s done, open up CoreLocationDemoViewController.h, remove the current IBOutlet and add four new IBOutlets of type UILabel for speed, latitude, longitude, and altitude.

@interface CoreLocationDemoViewController : UIViewController <CoreLocationControllerDelegate> {
	CoreLocationController *CLController;
	IBOutlet UILabel *speedLabel;
	IBOutlet UILabel *latitudeLabel;
	IBOutlet UILabel *longitudeLabel;
	IBOutlet UILabel *altitudeLabel;
}

Open up CoreLocationDemoViewController.xib and delete the current UILabel. Create four new ones and link them up to the IBOutlets we just created. You can save and quit Interface Builder when you are done.

Open CoreLocationDemoViewController.m and clear the contents of locationUpdate: and locationError: and add the following code:

- (void)locationUpdate:(CLLocation *)location {
	speedLabel.text = [NSString stringWithFormat:@"SPEED: %f", [location speed]];
	latitudeLabel.text = [NSString stringWithFormat:@"LATITUDE: %f", location.coordinate.latitude];
	longitudeLabel.text = [NSString stringWithFormat:@"LONGITUDE: %f", location.coordinate.longitude];
	altitudeLabel.text = [NSString stringWithFormat:@"ALTITUDE: %f", [location altitude]];
}
 
- (void)locationError:(NSError *)error {
	speedLabel.text = [error description];
}

We simply set the UILabel text to a NSString containing the value of the given property.

For more information on CLLocation properties, visit Apple’s developer documentation page at:
http://developer.apple.com/iphone/library/documentation/CoreLocation/Reference/CLLocation_Class/CLLocation/CLLocation.html

[Demo Project Source: Core Location GPS Demo - 25k]
[Demo Project Source: Core Location GPS Demo Part 2 - 25k]

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Tags: code, compass, core, corelocation, Development, gps, ios, iPhone, location, open, programming

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Comments

35 Responses to “iOS Core Location GPS Tutorial pt.2”

iOS Core Location GPS Tutorial pt.1 « iPhone Open Source - Nick Vellios says:

August 19, 2010 at 5:54 pm

[...] Click here for iOS Core Location GPS Tutorial Part 2 [...]
Dale says:

August 21, 2010 at 12:26 pm

Wow this is a great resource.. I’m enjoying it.. good article
Request a tutorial « iPhone Open Source - Nick Vellios says:

August 21, 2010 at 4:32 pm

[...] Core Location GPS Tutorial Part 1 Core Location GPS Tutorial Part 2 [...]

manju says:

September 6, 2010 at 12:10 pm

This the code i write below

#import 
#import 
 
@interface Trackview : UIView {
	IBOutlet UIView *pview2;
	IBOutlet UIView *trackview;
	IBOutlet UIBarButtonItem *TrackStart;
	CLLocationManager *MYlocation;
	IBOutlet UILabel *speedLabel;
	IBOutlet UILabel *latitudeLabel;
	IBOutlet UILabel *longitudeLabel;
	IBOutlet UILabel *altitudeLabel;
}
@property (nonatomic, retain) CLLocationManager *MYlocation; 
-(IBAction)trackstart:(id)sender;
- (void)locationManager:(CLLocationManager *)manager
	didUpdateToLocation:(CLLocation *)newLocation
		   fromLocation:(CLLocation *)oldLocation;
@end
 
#import "Trackview.h"
 
@implementation Trackview
@synthesize MYlocation;
 
- (id)initWithFrame:(CGRect)frame {
    if ((self = [super initWithFrame:frame])) {
        // Initialization code
		 // send loc updates to myself
 
	}
    return self;
}
 
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
	[UIView beginAnimations:Nil context:NULL]; 
	[UIView setAnimationDuration:1.0];		
	[UIView setAnimationTransition:UIViewAnimationTransitionNone forView:self cache:YES];  
	[trackview removeFromSuperview];
	[self addSubview:pview2];
	[UIView commitAnimations];
}
 
-(IBAction)trackstart:(id)sender{
		self.MYlocation = [[CLLocationManager alloc]init];
		NSLog (@"$$$$$$$$$$$$$$%@",MYlocation);
		MYlocation.delegate = self;
		NSLog (@"$$$$$$$$$$$$$$%@",MYlocation.delegate);
		MYlocation.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
		MYlocation.distanceFilter = kCLDistanceFilterNone;		
		[MYlocation startUpdatingLocation]; 
 
}
 
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
	if([self conformsToProtocol:@protocol(CLLocationManagerDelegate)]) {  // Check if the class assigning itself as the delegate conforms to our protocol.  If not, the message will go nowhere.  Not good.
		[self locationUpdate:newLocation];
	}
}
 
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error {
	if([self conformsToProtocol:@protocol(CLLocationManagerDelegate)]) {  // Check if the class assigning itself as the delegate conforms to our protocol.  If not, the message will go nowhere.  Not good.
		[self locationError:error];
	}
}
 
- (void)locationUpdate:(CLLocation *)location {
	speedLabel.text = [NSString stringWithFormat:@"SPEED: %f", [location speed]];
	latitudeLabel.text = [NSString stringWithFormat:@"LATITUDE: %f", location.coordinate.latitude];
	longitudeLabel.text = [NSString stringWithFormat:@"LONGITUDE: %f", location.coordinate.longitude];
	altitudeLabel.text = [NSString stringWithFormat:@"ALTITUDE: %f", [location altitude]];
}
 
- (void)locationError:(NSError *)error {
	speedLabel.text = [error description];
}
 
- (void)dealloc {
	[self.MYlocation release];
	[super dealloc];
}
 
@end

The error is show like this

ERROR,Time,305491182.961,Function,”void CLClientHandleDaemonDataRegistration(__CLClient*, mach_port_t, const CLDaemonCommToClientRegistration*, const __CFDictionary*)”,server did not accept client registration 2
ERROR,Time,305491183.102,Function,”void CLClientHandleDaemonDataRegistration(__CLClient*, mach_port_t, const CLDaemonCommToClientRegistration*, const __CFDictionary*)”,server did not accept client registration 2

please help me out to solve the problem
Thank you

Nick Vellios says:

September 6, 2010 at 12:18 pm

manju, you need to click “Allow” when iOS asks if the app can use your current location. That is the problem. You can use [CLLocationManager locationServicesEnabled] to check if location services are enabled to prevent an error if someone clicks “Don’t Allow” when the app launches.

There may also be some issues with running in the simulator. Try on an actual device.

Are you using this on a GPS enabled device?
manju says:

September 6, 2010 at 1:26 pm

i put [CLLocationManager locationServicesEnabled] this line of code above this ” [MYlocation startUpdatingLocation]; ” line but it not work .

i am checking in the simulator 4.0but i download u code and run int the simulator it work correctly.

When i run my code i copped above code it give the the after compiling [MYlocation startUpdatingLocation]; this line it show the error

ERROR,Time,305491182.961,Function,”void CLClientHandleDaemonDataRegistration(__CLClient*, mach_port_t, const CLDaemonCommToClientRegistration*, const __CFDictionary*)”,server did not accept client registration 2
ERROR,Time,305491183.102,Function,”void CLClientHandleDaemonDataRegistration(__CLClient*, mach_port_t, const CLDaemonCommToClientRegistration*, const __CFDictionary*)”,server did not accept client registration 2
Nick Vellios says:

September 6, 2010 at 1:55 pm

You didn’t answer whether or not you clicked “Allow” or “Don’t Allow” when prompted. Try cleaning all targets and rebuilding. Make sure to click “Allow” when prompted. You must have clicked “Don’t Allow” at some point.
manju says:

September 6, 2010 at 2:25 pm

i am told that that prompt is not showing it showing directly this error

thanks
manju says:

September 6, 2010 at 2:26 pm

and i am also clear the targets it is not working
Nick Vellios says:

September 6, 2010 at 4:12 pm

Did you try it on a device?
manju says:

September 7, 2010 at 3:13 am

yes i try in the i phone its not working
vt says:

September 14, 2010 at 9:19 am

Thank you, this is one of the best iphone dev tutorials I’ve ever read.
manju says:

September 14, 2010 at 12:26 pm

hello Nick Vellios,

i want to find the distance between the two end point how should i get from the core location
please help me in this

thank you
Frank says:

October 6, 2010 at 6:35 am

Hello, Great example! has anyone been ablre to take this code and get the address from the lat long using mkreversegeocoder? i tried taking the current address sample from apple and combining it withthis, but am having no luck…
Michael Davis says:

October 6, 2010 at 10:54 am

In order to add a map view to this vc, having produced no errors, what could anyone see in this that prevents centering, and zooming to the defined span?

MKCoordinateRegion region;
MKCoordinateSpan span;
span.latitudeDelta=0.0039;
span.longitudeDelta=0.0034;

CLLocationCoordinate2D locationStart;

region.span=span;
region.center=locationStart;

[mapView setRegion:region animated:TRUE];
[mapView regionThatFits:region];
Greg Orek says:

October 20, 2010 at 12:35 pm

Your tutorials are so clear and detailed. Thank you for everything you provide here.
branchenbuch says:

October 21, 2010 at 6:57 pm

What a nice post. I really love reading these types or articles. I can?t wait to see what others have to say.
branchenverzeichnis says:

October 23, 2010 at 12:59 am

As a Newbie, I am always searching online for articles that can help me. Thank you
Cato says:

November 3, 2010 at 2:24 am

This was a great tutorial!
Made things much clearer than the other tutorials on location manager that I´ve seen, and really helped me understand the principles.
Aamer says:

November 7, 2010 at 12:12 am

Just skimming through your blog. It’s really well put togehter and these tutorials have been very informative for me (just getting into objc) so thank you
Drake says:

November 21, 2010 at 3:24 am

Great information! I’ve been looking for something like this for a while now. Thanks!
xcodemaddy says:

January 27, 2011 at 11:00 pm

This is nice tutorial.I hve downloaded ur source code when i run on simulator 4.it is showing error domain=KCLerrordomain code=0 “The Operation cou…”
why it is showing this error?
irfaan says:

February 13, 2011 at 10:28 pm

Simulator: 4.0
ipodTouch with iOS 3.1
Location service is ON, allowed

On all the two I get the following error: Error Domain=kCLErrorDomain Code=0 “The operation could not..”

Is there a problem with my WIFI or ipod?
BMHung says:

February 15, 2011 at 4:49 pm

Thanks. It’s very good but I wonder that why it takes time to initialize GPS in the first time? When I walk about 100meters GPS just start.
Malek says:

April 6, 2011 at 5:07 am

Hi, first of all, thank you so much for this great tutorial and specially for sharing, actually i did identically like you did, no problem but when i run i see the view with the label empty showing nothing can you help me please, thx in advance
Ellen Sundh says:

June 30, 2011 at 2:35 pm

Thanks for a great tutorial! Keep up the good work!
Jose says:

October 14, 2011 at 9:32 am

very but very good tutorial, but i am getting an error on both part one and part two. anyone came across this one?
server did not accept client registration 68
Mike says:

November 27, 2011 at 4:14 am

Thank you very much for the great tutorial – is it possible for you to explain how to format the speed string that it show km/h?

Thx a lot!
Hcm says:

December 24, 2011 at 6:36 am

Hi, sir.
Your tutorial is great, but I cannot get accurate speed on device. I think i seem to set wrong distanceFilter and desiredAccuracy.

In my project, i set them as below.

locationManager.distanceFilter = kCLDistanceFilterNone;
locationManager.desiredAccuracy = kCLLocationAccuracyBest;

Please help me!.
Niklas Agerbech says:

January 30, 2012 at 4:42 am

Hello,
thanks for this great tutorial!

I was wondering if you know any guides where you can make a audio file play, when the user enters a certain location?

I would like to develop a pod walk app for educational purposes.

greetings

Niklas
Manuel says:

February 3, 2012 at 3:15 am

Very useful! Thanks for sharing this information!
Prashant says:

February 26, 2012 at 2:11 am

Hi,the code is very helpful.
How can I modify this code so that it will run in Background continously.
Mario says:

February 29, 2012 at 5:10 am

Thank you for wonderful tutorial. How can I send my position via SMS or e-mail to a friend?
Thank you for help.
Michael says:

March 27, 2012 at 7:34 pm

Very good article!!!
I’m still rather new with obj-c
This was very helpful, THANKS!!!
Xradeon says:

March 15, 2013 at 1:38 pm

Very good tutorials. With your help I was able to do a my little first app for the app store. It’s free and it’s called Bike Dash.

Thanks!!

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