CLLocation speed

Question

Hi guys.

I am developing GPS application. Do you know about how to detect speed of mobile device ?

Actually, I need to detect the speed every 2 seconds.

I know didUpdateToLocation method is called when location changed.

• (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation

But I think this method is not suitable for my issue.

So, Do I need to check speed of [CLLocationManager location] in 2 seconds ?

Any suggestion ?

Thanks in advance.

Answer 1

Hi there,

You can only really use the delegate method you have suggested in your question.

Even if you access the [CLLocationManager location] every 2 seconds, you will only receive the coordinate you last received in the delegate method above.

Why the need to poll every two seconds? The iphone can update it's coordinates in less time on some cases.

HTH

Answer 2

Thanks for your response.

I am searching about to detect the speed.

didUpdateToLocation is invoked only by changed location.

If location is not changed, speed must be 0.

So, I need to poll every 2 seconds.

Do you have sample code related getting speed ?

Can you share the knowledge ?

Thanks in advance.

Answer 3

How about the code below which works from the delegate method. Alternatively, if you did want to poll, then keep your previous location and check the distance changed from the last poll and use the manual method (also shown below) to calculate the speed.

Speed is calculated/provided in m/s so multiply by 3.6 for kph or 2.23693629 for mph.

-(void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
   //simply get the speed provided by the phone from newLocation
    double gpsSpeed = newLocation.speed;

    // alternative manual method
    if(oldLocation != nil)
    {
    CLLocationDistance distanceChange = [newLocation getDistanceFrom:oldLocation];
        NSTimeInterval sinceLastUpdate = [newLocation.timestamp timeIntervalSinceDate:oldLocation.timestamp];
        double calculatedSpeed = distanceChange / sinceLastUpdate;

    }

}