How to calculate the center coordinates of CLLocat

问题:

I want calculate the center point between my location and some annotation. So far I have done this:

CLLocation *myLoc = self.locMgr.location;

        MKPointAnnotation *middleAnnotation = [locationV.annotations objectAtIndex:locationV.annotations.count/2];

        CLLocation *someStuiodLoc = [[CLLocation alloc] initWithLatitude:middleAnnotation.coordinate.latitude longitude:middleAnnotation.coordinate.longitude];

        CLLocationDistance dist = [myLoc distanceFromLocation:someStuiodLoc];

How can I calculate the center point/cordinate of "dist" ??

回答1:

#define ToRadian(x) ((x) * M_PI/180)
#define ToDegrees(x) ((x) * 180/M_PI)

+ (CLLocationCoordinate2D)midpointBetweenCoordinate:(CLLocationCoordinate2D)c1 andCoordinate:(CLLocationCoordinate2D)c2 
{ 
          c1.latitude = ToRadian(c1.latitude); 
          c2.latitude = ToRadian(c2.latitude);
          CLLocationDegrees dLon = ToRadian(c2.longitude - c1.longitude); 
          CLLocationDegrees bx = cos(c2.latitude) * cos(dLon); 
          CLLocationDegrees by = cos(c2.latitude) * sin(dLon);
          CLLocationDegrees latitude = atan2(sin(c1.latitude) + sin(c2.latitude), sqrt((cos(c1.latitude) + bx) * (cos(c1.latitude) + bx) + by*by));
          CLLocationDegrees longitude = ToRadian(c1.longitude) + atan2(by, cos(c1.latitude) + bx);

           CLLocationCoordinate2D midpointCoordinate; 
           midpointCoordinate.longitude = ToDegrees(longitude); 
           midpointCoordinate.latitude = ToDegrees(latitude);

           return midpointCoordinate;
}

回答2:

U can calculate the midPoint of two coordinates using the mid point formula (http://www.purplemath.com/modules/midpoint.htm) which gives a close approximation to the actual geographical point if the distances are lesser than 500 miles. If you consider that the earth is spherical, then a more complex treatment of the points would be involved.

回答3:

I have written library function in Swift to calculate the midpoint between multiple coordinates as following:

//        /** Degrees to Radian **/

class func degreeToRadian(angle:CLLocationDegrees) -> CGFloat{

    return (  (CGFloat(angle)) / 180.0 * CGFloat(M_PI)  )

}

//        /** Radians to Degrees **/

class func radianToDegree(radian:CGFloat) -> CLLocationDegrees{

    return CLLocationDegrees(  radian * CGFloat(180.0 / M_PI)  )

}

class func middlePointOfListMarkers(listCoords: [CLLocationCoordinate2D]) -> CLLocationCoordinate2D{

    var x = 0.0 as CGFloat

    var y = 0.0 as CGFloat

    var z = 0.0 as CGFloat



    for coordinate in listCoords{

        var lat:CGFloat = degreeToRadian(coordinate.latitude)

        var lon:CGFloat = degreeToRadian(coordinate.longitude)

        x = x + cos(lat) * cos(lon)

        y = y + cos(lat) * sin(lon);

        z = z + sin(lat);

    }

    x = x/CGFloat(listCoords.count)

    y = y/CGFloat(listCoords.count)

    z = z/CGFloat(listCoords.count)



    var resultLon: CGFloat = atan2(y, x)

    var resultHyp: CGFloat = sqrt(x*x+y*y)

    var resultLat:CGFloat = atan2(z, resultHyp)



    var newLat = radianToDegree(resultLat)

    var newLon = radianToDegree(resultLon)

    var result:CLLocationCoordinate2D = CLLocationCoordinate2D(latitude: newLat, longitude: newLon)

    return result

}

Detailed answer can be found here