fit to zoom in maps on iphone

Question

I am currently working on google maps.Using the GPS, I obtain the user's lat long information and hit a web service to obtain the nearest 5 stores available. I am able to plot the pins for it but the problem is how to fit the 5 pins to a maximum zoom scale ? I mean how does one obtain the latitude and longitude delta of the span in order to zoom as well as fit all the pins at the same time?

Edited my answer to include example and annotation class for clarity — Simon, Aug 25 '11 at 06:46

score 1 · Answer 1 · answered Aug 25 '11 at 06:46

Try the following...

    -(void)zoomToFitMapAnnotations:(MKMapView*)mapView
    {
        if([mapView.annotations count] == 0)
            return;

        CLLocationCoordinate2D topLeftCoord;
        topLeftCoord.latitude = -90;
        topLeftCoord.longitude = 180;

        CLLocationCoordinate2D bottomRightCoord;
        bottomRightCoord.latitude = 90;
        bottomRightCoord.longitude = -180;

        for(DisplayMap* annotation in mapView.annotations)
        {
            topLeftCoord.longitude = fmin(topLeftCoord.longitude, annotation.coordinate.longitude);
            topLeftCoord.latitude = fmax(topLeftCoord.latitude, annotation.coordinate.latitude);

            bottomRightCoord.longitude = fmax(bottomRightCoord.longitude, annotation.coordinate.longitude);
            bottomRightCoord.latitude = fmin(bottomRightCoord.latitude, annotation.coordinate.latitude);
        }   
        MKCoordinateRegion region;
        region.center.latitude = topLeftCoord.latitude - (topLeftCoord.latitude - bottomRightCoord.latitude) * 0.5;
        region.center.longitude = topLeftCoord.longitude + (bottomRightCoord.longitude - topLeftCoord.longitude) * 0.5;
        region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * 1.1; 
        region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * 1.1;                         

        region = [mapView regionThatFits:region];
        [mapView setRegion:region animated:YES];
    }

score 0 · Answer 2 · edited May 23 '17 at 11:55

There is a good post on how to do this here

The finished code I used to achieve this is here...

-(void)zoomToFitMapAnnotations:(MKMapView*)mv
{
    if([mv.annotations count] == 0)
        return;

    CLLocationCoordinate2D topLeftCoord;
    topLeftCoord.latitude = -90;
    topLeftCoord.longitude = 180;

    CLLocationCoordinate2D bottomRightCoord;
    bottomRightCoord.latitude = 90;
    bottomRightCoord.longitude = -180;

    for(MapViewAnnotate* annotation in mv.annotations)
    {
        topLeftCoord.longitude = fmin(topLeftCoord.longitude, annotation.coordinate.longitude);
        topLeftCoord.latitude = fmax(topLeftCoord.latitude, annotation.coordinate.latitude);

        bottomRightCoord.longitude = fmax(bottomRightCoord.longitude, annotation.coordinate.longitude);
        bottomRightCoord.latitude = fmin(bottomRightCoord.latitude, annotation.coordinate.latitude);
    }

    MKCoordinateRegion region;
    region.center.latitude = topLeftCoord.latitude - (topLeftCoord.latitude - bottomRightCoord.latitude) * 0.5;
    region.center.longitude = topLeftCoord.longitude + (bottomRightCoord.longitude - topLeftCoord.longitude) * 0.5;
    region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * 1.1; // Add a little extra space on the sides
    region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * 1.1; // Add a little extra space on the sides

    region = [mv regionThatFits:region];
    [mv setRegion:region animated:YES];
}

This assumes you're using annotation objects in from an annotation class similar to this (stored in an array)....

MapViewAnnotate.h

@interface MapViewAnnotate : NSObject <MKAnnotation>
{
NSString *title;
NSString *subtitle;
CLLocationCoordinate2D coordinate;
}

@property (nonatomic, copy) NSString *title;
@property (nonatomic, copy) NSString *subtitle;
@property (nonatomic, readonly) CLLocationCoordinate2D coordinate;

- (id)initWithCoordinate:(CLLocationCoordinate2D)c title:(NSString *)t subtitle:(NSString *)s;

@end

MapViewAnnotate.m

#import "PropertyMapViewAnnotate.h"

@implementation MapViewAnnotate

@synthesize coordinate, title, subtitle;

- (id)initWithCoordinate:(CLLocationCoordinate2D)c title:(NSString *)t subtitle:(NSString *)s
{
[super init];
coordinate = c;
[self setTitle:t];
[self setSubtitle:s];
return self;
}

- (void)dealloc
{
[title release];
[subtitle release];
[super dealloc];
}

@end

fit to zoom in maps on iphone

2 Answers2