Google Maps iOS SDK: How do I get accurate latitude and longitude coordinates from a camera's visibleRegion?

Question

EDIT: This is now a confirmed bug with this SDK

I\'m using version 1.1.1.2311 of the Google Maps for iOS SDK, and I\'m looking to find the bounding latitude and long

Answer 1

Looks like the latitude and longitude coordinates you are printing out and manually plotting are possibly off a bit / being truncated. %f defaults to only print out to 6 decimal places.

Here's a related question that might help:

How to print a double with full precision on iOS?

Answer 2

Maybe you give the location Manager the wrong accuracy..

Try to increase it:

locationMgr.desiredAccuracy = kCLLocationAccuracyBest;

The battery is draining moreyy

Answer 3

The solution is to download the latest version of the SDK (1.2 at the time of this writing) as the issue has been fixed.

From the 1.2 release notes:

Resolved Issues: - visibleRegion now reports correctly sized region on Retina devices

Download here.

Answer 4

I saw your issue here. Hope that they fix this issue in next update.

But now we can take the real visible region like this:

    CGPoint topLeftPoint = CGPointMake(0, 0);
    CLLocationCoordinate2D topLeftLocation =
    [_mapView.projection coordinateForPoint: topLeftPoint];

    CGPoint bottomRightPoint =
    CGPointMake(_mapView.frame.size.width, _mapView.frame.size.height);
    CLLocationCoordinate2D bottomRightLocation =
    [_mapView.projection coordinateForPoint: bottomRightPoint];

    CGPoint topRightPoint = CGPointMake(_mapView.frame.size.width, 0);
    CLLocationCoordinate2D topRightLocation =
    [_mapView.projection coordinateForPoint: topRightPoint];

    CGPoint bottomLeftPoint =
    CGPointMake(0, _mapView.frame.size.height);
    CLLocationCoordinate2D bottomLeftLocation =
    [_mapView.projection coordinateForPoint: bottomLeftPoint];

    GMSVisibleRegion realVisibleRegion;
    realVisibleRegion.farLeft = topLeftLocation;
    realVisibleRegion.farRight = topRightLocation;
    realVisibleRegion.nearLeft = bottomLeftLocation;
    realVisibleRegion.nearRight = bottomRightLocation;

    [self drawPolylineWithGMSVisibleRegion:realVisibleRegion color:[UIColor redColor] width:10.0f forMap:mapView];

Drawing polyline method:

- (void)drawPolylineWithGMSVisibleRegion:(GMSVisibleRegion)visibleRegion
                               color:(UIColor*)color
                               width:(double)width
                              forMap:(GMSMapView*)mapView{
    GMSPolylineOptions *rectangle = [GMSPolylineOptions options];
    rectangle.color = color;
    rectangle.width = width;
    GMSMutablePath *path = [GMSMutablePath path];
    [path addCoordinate:visibleRegion.nearRight];
    [path addCoordinate:visibleRegion.nearLeft];
    [path addCoordinate:visibleRegion.farLeft];
    [path addCoordinate:visibleRegion.farRight];
    [path addCoordinate:visibleRegion.nearRight];
    rectangle.path = path;
    [mapView addPolylineWithOptions:rectangle];
}

It works even for map with non-default bearing and angle.

Answer 5

To get the bounding latitude and longitude you have to do the following steps:

GMSCoordinateBounds *bounds = [[GMSCoordinateBounds alloc] initWithRegion:self.googleMapsView.projection.visibleRegion];

CLLocationCoordinate2D northEast = bounds.northEast;
CLLocationCoordinate2D northWest = CLLocationCoordinate2DMake(bounds.northEast.latitude, bounds.southWest.longitude);
CLLocationCoordinate2D southEast = CLLocationCoordinate2DMake(bounds.southWest.latitude, bounds.northEast.longitude);
CLLocationCoordinate2D southWest = bounds.southWest;

Best regards Robert