Unable to draw MKPolylineView crossing longitude +/-180

Question

I\'m having a problem drawing an MKPolylineView on an MKMapView. The line represents a trip around the world, which begins and ends near New York, always traveling east. O

Answer 1

This seems to be a limitation of the MKMapView.

A workaround is to split the +/-180 crossing into "east" and "west" parts.

For an around-the-world trip (finish == start), you can put the "west" part of the crossing at the front of the polyline.
For example:

CLLocationCoordinate2D newYorkCoord = CLLocationCoordinate2DMake(40.7141667, -74.0063889);
CLLocationCoordinate2D londonCoord = CLLocationCoordinate2DMake(51.5, -0.116667);
CLLocationCoordinate2D japanCoord = CLLocationCoordinate2DMake(36, 138);
CLLocationCoordinate2D sanFranciscoCoord = CLLocationCoordinate2DMake(37.775, -122.4183333);

CLLocationCoordinate2D japanToSFMidpointEast;
//use average calc as crude way to find midpoint...
japanToSFMidpointEast.latitude = (japanCoord.latitude + sanFranciscoCoord.latitude)/2.0;
japanToSFMidpointEast.longitude = 180;

CLLocationCoordinate2D japanToSFMidpointWest;
japanToSFMidpointWest.latitude = japanToSFMidpointEast.latitude;
japanToSFMidpointWest.longitude = -180;

int pointsCount = 6;
CLLocationCoordinate2D *points = malloc(pointsCount * sizeof(CLLocationCoordinate2D));
points[0] = japanToSFMidpointWest;
points[1] = sanFranciscoCoord;
points[2] = newYorkCoord;
points[3] = londonCoord;
points[4] = japanCoord;
points[5] = japanToSFMidpointEast;
MKPolyline *polyline = [MKPolyline polylineWithCoordinates:points count:pointsCount];
[mapView addOverlay:polyline];
free(points);
points = NULL;

If a trip is not around-the-world (finish != start), you'll have to use two polylines.
This example goes from Japan to SF:

CLLocationCoordinate2D japanCoord = CLLocationCoordinate2DMake(36, 138);
CLLocationCoordinate2D sanFranciscoCoord = CLLocationCoordinate2DMake(37.775, -122.4183333);

CLLocationCoordinate2D japanToSFMidpointEast;
japanToSFMidpointEast.latitude = (japanCoord.latitude + sanFranciscoCoord.latitude)/2.0;
japanToSFMidpointEast.longitude = 180;

CLLocationCoordinate2D japanToSFMidpointWest;
japanToSFMidpointWest.latitude = japanToSFMidpointEast.latitude;
japanToSFMidpointWest.longitude = -180;

int eastPointsCount = 2;
CLLocationCoordinate2D *eastPoints = malloc(eastPointsCount * sizeof(CLLocationCoordinate2D));
eastPoints[0] = japanCoord;
eastPoints[1] = japanToSFMidpointEast;
MKPolyline *eastPolyline = [MKPolyline polylineWithCoordinates:eastPoints count:eastPointsCount];
[mapView addOverlay:eastPolyline];
free(eastPoints);
eastPoints = NULL;

int westPointsCount = 2;
CLLocationCoordinate2D *westPoints = malloc(westPointsCount * sizeof(CLLocationCoordinate2D));
westPoints[0] = japanToSFMidpointWest;
westPoints[1] = sanFranciscoCoord;
MKPolyline *westPolyline = [MKPolyline polylineWithCoordinates:westPoints count:westPointsCount];
[mapView addOverlay:westPolyline];
free(westPoints);
westPoints = NULL;