Question

I have got CLLocation object which contains current location of user and I have got 4 lat/long pairs for each corner of a rectangle which can be angled. Now I want to check whether CLLocation coordinates are within that rectangle.

Following are the coordinates of the rectangle

#define NorthEast_LAT 51.514894
#define NorthEast_LNG -0.135306
#define SouthEast_LAT 51.514831
#define SouthEast_LNG -0.135153
#define NorthWest_LAT 51.514719
#define NorthWest_LNG -0.135858
#define SouthWest_LAT 51.514556
#define SouthWest_LNG -0.135714

I have tried following code but I think it will only work when angle of rectangle is 0 deg.

 BOOL withinRect = [delegate.CLController latlngWithInBox:location 
                                                    point1:CLLocationCoordinate2DMake(NorthEast_LAT, NorthEast_LNG) 
                                                    point2:CLLocationCoordinate2DMake(SouthEast_LAT, SouthEast_LNG) 
                                                    point3:CLLocationCoordinate2DMake(NorthWest_LAT, NorthWest_LNG)
                                                    point4:CLLocationCoordinate2DMake(SouthWest_LAT, SouthWest_LNG)];

 - (BOOL) latlngWithInBox:(CLLocation *)position point1:(CLLocationCoordinate2D)point1 point2:(CLLocationCoordinate2D)point2 point3:(CLLocationCoordinate2D)point3 point4:(CLLocationCoordinate2D)point4 {

if (position.coordinate.latitude >= point3.latitude && position.coordinate.latitude <= point2.latitude
    && position.coordinate.longitude >= point3.longitude && position.coordinate.longitude <= point2.longitude) {
    return YES;
}
return NO;

}

Answer 1

- (BOOL) latlngWithInBox:(CLLocation *)position point1:(CLLocationCoordinate2D)point1 point2:(CLLocationCoordinate2D)point2 point3:(CLLocationCoordinate2D)point3 point4:(CLLocationCoordinate2D)point4 {
    //&& position.coordinate.latitude >= [[point4 objectAtIndex:0] floatValue] && position.coordinate.latitude <= [[point1 objectAtIndex:0] floatValue] && position.coordinate.longitude <= [[point4 objectAtIndex:1] floatValue] && position.coordinate.longitude >= [[point1 objectAtIndex:1] floatValue]
    if (PointInTriangle(position.coordinate, point1, point2, point3) || PointInTriangle(position.coordinate, point2, point3, point4)) {
        return YES;
    }
    return NO;
}

float sign(CLLocationCoordinate2D p1, CLLocationCoordinate2D p2, CLLocationCoordinate2D p3)
{
    return (p1.longitude - p3.longitude) * (p2.latitude - p3.latitude) - (p2.longitude - p3.longitude) * (p1.latitude - p3.latitude);
}

bool PointInTriangle(CLLocationCoordinate2D pt, CLLocationCoordinate2D v1, CLLocationCoordinate2D v2, CLLocationCoordinate2D v3)
{
    bool b1, b2, b3;

    b1 = sign(pt, v1, v2) < 0.0f;
    b2 = sign(pt, v2, v3) < 0.0f;
    b3 = sign(pt, v3, v1) < 0.0f;

//    NSLog(@"b1-%@", [NSNumber numberWithBool:b1]);
//    NSLog(@"b2-%@", [NSNumber numberWithBool:b2]);
//    NSLog(@"b3-%@", [NSNumber numberWithBool:b3]);

    return ((b1 == b2) && (b2 == b3));
}