Encode polyline. Google Maps API v3 algorithm. Objective c.

EncodePolyline

+ (NSString *)encodeStringWithCoordinates:(NSArray *)coordinates
{
  NSMutableString *encodedString = [NSMutableString string];
  int val = 0;
  int value = 0;
  CLLocationCoordinate2D prevCoordinate = CLLocationCoordinate2DMake(0, 0);
  
  for (NSValue *coordinateValue in coordinates) {
    CLLocationCoordinate2D coordinate = [coordinateValue MKCoordinateValue];
    
    // Encode latitude
    val = round((coordinate.latitude - prevCoordinate.latitude) * 1e5);
    val = (val < 0) ? ~(val<<1) : (val <<1);
    while (val >= 0x20) {
      int value = (0x20|(val & 31)) + 63;
      [encodedString appendFormat:@"%c", value];
      val >>= 5;
    }
    [encodedString appendFormat:@"%c", val + 63];
    
    // Encode longitude
    val = round((coordinate.longitude - prevCoordinate.longitude) * 1e5);
    val = (val < 0) ? ~(val<<1) : (val <<1);
    while (val >= 0x20) {
      value = (0x20|(val & 31)) + 63;
      [encodedString appendFormat:@"%c", value];
      val >>= 5;
    }
    [encodedString appendFormat:@"%c", val + 63];
    
    prevCoordinate = coordinate;
  }
  
  return encodedString;
}

// You call it with
[... encodeStringWithCoordinates:@[
                      [NSValue valueWithMKCoordinate:CLLocationCoordinate2DMake(38.5, -120.2)],
                      [NSValue valueWithMKCoordinate:CLLocationCoordinate2DMake(40.7, -120.95)],
                      [NSValue valueWithMKCoordinate:CLLocationCoordinate2DMake(43.252, -126.453)]
                      ]