Polylines is not coming perfectly on google map in ios

Question

I am trying to draw path on google map in ios7 . For that i used json data which is provided by google map.

1. i am using google direction api and i able to draw path between two place.
2. when i am using path for near place then it is coming fine but when i am using path for long distance then path not turning with google map.
3. plz see in these image for more clear (before zoom).
4. and after zoom , it is not turning correctly.

1. For this i used following code .

NSError *error;

NSData *jsonData = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://maps.googleapis.com/maps/api/directions/json?origin=chennai&destination=porur&sensor=false"]];

NSDictionary *jsonDict  = [NSJSONSerialization JSONObjectWithData:jsonData options:kNilOptions error:&error];

//NSLog(@"the json data is %@",jsonDict);


//--  json path --

NSString *polyString = [[[[ jsonDict objectForKey:@"routes"] objectAtIndex:0] objectForKey:@"overview_polyline"] objectForKey:@"points"];

NSString *TotalEstimatedTime = [[[[[[jsonDict objectForKey:@"routes"]objectAtIndex:0] objectForKey:@"legs"] objectAtIndex:0] objectForKey:@"duration"] objectForKey:@"text"];

NSLog(@" %@ ", polyString);
NSLog(@" %@ ", TotalEstimatedTime);


//===================== drawing path ===============================

NSMutableArray *decodepolyString = [self decodePolyLine:polyString];

GMSMutablePath *path = [GMSMutablePath path];

for (int i= 0; i< [decodepolyString count]; i++)
{
    CLLocation *location = [decodepolyString objectAtIndex:i];
    CLLocationCoordinate2D coordinate = location.coordinate;
    [path addCoordinate:coordinate];
}


GMSPolyline *overviewpolyline = [GMSPolyline polylineWithPath:path];

overviewpolyline.strokeColor = [UIColor blueColor];

overviewpolyline.strokeWidth = 4.f;
overviewpolyline.geodesic = YES;
overviewpolyline.map = self.GMSMapView1;

}

-(NSMutableArray *)decodePolyLine:(NSString *)encodedStr { NSMutableString *encoded = [[NSMutableString alloc] initWithCapacity:[encodedStr length]];

[encoded appendString:encodedStr];
[encoded replaceOccurrencesOfString:@"\\\\" withString:@"\\"
                            options:NSLiteralSearch
                              range:NSMakeRange(0, [encoded length])];
float len = [encoded length];
float index = 0;
NSMutableArray *array = [[NSMutableArray alloc] init];
float lat=0;
float lng=0;
while (index < len) {
    NSInteger b;
    NSInteger shift = 0;
    NSInteger result = 0;
    do {
        b = [encoded characterAtIndex:index++] - 63;
        result |= (b & 0x1f) << shift;
        shift += 5;
    } while (b >= 0x20);
    NSInteger dlat = ((result & 1) ? ~(result >> 1) : (result >> 1));
    lat += dlat;
    shift = 0;
    result = 0;
    do {
        b = [encoded characterAtIndex:index++] - 63;
        result |= (b & 0x1f) << shift;
        shift += 5;
    } while (b >= 0x20);
    NSInteger dlng = ((result & 1) ? ~(result >> 1) : (result >> 1));
    lng += dlng;
    NSNumber *latitude = [[NSNumber alloc] initWithFloat:lat * 1e-5];
    NSNumber *longitude = [[NSNumber alloc] initWithFloat:lng * 1e-5];

    CLLocation *location = [[CLLocation alloc] initWithLatitude:[latitude floatValue] longitude:[longitude floatValue]];
    [array addObject:location];
}

return array;

}

• please tell why it is happening and what is the solution for this ?
• and if you help me in iOS (objective c ) its good for me.