ios - GoogleMap API Gives Wrong Coordinates for Direction between two Points

Question

I am using GoogleMap API for showing draw direction between two points on GoogleMap.

i want to give support on iOS 6.1 so i use GoogleMap i know about iOS7 recover this.

using below code for parsing and get Steps for coordinates to draw polyline on Map:

NSString *str=@"http://maps.googleapis.com/maps/api/directions/json?origin=bharuch,gujarat&destination=vadodara,gujarat&sensor=false";

NSURL *url=[[NSURL alloc]initWithString:[str stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];

NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];

NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
     NSError* error;

NSDictionary* json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];

NSArray* latestRoutes = [json objectForKey:@"routes"];

NSMutableDictionary *legs=[[[latestRoutes objectAtIndex:0] objectForKey:@"legs"] objectAtIndex:0];

NSArray *steps=[legs objectForKey:@"steps"];

NSString *startLocation,*endLocation,*totalDistance,*totalDuration;
     CLLocationCoordinate2D startLoc,endLoc;
     startLocation = [legs  objectForKey:@"start_address"];
     endLocation = [legs objectForKey:@"end_address"];
     totalDistance = [[legs objectForKey:@"distance"] objectForKey:@"text"];
     totalDuration = [[legs objectForKey:@"duration"] objectForKey:@"text"];
     startLoc=CLLocationCoordinate2DMake([[[legs objectForKey:@"start_location"] objectForKey:@"lat"] doubleValue], [[[legs objectForKey:@"start_location"] objectForKey:@"lng"] doubleValue]);
     endLoc=CLLocationCoordinate2DMake([[[legs objectForKey:@"end_location"] objectForKey:@"lat"] doubleValue], [[[legs objectForKey:@"end_location"] objectForKey:@"lng"] doubleValue]);

     NSMutableDictionary *tempDict;
     if ([steps count]!=0) {
         GMSMutablePath *path = [GMSMutablePath path];
         for(int idx = 0; idx < [steps count]+2; idx++){

            CLLocationCoordinate2D workingCoordinate;

            if (idx==0) {

                workingCoordinate=startLoc;

                [path addCoordinate:workingCoordinate];

            }
            else if (idx==[steps count]+1){

                workingCoordinate=endLoc;

                [path addCoordinate:workingCoordinate];
            }
            else{

                workingCoordinate=CLLocationCoordinate2DMake([[[[steps objectAtIndex:idx-1] objectForKey:@"start_location"] objectForKey:@"lat"] floatValue], [[[[steps objectAtIndex:idx-1] objectForKey:@"start_location"] objectForKey:@"lng"] floatValue]);

                [path addCoordinate:workingCoordinate];

            }
            tempDict = nil;
        }
        // create the polyline based on the array of points.

        GMSPolyline *rectangle = [GMSPolyline polylineWithPath:path];

        rectangle.strokeWidth=5.0;

        rectangle.map = mapView_;
    }

its gives only 24 steps means only 24 Coordinates for create point and draw Line on Map which is shown as below image:

you can see that line is not on proper road so what can i do to solve this? i also want to show direction on map too.

Answer 1

Below answer is for smooth path between two location with help of @A Báo:

-(void)viewDidLoad {

    // Create a GMSCameraPosition that tells the map to display the

    GMSCameraPosition *camera = [GMSCameraPosition cameraWithLatitude:21.718472 longitude:73.030422 zoom:6];
    mapView_ = [GMSMapView mapWithFrame:CGRectZero camera:camera];
    mapView_.delegate=self;
    mapView_.myLocationEnabled = YES;
    mapView_.settings.myLocationButton=YES;
    mapView_.settings.indoorPicker=NO;
    mapView_.settings.compassButton=YES;

    self.view = mapView_;

    NSString *str=@"http://maps.googleapis.com/maps/api/directions/json?origin=Bharuch,gujarat&destination=vadodara,gujarat&sensor=false";

    NSURL *url=[[NSURL alloc]initWithString:[str stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];

    NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];

    NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];

    NSError* error;
    NSDictionary* json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];

    NSArray* latestRoutes = [json objectForKey:@"routes"];

    NSString *points=[[[latestRoutes objectAtIndex:0] objectForKey:@"overview_polyline"] objectForKey:@"points"];

    @try {
        // TODO: better parsing. Regular expression?

        NSArray *temp= [self decodePolyLine:[points mutableCopy]];

        GMSMutablePath *path = [GMSMutablePath path];

        for(int idx = 0; idx < [temp count]; idx++)
        {
           CLLocation *location=[temp objectAtIndex:idx];

            [path addCoordinate:location.coordinate];

        }
        // create the polyline based on the array of points.

        GMSPolyline *rectangle = [GMSPolyline polylineWithPath:path];

        rectangle.strokeWidth=5.0;

        rectangle.map = mapView_;

    }
    @catch (NSException * e) {
        // TODO: show error
    }
}

-(NSMutableArray *)decodePolyLine: (NSMutableString *)encoded {
  [encoded replaceOccurrencesOfString:@"" withString:@""
                              options:NSLiteralSearch
                                range:NSMakeRange(0, [encoded length])];
  NSInteger len = [encoded length];
  NSInteger index = 0;
  NSMutableArray *array = [[NSMutableArray alloc] init] ;
  NSInteger lat=0;
  NSInteger 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] ;
      printf("[%f,", [latitude doubleValue]);
      printf("%f]", [longitude doubleValue]);
      CLLocation *loc = [[CLLocation alloc] initWithLatitude:[latitude floatValue] longitude:[longitude floatValue]] ;
      [array addObject:loc];
  }

  return array;
}

Screenshot of this code you can compare it with previous screenshot which i used in asking Question: