How to find the nearest 100 meters latitude and longitude depending upon the current location in objective c, Iphone

Question

How to find the nearest 100 meters latitude and longitude depending upon the current location, i have created a database in SQLITE3 which consists of set of latitudes and longitudes and corresponding there location name. Depending upon the current location i want to fetch the nearest 100 meters latitude and longitude in objective C, I am using the following code to get the Current location,

- (void)viewDidLoad {
    [super viewDidLoad];

    databaseName = @"searchdata.sql";

    NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentDir = [documentPaths objectAtIndex:0];
    databasePath = [documentDir stringByAppendingPathComponent:databaseName];

    [self checkAndCreateDatabase];
    [self readDataFromDatabase];
    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;

    locationManager = [[CLLocationManager alloc] init];
    locationManager.delegate = self;
    locationManager.distanceFilter = kCLDistanceFilterNone; // whenever we move
    locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters; // 100 m
    [locationManager startUpdatingLocation];

}

- (void)locationManager:(CLLocationManager *)manager
    didUpdateToLocation:(CLLocation *)newLocation
           fromLocation:(CLLocation *)oldLocation
{
    int degrees = newLocation.coordinate.latitude;
    double decimal = fabs(newLocation.coordinate.latitude - degrees);
    int minutes = decimal * 60;
    double seconds = decimal * 3600 - minutes * 60;
    NSString *lat = [NSString stringWithFormat:@"%d° %d' %1.4f\"", 
                     degrees, minutes, seconds];
    NSLog(@" Current Latitude : %@",lat);
    //latLabel.text = lat;
    degrees = newLocation.coordinate.longitude;
    decimal = fabs(newLocation.coordinate.longitude - degrees);
    minutes = decimal * 60;
    seconds = decimal * 3600 - minutes * 60;
    NSString *longt = [NSString stringWithFormat:@"%d° %d' %1.4f\"", 
                       degrees, minutes, seconds];
    NSLog(@" Current Longitude : %@",longt);
    //longLabel.text = longt;
}

so how to fetch or how to calculate the surrounding 100 meters latitudes and longitudes and display it.

Thanks for the help I am using the following formula

     -(double)kilometresBetweenPlace1:(CLLocationCoordinate2D) place1 andPlace2:(CLLocationCoordinate2D) place2 {

    double dlon = convertToRadians([pLong intValue] - [longt intValue]);
    double dlat = convertToRadians([pLat intValue] - [lat intValue]);

    double a = ( pow(sin(dlat / 2), 2) + cos(convertToRadians([lat intValue]))) * cos(convertToRadians([pLat intValue])) * pow(sin(dlon / 2), 2);
    double angle = 2 * asin(sqrt(a));
      return angle * RADIO;
}

and getting the following output 8505.369547 on return, i am just confused what is the value i am getting actually.

Answer 1

Perhaps the CoreLocation framework can help you with this issue? It seems the following method is made with your question in mind:

- (id)initCircularRegionWithCenter:(CLLocationCoordinate2D)center radius:(CLLocationDistance)radius identifier:(NSString *)identifier

You could test if a coordinate from your database falls within a region by using the following method:

- (BOOL)containsCoordinate:(CLLocationCoordinate2D)coordinate

I guess the above ain't ideal when your database contains a lot of locations. But perhaps one can filter out a set of locations to test based on some minimum and maximum latitude / longitude values.

---

Edit: as requested, an example (don't forget to import the CoreLocation framework):

- (void)startTest
{

#define COORDS_COUNT 4
#define RADIUS       10000.0f

    CLLocationCoordinate2D coords[COORDS_COUNT] = {
        CLLocationCoordinate2DMake(52.000004, 4.100002),
        CLLocationCoordinate2DMake(53.000009, 4.000003),
        CLLocationCoordinate2DMake(52.000001, 4.500008),
        CLLocationCoordinate2DMake(52.000002, 3.900900),
    };

    CLLocationCoordinate2D center = CLLocationCoordinate2DMake(52.0f, 4.0f); // Amsterdam
    CLRegion *region = [[CLRegion alloc] initCircularRegionWithCenter:center radius:RADIUS identifier:@"Amsterdam"];

    for (int i = 0; i < COORDS_COUNT; i++)
    {
        CLLocationCoordinate2D coord = coords[i];
        if ([region containsCoordinate:coord])
        {
            NSLog(@"location %f, %f is within %.0f meters of coord %f, %f", coord.latitude, coord.longitude, RADIUS, center.latitude, center.longitude);
        }
        else 
        {
            NSLog(@"location %f, %f is not within %.0f meters of coord %f, %f", coord.latitude, coord.longitude, RADIUS, center.latitude, center.longitude);        
        }
    }

}

---

Edit 2: I realize it's not exactly the answer you requested, but it seems to me this is what you need. As you can imagine the nearest 100 meters latitude / longitude near any coordinate consists of an virtually unlimited amount of coordinates in a circular region. My guess is you want to find objects within your database that are nearby some coordinate and the above code should help you achieve this. You can retrieve a set of results from your database and test if they are nearby some coordinate.

---

Edit 3: The following code is likely exactly what you need:

CLLocation *center = [[CLLocation alloc] initWithLatitude:52.0f longitude:4.0f]; // Amsterdam
CLLocation *location1 = [[CLLocation alloc] initWithLatitude:52.000004f longitude:4.100002f];

CLLocationDistance distance = [center distanceFromLocation:location1];
NSLog(@"%f", distance);    

---

Edit 4: with regards to your question about the custom object for your table view, use something like this:

@interface Location : NSObject 
@property (nonatomic, strong) NSString               *name;
@property (nonatomic, assign) CLLocationCoordinate2D  coordinate;
@end


@implementation Location
@synthesize name, coordinate;
@end