Objective-C for finding latitude and longitude range boundaries

GeoLocationUtils.m

//
//  GeoLocationUtils.m



#import "GeoLocationUtils.h"

@implementation GeoLocationUtils

float TO_RADIAN = 0.0174532925,
TO_DEGREE = 57.2957795,
TO_MILE = 0.621371192,
TO_KM = 1.609344;

float MIN_LAT, MAX_LAT, MIN_LON, MAX_LON;

+ (double) degreeToRadian: (double) degree {
    return degree * TO_RADIAN;
}

+ (double) radianToDegree: (double) radian {
    return radian * TO_DEGREE;
}

+ (float) kmToMile: (float) km {
    return km * TO_MILE;
}
+ (float) mileToKm: (float) mile {
    return mile * TO_KM;
}

+ (void) initializeLocal {
    MIN_LAT = [GeoLocationUtils degreeToRadian: -90.0];
    MAX_LAT = [GeoLocationUtils degreeToRadian: 90.0];
    MIN_LON = [GeoLocationUtils degreeToRadian: -180.0];
    MAX_LON = [GeoLocationUtils degreeToRadian: 180.0];
}

// Semi-axes of WGS-84 geoidal reference
float WGS84_a = 6378137.0; // Major semiaxis [meter]
float WGS84_b = 6356752.3; // Minor semiaxis [meter]

// Earth radius at a given latitude, according to the WGS-84 ellipsoid [m]
+ (float) WGS84EarthRadius: (float)lat {
    // http://en.wikipedia.org/wiki/Earth_radius
    
    float An = WGS84_a * WGS84_a * cos(lat);
    float Bn = WGS84_b * WGS84_b * sin(lat);
    float Ad = WGS84_a * cos(lat);
    float Bd = WGS84_b * sin(lat);
    return sqrt( (An * An + Bn * Bn) / (Ad * Ad + Bd * Bd) );
}


+(BOOL) checkBounds: (float) radLat RadianLong: (float) radLon  {
    if (radLat < MIN_LAT || radLat > MAX_LAT || radLon < MIN_LON || radLon > MAX_LON) {
        NSLog(@"radLat or radLon is out of bounds");
        return NO;
    }
    return YES;
}

+ (NSArray *) calculateBoundryForLatitude: (float)latitude Longitude: (float)longitude DistanceinKm: (float)distance {
    return [GeoLocationUtils calculateBoxBoundryForLatitude:[NSString stringWithFormat:@"%f", latitude] Longitude:[NSString stringWithFormat:@"%f",longitude] DistanceinKm: distance];
}


+ (NSArray *) calculateBoxBoundryForLatitude: (NSString *)latitude Longitude: (NSString *)longitude DistanceinKm: (float)distance {
    
    NSLog(@"Latitude - %@, Longitude - %@", latitude, longitude);
    
    [GeoLocationUtils initializeLocal];
    
    NSString *radLat = [NSString stringWithFormat:@"%f", [GeoLocationUtils degreeToRadian:[latitude doubleValue]]];
    NSString *radLon = [NSString stringWithFormat:@"%f", [GeoLocationUtils degreeToRadian:[longitude doubleValue]]];
    
//    NSLog(@"Radian Latitude - %@, Longitude - %@", radLat, radLon);
    
//    NSLog(@"Degree Latitude - %f, Longitude - %f", [GeoLocationUtils radianToDegree:[radLat floatValue]], [GeoLocationUtils radianToDegree: [radLon floatValue]]);

    if([GeoLocationUtils checkBounds: [radLat floatValue] RadianLong: [radLon floatValue]] == NO) {
        // Location Out of bounds
        return [[NSArray alloc] init];
    }

    NSDictionary *location = [[NSDictionary alloc] initWithObjectsAndKeys:latitude, kLatitude, longitude, kLongitude, radLat, kRadianLat, radLon, kRadianLong, nil];
    
    return [GeoLocationUtils boundingCoordinates:location distanceInKm:distance];
}

// Bounding box surrounding the point at given coordinates, assuming local approximation of Earth surface as a sphere of radius given by WGS84

+ (NSArray *) boundingCoordinates:(NSDictionary *)location  distanceInKm:(float)distance {
    if (distance < 0) {
        //        console.log("no location or distance");
        return [[NSArray alloc] init];
    }
    
    
//    NSLog(@"==== > Passed - %@", location);
    
    float lat = [[location objectForKey:kRadianLat] floatValue];
    float lon = [[location objectForKey:kRadianLong] floatValue];
//    NSLog(@"Passed Radian Latitude - %f, Longitude - %f", lat, lon);

    float halfSide = 1000 * distance;
    
    // Radius of Earth at given latitude
    float radius = [GeoLocationUtils WGS84EarthRadius: lat];
    
//    NSLog(@"Earth Radius in Meters - %f", radius);
    
    // Radius of the parallel at given latitude
    float pradius = radius * cos(lat);
    
    float latMin = lat - halfSide/radius;
    float latMax = lat + halfSide/radius;
    float lonMin = lon - halfSide/pradius;
    float lonMax = lon + halfSide/pradius;
    
    NSString *minLatStr = [NSString stringWithFormat: @"%f", [GeoLocationUtils radianToDegree: latMin]];
    NSString *maxLatStr = [NSString stringWithFormat: @"%f", [GeoLocationUtils radianToDegree: latMax]];
    
    NSString *minLonStr = [NSString stringWithFormat: @"%f", [GeoLocationUtils radianToDegree: lonMin]];
    NSString *maxLonStr = [NSString stringWithFormat: @"%f", [GeoLocationUtils radianToDegree: lonMax]];
    
    NSArray *boundries = [[NSArray alloc] initWithObjects: minLatStr, minLonStr, maxLatStr, maxLonStr, nil];
    NSLog(@"=====> Box Boundaries : %@", boundries);
    
    return boundries;
}

+ (float) getDistanceInKmForMinLat: (NSString *)minlat MinLong: (NSString *)minlong MaxLat: (NSString *)maxlat MaxLong: (NSString *)maxlong {
    
    float lat1 = [minlat floatValue];
    float lon1 = [minlong floatValue];
    float lat2 = [maxlat floatValue];
    float lon2 = [maxlong floatValue];
    
    float R = [GeoLocationUtils WGS84EarthRadius: lat1] / 1000; // Radius of the earth in km
    float dLat = [GeoLocationUtils degreeToRadian:(lat2 - lat1)];  // deg2rad below
    float dLon = [GeoLocationUtils degreeToRadian:(lon2-lon1)];
    
    float radLat1 = [GeoLocationUtils degreeToRadian: lat1];
    float radLat2 = [GeoLocationUtils degreeToRadian: lat2];
    
    float a = sin(dLat/2) * sin(dLat/2) + cos(radLat1) * cos(radLat2) * sin(dLon/2) * sin(dLon/2);
    float c = 2 * atan2(sqrt(a), sqrt(1-a));
    float d = R * c; // Distance in km
    return d;
}

@end