Calculating MAX and MIN Latitude and Longitude with distance from Location - Objective C

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挽巷
挽巷 2021-01-12 15:17

I need to compute MAX and MIN Latitude and Longitude values from a location with certain distance.

I have thousands of locations stored in CoreData, and I want to sh

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  •  醉梦人生
    2021-01-12 15:36

    Here's a possible solution:

    1. macros to convert Degrees to Radians

      #define deg2rad(degrees) ((degrees) / 180.0 M_PI)
      
    2. macros to hold my searching distance

      #define searchDistance 5.00 //float value in KM
      
    3. set the minimum and maximum Latitude, Longitude values

      float minLat = userLocation.coordinate.latitude - (searchDistance / 69);
      float maxLat = userLocation.coordinate.latitude + (searchDistance / 69);
      float minLon = userLocation.coordinate.latitude - searchDistance / fabs(cos(deg2rad(userLocation.coordinate.latitude))*69);
      float maxLon = userLocation.coordinate.longitude + searchDistance / fabs(cos(deg2rad(userLocation.coordinate.latitude))*69);
      
    4. create predicate as follows

      NSPredicate *predicate = [NSPredicate predicateWithFormat:@"latitude <= %f AND latitude >= %f AND longitude <= %f AND longitude >= %f", maxLat, minLat, maxLon, minLon];
      

    This will create a square around userLocation and check if a given location falls into its coordinates.

    Update: Swift 2.* implementation

    First create a function to compute degrees to radians

    func deg2rad(degrees:Double) -> Double{
        return degrees * M_PI / 180
    }
    

    Compute and create minimum and maximum Latitude and Longitude values

    let searchDistance:Double =  5.00 //float value in KM    
    
    let minLat = userLocation.coordinate.latitude - (searchDistance / 69)
    let maxLat = userLocation.coordinate.latitude + (searchDistance / 69)
    
    let minLon = userLocation.coordinate.longitude - searchDistance / fabs(cos(deg2rad(userLocation.coordinate.latitude))*69)
    let maxLon = userLocation.coordinate.longitude + searchDistance / fabs(cos(deg2rad(userLocation.coordinate.latitude))*69)
    

    Last create NSPredicate to query CoreData for locations. In my case I am querying for values latitude and longitude but you should change this to match your CoreData object

    let predicate = NSPredicate(format: "latitude <= \(maxLat) AND latitude >= \(minLat) AND longitude <= \(maxLon) AND longitude >= \(minLon)")
    

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