How to return points within lightning?

Question

I am developing an app where I would need to return points (Lat, Long) in a radius of size X (Km) from the user’s location (Lat, Long). I’ve devised the following logic:

• Get current user location

• Insert the user’s location as the point A of the radius, and the distance of that radius as the point B, in latitude and longitude.

  But I’m having a hard time determining how to calculate and convert that distance to meters or kilometers.

  The points that will be searched are stored in the app, not requiring requests from a web service.

  At the end I will list in an array the points that are within the radius.

  Does anyone know an API or methods that can help you craft this function.

  NOTE: I am using the API google maps iOS to show the map, I am storing the points of the places that will be searched within the radius in the App itself. I’m using Google Maps coordinates.

Image to illustrate:

Answer 1

If your problem is to determine if a pair of coordinates belongs to a circular region then I suggest using the following code, assuming a radius of 1km:

CLLocation *posicaoAtual = <Posicao retornada pelo CoreLocation>;

CLCircularRegion *areaCircular  = [[CLCircularRegion alloc] initWithCenter:posicaoAtual.coordinate radius:1000 identifier:@"MyID"];

CLLocation *outraPosicao = <Posicao que você quer testar se está dentro da região>;
if (areaCircular containsCoordinate:outraPosicao.coordinate])
    NSLog("Está dentro da região");

Answer 2

I did this in a project where I used the distance between two points ma taking into account the curvature of the earth, at small distances I see no problem, but at larger distances this error is gradually greater.

 public double distaincia(double latInicial, double latFinal, double lngInicial, double lngFinal) {
    double distancia = 6378140 * Math.acos(Math.cos(Math.PI * (90 - latFinal) / 180) * Math.cos((90 - latInicial) * Math.PI / 180)
            + Math.sin((90 - latFinal) * Math.PI / 180) * Math.sin((90 - latInicial) * Math.PI / 180) * Math.cos((lngInicial - lngFinal) * Math.PI / 180));
    return distancia;
}

this returns me the distance between two points in meters, so if you define a radius of 30KM is just to check this distance.

Answer 3

What you can do is, instead of finding the dots within a circle, find the dots within a frame that has that circle inscribed.
A frame whose side is equal to twice the radius being in its center the user’s location.

The Googlemaps api for android has a class with several methods that allow to make some calculations with points defined as Lat/Long allowing to calculate, namely, another point at a certain distance from the first second a direction.

I think this class does not exist in the API google maps iOS but found in Github an alternative.

The solution I suggest is to calculate the points that are left from the user’s location at a distance thunderbolt in directions (A)0º, (B)90º, (C)180º and (D)270º
For this use the function computeOffsetWithLatitude

The points(P) inside the square will be those whose Lat/Long make the following expression true:

P.Lat <= A.Lat && P.Lat >= C.Lat && P.Long <= B.Lon && P.Long >= D.Long