latitude and longitude bounding box for C#?

Question

I just want to find a straightforward, C# class that takes in a starting latitude and longitude and a distance and finds the bounding box (max lat, min lat, max lon, min lon

Answer 1

I know I'm resurrecting a two year old question, but in the event that anyone gets here from Google, I've written a C# class library that does exactly this and a little more. I've created a Github repository to host the code and will be writing a blog post covering it shortly.

Geolocation repository

Answer 2

If you only have a starting latitude, longitude and altitude then there is no bounding box as you have only defined a single point in space. Any rectangle/bounding box would require at least two points to define it!

Answer 3

Here's what you are asking for. Kudos to Federico A. Ramponi who wrote the original in Python here.

public class MapPoint
{
    public double Longitude { get; set; } // In Degrees
    public double Latitude { get; set; } // In Degrees
}

public class BoundingBox
{
    public MapPoint MinPoint { get; set; }
    public MapPoint MaxPoint { get; set; }
}        

// Semi-axes of WGS-84 geoidal reference
private const double WGS84_a = 6378137.0; // Major semiaxis [m]
private const double WGS84_b = 6356752.3; // Minor semiaxis [m]

// 'halfSideInKm' is the half length of the bounding box you want in kilometers.
public static BoundingBox GetBoundingBox(MapPoint point, double halfSideInKm)
{            
    // Bounding box surrounding the point at given coordinates,
    // assuming local approximation of Earth surface as a sphere
    // of radius given by WGS84
    var lat = Deg2rad(point.Latitude);
    var lon = Deg2rad(point.Longitude);
    var halfSide = 1000 * halfSideInKm;

    // Radius of Earth at given latitude
    var radius = WGS84EarthRadius(lat);
    // Radius of the parallel at given latitude
    var pradius = radius * Math.Cos(lat);

    var latMin = lat - halfSide / radius;
    var latMax = lat + halfSide / radius;
    var lonMin = lon - halfSide / pradius;
    var lonMax = lon + halfSide / pradius;

    return new BoundingBox { 
        MinPoint = new MapPoint { Latitude = Rad2deg(latMin), Longitude = Rad2deg(lonMin) },
        MaxPoint = new MapPoint { Latitude = Rad2deg(latMax), Longitude = Rad2deg(lonMax) }
    };            
}

// degrees to radians
private static double Deg2rad(double degrees)
{
    return Math.PI * degrees / 180.0;
}

// radians to degrees
private static double Rad2deg(double radians)
{
    return 180.0 * radians / Math.PI;
}

// Earth radius at a given latitude, according to the WGS-84 ellipsoid [m]
private static double WGS84EarthRadius(double lat)
{
    // http://en.wikipedia.org/wiki/Earth_radius
    var An = WGS84_a * WGS84_a * Math.Cos(lat);
    var Bn = WGS84_b * WGS84_b * Math.Sin(lat);
    var Ad = WGS84_a * Math.Cos(lat);
    var Bd = WGS84_b * Math.Sin(lat);
    return Math.Sqrt((An*An + Bn*Bn) / (Ad*Ad + Bd*Bd));
}