/// <summary>
/// Calculates the distance between two <see cref="GeoCoordinate"/> values. This method
/// uses the algorithm described at http://www.movable-type.co.uk/scripts/latlong.html.
/// </summary>
/// <param name="otherCoordinate">An instance of the <see cref="GeoCoordinate"/> class for comparison</param>
/// <returns>The distance between this <see cref="GeoCoordinate"/> instances and the provided instance</returns>
public double? GetDistanceTo(GeoCoordinate otherCoordinate)
{
if (otherCoordinate == null)
{
throw new ArgumentNullException("otherCoordinate");
}
// Ensure we have valid longitude and latitude values for the source
if (this.Latitude == null || this.Longitude == null)
{
return null;
}
// Ensure we have valid longitude and latitude values for the target
if (otherCoordinate.Latitude == null || otherCoordinate.Longitude == null)
{
return null;
}
const double radius = 6371; // Defines the radius of planet Earth. Often exposed simply as R.
// Caclculate the latitude and longitude changes
double deltaLat = (this.Latitude.ToDecimal().Value - otherCoordinate.Latitude.ToDecimal().Value).ToRad();
double deltaLng = (this.Longitude.ToDecimal().Value - otherCoordinate.Longitude.ToDecimal().Value).ToRad();
// Calculate the angle
double angle = Math.Sin(deltaLat / 2) * Math.Sin(deltaLat / 2) +
Math.Cos(this.Latitude.ToDecimal().Value.ToRad()) * Math.Cos(otherCoordinate.Latitude.ToDecimal().Value.ToRad()) *
Math.Sin(deltaLng / 2) * Math.Sin(deltaLng / 2);
// Calculate the circumference
double c = 2 * Math.Atan2(Math.Sqrt(angle), Math.Sqrt(1 - angle));
return radius * c;
}
/// <summary>
/// Attempts to parse a latitude and longitude string into a
/// new GeoCoordinate instance
/// </summary>
/// <param name="input">The longitude and latitude string</param>
/// <param name="output">A newly created GeoCoordinate instance</param>
/// <returns>true if the parsing was succesful; otherwsie false</returns>
public static bool TryParse(string input, out GeoCoordinate output)
{
// Validate input parameter
if (string.IsNullOrEmpty(input))
{
output = null;
return false;
}
// TODO: SUPPORT MGRS IN THE FUTURE
// The regex below parses Longitude and Latitude values and supports
// the following different formats:
// - 38° 47’ 44” N 077° 36’ 50” W
// - 38°47’44”N077°36’50”W
// - 38°47’44”N,077°36’50”W
// - 384744N 0773650W
// - 38°47’44”N 077°36’50”W
// - 38 47 44 N 77 36 50 W
// - 38 47 44.23 N 77 36 50.77 W
//const string longlatParseString = "^(?<lat_degrees>\\d{2})[°]?\\s*(?<lat_minutes>\\d{2})[’']?\\s*(?<lat_seconds>[\\d\\.]+)[”\\\"]?\\s*(?<lat_direction>[NnSs]{1})[\\s,_-]?(?<lng_degrees>\\d{2,3})[°]?\\s*(?<lng_minutes>\\d{2})[’']?\\s*(?<lng_seconds>[\\d\\.]+)[”\\\"]?\\s*(?<lng_direction>[EeWw]{1})$";
const string longlatParseString = @"^(?<lat_degrees>\d{2})[°]?\s*(?<lat_minutes>\d{2})[’']?\s*(?<lat_seconds>[\d\.]+)[”\""]?\s*(?<lat_direction>[NnSs]{1})[\s,_-]?(?<lng_degrees>\d{2,3})[°]?\s*(?<lng_minutes>\d{2})[’']?\s*(?<lng_seconds>[\d\.]+)[”\""]?\s*(?<lng_direction>[EeWw]{1})$";
Regex regex = new Regex(longlatParseString);
// Check if the regex matches the provided value
if (regex.IsMatch(input))
{
Match match = regex.Match(input);
//TODO: VALIDATE THE GROUPS
// Create a DMS instance for Latitude and Longitude
DMS latitude = new DMS(int.Parse(match.Groups["lat_degrees"].Value), int.Parse(match.Groups["lat_minutes"].Value), int.Parse(match.Groups["lat_seconds"].Value), (char)match.Groups["lat_direction"].Value[0]);
DMS longitude = new DMS(int.Parse(match.Groups["lng_degrees"].Value), int.Parse(match.Groups["lng_minutes"].Value), int.Parse(match.Groups["lng_seconds"].Value), (char)match.Groups["lng_direction"].Value[0]);
output = new GeoCoordinate(latitude, longitude);
return true;
}
// The regex does not match so the provided input cannot be parsed as a longitude and latitude
output = null;
return false;
}