Calculate Nearest Site Latitude and Longitude

We have telecom Sites (Towers). Each Tower is identified by its Latitude and Longitude. We have Latitude and Longitude information in the database Site table. Suppose when we installed a new tower in a new location so how to find the nearest Site Latitude and Langitude from the New Site. Suppose conside the following method:

public void NearestSiteLatLong(double NewLocationLatitude, double NeLocationLongitude)

{

Fitch the stored Latitude and Langitude values from the database table Site and then compare each retrieved Latitude and Langitude from the database Table Site with the NewLocationLatitude and NewLocationLongitude and then find the nearest Latitude and Longitude

}

Here i am not sure how to compare i means which type of comparison is this?

Thanks in advance

private double distance(double lat1, double lon1, double lat2, double lon2, char unit) {
if ((lat1 == lat2) && (lon1 == lon2)) {
return 0;
}
else {
double theta = lon1 - lon2;
double dist = Math.Sin(deg2rad(lat1)) * Math.Sin(deg2rad(lat2)) + Math.Cos(deg2rad(lat1)) * Math.Cos(deg2rad(lat2)) * Math.Cos(deg2rad(theta));
dist = Math.Acos(dist);
dist = rad2deg(dist);
dist = dist * 60 * 1.1515;
if (unit == 'K') {
dist = dist * 1.609344;
} else if (unit == 'N') {
dist = dist * 0.8684;
}
return (dist);
}
}

You can also use GeoCordinate class of .NET

var sCoord = new GeoCoordinate(sLatitude, sLongitude);
var eCoord = new GeoCoordinate(eLatitude, eLongitude);
return sCoord.GetDistanceTo(eCoord);

You can use above sine formula to calucalte distance between two points (two lat,long) and then according to the distance you would know which of your site is the nearest one.