## Introduction

The simple code allows you to measure the distance between two places on earth with latitude and longitude pairs in meters.

## Background

Finding proximity between two points is important. In day to day life we speak about distances in Meters and KM. But mathematically how to convert the distance between two {latitude,longitude} pairs?

## Using the code

The logic is simple. Convert the values to radians. Than calculate d=sine(latitude distance)^2+cosine(longitude distance). distance=2* tan2(sqrt(d),sqrt(1-d)). Multiply the distance with earth radius to get geographical distance in radians. All you have to do is get it converted to meters.

public class DistanceInMeter
{
public static double distFrom(double lat1, double lng1, double lat2, double lng2) {
double earthRadius = 3958.75;
double dLat = toRadians(lat2-lat1);
double dLng = toRadians(lng2-lng1);
double a = Math.Sin(dLat/2) * Math.Sin(dLat/2) +
Math.Cos(Math.toRadians(lat1)) * Math.Cos(Math.toRadians(lat2)) *
Math.Sin(dLng/2) * Math.Sin(dLng/2);
double c = 2 * Math.Atan2(Math.sqrt(a), Math.sqrt(1-a));
double dist = earthRadius * c;
int meterConversion = 1609;
return (dist * meterConversion);
}
static double toRadians(double degree)
{
return (degree*0.0174532925 );
}
}

## Points of Interest

You can import Google map in you application and find all places within some distance. This function is typically helpful for spatial data mining.

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