# How to convert latitude or longitude to meters?

###### Posted By: Adam Taylor

If I have a latitude or longitude reading in standard NMEA format is there an easy way / formula to convert that reading to meters, which I can then implement in Java (J9)?

Edit:

Ok seems what I want to do is not possible *easily*, however what I really want to do is:

Say I have a lat and long of a way point and a lat and long of a user is there an easy way to compare them to decide when to tell the user they are within a *reasonably* close distance of the way point? I realise reasonable is subject but is this easily do-able or still overly maths-y?

## Solution

Here is a javascript function:

```
function measure(lat1, lon1, lat2, lon2){ // generally used geo measurement function
var R = 6378.137; // Radius of earth in KM
var dLat = lat2 * Math.PI / 180 - lat1 * Math.PI / 180;
var dLon = lon2 * Math.PI / 180 - lon1 * Math.PI / 180;
var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(lat1 * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) *
Math.sin(dLon/2) * Math.sin(dLon/2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c;
return d * 1000; // meters
}
```

Explanation: https://en.wikipedia.org/wiki/Haversine_formula

The haversine formula determines the great-circle distance between two points on a sphere given their longitudes and latitudes.

###### Answered By: Anonymous

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