In this tutorial, we will show you how to calculate the distance between two locations geolocated by using latitude and longitude in Ruby. This distance calculation uses the **Spherical Law of Cosines**, which uses trigonometry to measure the curvature of the earth, to accurately measure the distances on the Earth.

```
def distance(lat1, lon1, lat2, lon2, unit)
if (lat1 == lat2) && (lon1 == lon2)
return 0
else
theta = lon1 - lon2
dist = Math.sin(lat1 * Math::PI / 180) * Math.sin(lat2 * Math::PI / 180) + Math.cos(lat1 * Math::PI / 180) * Math.cos(lat2 * Math::PI / 180) * Math.cos(theta * Math::PI / 180)
dist = Math.acos(dist)
dist = dist * 180 / Math::PI
miles = dist * 60 * 1.1515
unit = unit.upcase
if unit == 'K'
return miles * 1.609344
elsif unit == 'N'
return miles * 0.8684
else
return miles
end
end
end
puts distance(32.9697, -96.80322, 29.46786, -98.53506, "M").to_s + " Miles";
puts distance(32.9697, -96.80322, 29.46786, -98.53506, "K").to_s + " Kilometers";
puts distance(32.9697, -96.80322, 29.46786, -98.53506, "N").to_s + " Nautical Miles";
```

The code above creates the function named **distance **to calculate the distance between two locations. It implies the simple spherical law of cosines that gives well-conditioned results down to distances as small as a few meters on the Earth’s surface. The distance function makes use of the spherical law of cosines formula `cos `

and derived into the distance calculation.*c* = cos *a* cos *b* + sin *a* sin *b* cos *C*

Parameters that are passed to the distance function are:**lat1**, **lon1** = Latitude and Longitude of point 1 in decimal degrees**lat2**, **lon2 **= Latitude and Longitude of point 2 in decimal degrees**unit **= the unit you desire for results where ‘M’ is the statute miles (default), ‘K’ is kilometers and ‘N’ is nautical miles