Autoit GPS distance calculation

Global $fLocation1[2], $fLocation2[2]

;~      Location 1
$fLocation1[0] = 52.918862
$fLocation1[1] = -1.474920

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;~      Location 2
$fLocation2[0] = 53.519629
$fLocation2[1] = -1.129435

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$fDistance = Distance($fLocation1[0], $fLocation1[1], $fLocation2[0], $fLocation2[1])

MsgBox(0,0, $fDistance)


Func Distance($_Lat1, $_Lon1, $_Lat2, $_Lon2) ; I translated this from a javascript recommendation.
    Local $RadiusOfEarth = 6371.008 ;6371 is the volumetric mean average radius of earth.

    Local $_dLat = Deg2Rad($_Lat2 - $_Lat1) ; No clue...
    Local $_dLon = Deg2Rad($_Lon2 - $_Lon1) ; No clue...

    Local $_a = (Sin($_dLat / 2) * Sin($_dLat / 2)) + (Cos(Deg2Rad($_Lat1)) * Cos(Deg2Rad($_Lat2))) * _ ; No clue...
            (Sin($_dLon / 2) * Sin($_dLon / 2)) ; No clue...

    Local $_C = 2 * ATan2(Sqrt($_a), Sqrt(1 - $_a)) ; No clue...

    Local $_d = $RadiusOfEarth * $_C ; No clue...

    Return Round(($_d * 1000) * 0.000621371192237, 3) ; I added this to convert meters to miles and returns this figure to the caller, rounded to 3 decimal places.
EndFunc   ;==>Distance

Func Deg2Rad($_input) ; I translated this from a javascript recommendation (There was no such function in AutoIt, so I had to search for one)
    Local $Pi = 3.1415926535897932384626433832795
    Return $_input * $Pi / 180
EndFunc   ;==>Deg2Rad


Func ATan2($y, $x) ; Taken from the AutoIt forum, where someone else needed the ATan2 function. This was the best, fastest option of the two provided.
    Return (2 * ATan($y / ($x + Sqrt($x * $x + $y * $y))))
EndFunc   ;==>ATan2