var pi = 3.14159265358979;
    var sm_a = 6378137.0;
    var sm_b = 6356752.314;
    var sm_EccSquared = 6.69437999013e-03;
    var UTMScaleFactor = 0.9996;
    function DegToRad (deg)
    {
        return (deg / 180.0 * pi)
    }
    function RadToDeg (rad)
    {
        return (rad / pi * 180.0)
    }
    function ArcLengthOfMeridian (phi)
    {
        var alpha, beta, gamma, delta, epsilon, n;
        var result;
        n = (sm_a - sm_b) / (sm_a + sm_b);
        alpha = ((sm_a + sm_b) / 2.0)
           * (1.0 + (Math.pow (n, 2.0) / 4.0) + (Math.pow (n, 4.0) / 64.0));
        beta = (-3.0 * n / 2.0) + (9.0 * Math.pow (n, 3.0) / 16.0)
           + (-3.0 * Math.pow (n, 5.0) / 32.0);
        gamma = (15.0 * Math.pow (n, 2.0) / 16.0)
            + (-15.0 * Math.pow (n, 4.0) / 32.0);
        delta = (-35.0 * Math.pow (n, 3.0) / 48.0)
            + (105.0 * Math.pow (n, 5.0) / 256.0);
        epsilon = (315.0 * Math.pow (n, 4.0) / 512.0);
    result = alpha
        * (phi + (beta * Math.sin (2.0 * phi))
            + (gamma * Math.sin (4.0 * phi))
            + (delta * Math.sin (6.0 * phi))
            + (epsilon * Math.sin (8.0 * phi)));

    return result;
    }
    function UTMCentralMeridian (zone)
    {
        var cmeridian;

        cmeridian = DegToRad (-183.0 + (zone * 6.0));
    
        return cmeridian;
    }
    function MapLatLonToXY (phi, lambda, lambda0, xy)
    {
        var N, nu2, ep2, t, t2, l;
        var l3coef, l4coef, l5coef, l6coef, l7coef, l8coef;
        var tmp;
        ep2 = (Math.pow (sm_a, 2.0) - Math.pow (sm_b, 2.0)) / Math.pow (sm_b, 2.0);
        nu2 = ep2 * Math.pow (Math.cos (phi), 2.0);
        N = Math.pow (sm_a, 2.0) / (sm_b * Math.sqrt (1 + nu2));
        t = Math.tan (phi);
        t2 = t * t;
        tmp = (t2 * t2 * t2) - Math.pow (t, 6.0);
        l = lambda - lambda0;
        l3coef = 1.0 - t2 + nu2;
    
        l4coef = 5.0 - t2 + 9 * nu2 + 4.0 * (nu2 * nu2);
    
        l5coef = 5.0 - 18.0 * t2 + (t2 * t2) + 14.0 * nu2
            - 58.0 * t2 * nu2;
    
        l6coef = 61.0 - 58.0 * t2 + (t2 * t2) + 270.0 * nu2
            - 330.0 * t2 * nu2;
    
        l7coef = 61.0 - 479.0 * t2 + 179.0 * (t2 * t2) - (t2 * t2 * t2);
    
        l8coef = 1385.0 - 3111.0 * t2 + 543.0 * (t2 * t2) - (t2 * t2 * t2);
        xy[0] = N * Math.cos (phi) * l
            + (N / 6.0 * Math.pow (Math.cos (phi), 3.0) * l3coef * Math.pow (l, 3.0))
            + (N / 120.0 * Math.pow (Math.cos (phi), 5.0) * l5coef * Math.pow (l, 5.0))
            + (N / 5040.0 * Math.pow (Math.cos (phi), 7.0) * l7coef * Math.pow (l, 7.0));
        xy[1] = ArcLengthOfMeridian (phi)
            + (t / 2.0 * N * Math.pow (Math.cos (phi), 2.0) * Math.pow (l, 2.0))
            + (t / 24.0 * N * Math.pow (Math.cos (phi), 4.0) * l4coef * Math.pow (l, 4.0))
            + (t / 720.0 * N * Math.pow (Math.cos (phi), 6.0) * l6coef * Math.pow (l, 6.0))
            + (t / 40320.0 * N * Math.pow (Math.cos (phi), 8.0) * l8coef * Math.pow (l, 8.0));
    
        return;
    }
    function LatLonToUTMXY (lat, lon, zone, xy)
    {
        MapLatLonToXY (lat, lon, UTMCentralMeridian (zone), xy);

        /* Adjust easting and northing for UTM system. */
        xy[0] = xy[0] * UTMScaleFactor + 500000.0;
        xy[1] = xy[1] * UTMScaleFactor;
        if (xy[1] < 0.0)
            xy[1] = xy[1] + 10000000.0;

        return zone;
    }
    function btnToUTM_OnClick ()
    {
        var xy = new Array(2);
        
        if (isNaN (parseFloat (document.frmConverter.XCoordinate2.value))) {
            alert ("Please enter a valid longitude in the lon field.");
            return false;
        }

        lon = parseFloat (document.frmConverter.XCoordinate2.value);

        if ((lon < -180.0) || (180.0 <= lon)) {
            alert ("The longitude you entered is out of range.  " +
                   "Please enter a number in the range [-180, 180).");
            return false;
        }

        if (isNaN (parseFloat (document.frmConverter.YCoordinate2.value))) {
            alert ("Please enter a valid latitude in the lat field.");
            return false;
        }

        lat = parseFloat (document.frmConverter.YCoordinate2.value);

        if ((lat < -90.0) || (90.0 < lat)) {
            alert ("The latitude you entered is out of range.  " +
                   "Please enter a number in the range [-90, 90].");
            return false;
        }
        zone = Math.floor ((lon + 180.0) / 6) + 1;
        zone = LatLonToUTMXY (DegToRad (lat), DegToRad (lon), zone, xy);
        document.frmConverter.txtX.value = xy[0];
        document.frmConverter.txtY.value = xy[1];
        document.frmConverter.txtZone.value = zone;
        return true;
    }