LKS-92 koordināšu pārrēķins uz platuma un garuma grādiem.

lks-92.php

<?php

// Ja šis nedod korektu rezultātu Y asī, atkomentē rindiņu, kur ir "$y -= -6000000.0;" 

function LKSToLatLon($x, $y)
{
    /* Ellipsoid model constants (actual values here are for WGS84) */
    $UTMScaleFactor = 0.9996;
    $sm_a = 6378137.0;
    $sm_b = 6356752.314;
    $x -= 500000.0;
    // Pirmā atšķirība no WGS84 - Kilometriņš šurpu, kilometriņš turpu.
    // Ja šis nedod korektu rezultāt, atkomentē sekojošo rindiņu. 
    // $y -= -6000000.0;
    $x /= $UTMScaleFactor;
    $y /= $UTMScaleFactor;
    // Otrā atšķirība no WGS84 - Centrālais meridiāns ir citur.
    $lambda0 = deg2rad(24);
    /* Precalculate n (Eq. 10.18) */
    $n = ($sm_a - $sm_b) / ($sm_a + $sm_b);
    /* Precalculate alpha_ (Eq. 10.22) */
    /* (Same as alpha in Eq. 10.17) */
    $alpha_ = (($sm_a + $sm_b) / 2.0)
        * (1 + (pow($n, 2.0) / 4) + (pow($n, 4.0) / 64));
    /* Precalculate y_ (Eq. 10.23) */
    $y_ = $y / $alpha_;
    /* Precalculate beta_ (Eq. 10.22) */
    $beta_ = (3.0 * $n / 2.0) + (-27.0 * pow($n, 3.0) / 32.0)
        + (269.0 * pow($n, 5.0) / 512.0);
    /* Precalculate gamma_ (Eq. 10.22) */
    $gamma_ = (21.0 * pow($n, 2.0) / 16.0)
        + (-55.0 * pow($n, 4.0) / 32.0);
    /* Precalculate delta_ (Eq. 10.22) */
    $delta_ = (151.0 * pow($n, 3.0) / 96.0)
        + (-417.0 * pow($n, 5.0) / 128.0);
    /* Precalculate epsilon_ (Eq. 10.22) */
    $epsilon_ = (1097.0 * pow($n, 4.0) / 512.0);
    /* Now calculate the sum of the series (Eq. 10.21) */
    $phif = $y_ + ($beta_ * sin(2.0 * $y_))
        + ($gamma_ * sin(4.0 * $y_))
        + ($delta_ * sin(6.0 * $y_))
        + ($epsilon_ * sin(8.0 * $y_));
    /*  Precalculate ep2 */
    $ep2 = (pow($sm_a, 2.0) - pow($sm_b, 2.0))
        / pow($sm_b, 2.0);
    /* Precalculate cos (phif) */
    $cf = cos($phif);
    /* Precalculate nuf2 */
    $nuf2 = $ep2 * pow($cf, 2.0);
    /* Precalculate Nf and initialize Nfpow */
    $Nf = pow($sm_a, 2.0) / ($sm_b * sqrt(1 + $nuf2));
    $Nfpow = $Nf;
    /* Precalculate tf */
    $tf = tan($phif);
    $tf2 = $tf * $tf;
    $tf4 = $tf2 * $tf2;
    /* Precalculate fractional coefficients for x**n in the equations
       below to simplify the expressions for latitude and longitude. */
    $x1frac = 1.0 / ($Nfpow * $cf);
    $Nfpow *= $Nf;   /* now equals Nf**2) */
    $x2frac = $tf / (2.0 * $Nfpow);
    $Nfpow *= $Nf;   /* now equals Nf**3) */
    $x3frac = 1.0 / (6.0 * $Nfpow * $cf);
    $Nfpow *= $Nf;   /* now equals Nf**4) */
    $x4frac = $tf / (24.0 * $Nfpow);
    $Nfpow *= $Nf;   /* now equals Nf**5) */
    $x5frac = 1.0 / (120.0 * $Nfpow * $cf);
    $Nfpow *= $Nf;   /* now equals Nf**6) */
    $x6frac = $tf / (720.0 * $Nfpow);
    $Nfpow *= $Nf;   /* now equals Nf**7) */
    $x7frac = 1.0 / (5040.0 * $Nfpow * $cf);
    $Nfpow *= $Nf;   /* now equals Nf**8) */
    $x8frac = $tf / (40320.0 * $Nfpow);
    /* Precalculate polynomial coefficients for x**n.
       -- x**1 does not have a polynomial coefficient. */
    $x2poly = -1.0 - $nuf2;
    $x3poly = -1.0 - 2 * $tf2 - $nuf2;
    $x4poly = 5.0 + 3.0 * $tf2 + 6.0 * $nuf2 - 6.0 * $tf2 * $nuf2
        - 3.0 * ($nuf2 * $nuf2) - 9.0 * $tf2 * ($nuf2 * $nuf2);
    $x5poly = 5.0 + 28.0 * $tf2 + 24.0 * $tf4 + 6.0 * $nuf2 + 8.0 * $tf2 * $nuf2;
    $x6poly = -61.0 - 90.0 * $tf2 - 45.0 * $tf4 - 107.0 * $nuf2
        + 162.0 * $tf2 * $nuf2;
    $x7poly = -61.0 - 662.0 * $tf2 - 1320.0 * $tf4 - 720.0 * ($tf4 * $tf2);
    $x8poly = 1385.0 + 3633.0 * $tf2 + 4095.0 * $tf4 + 1575 * ($tf4 * $tf2);
    /* Calculate latitude */
    $lat = $phif + $x2frac * $x2poly * ($x * $x)
        + $x4frac * $x4poly * pow($x, 4.0)
        + $x6frac * $x6poly * pow($x, 6.0)
        + $x8frac * $x8poly * pow($x, 8.0);
    /* Calculate longitude */
    $lon = $lambda0 + $x1frac * $x
        + $x3frac * $x3poly * pow($x, 3.0)
        + $x5frac * $x5poly * pow($x, 5.0)
        + $x7frac * $x7poly * pow($x, 7.0);
    return Array(rad2deg($lat), rad2deg($lon));
}

@soshial, yes, you can. As for URL scheme - I have no clue.