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<?php
//--------------------------------------------------------------------------
// PHPcoord
// phpcoord.php
//
// (c) 2005 Jonathan Stott
//
// Created on 11-Aug-2005
//
// 2.3 - 24 Aug 2006
// - Changed OSRef->toSixFigureString() so that the eastings and northings
// are rounded rather than floored.
// 2.2 - 11 Feb 2006
// - Used different algorithm for calculating distance between latitudes
// and longitudes - fixes a number of problems with distance calculations
// 2.1 - 22 Dec 2005
// - Added getOSRefFromSixFigureReference function
// 2.0 - 21 Dec 2005
// - Completely different object design - conversion functions now through
// objects rather than static functions
// - Updated comments and documentation
// 1.1 - 11 Sep 2005
// - Added OSGB36/WGS84 data conversions
// 1.0 - 11 Aug 2005
// - Initial version
//--------------------------------------------------------------------------
// ================================================================== LatLng
class LatLng {
var $lat;
var $lng;
/**
* Create a new LatLng object from the given latitude and longitude
*
* @param lat latitude
* @param lng longitude
*/
function LatLng($lat, $lng) {
$this->lat = $lat;
$this->lng = $lng;
}
/**
* Return a string representation of this LatLng object
*
* @return a string representation of this LatLng object
*/
function toString() {
return "(" . $this->lat . ", " . $this->lng . ")";
}
/**
* Calculate the surface distance between this LatLng object and the one
* passed in as a parameter.
*
* @param to a LatLng object to measure the surface distance to
* @return the surface distance
*/
function distance($to) {
$er = 6366.707;
$latFrom = deg2rad($this->lat);
$latTo = deg2rad($to->lat);
$lngFrom = deg2rad($this->lng);
$lngTo = deg2rad($to->lng);
$x1 = $er * cos($lngFrom) * sin($latFrom);
$y1 = $er * sin($lngFrom) * sin($latFrom);
$z1 = $er * cos($latFrom);
$x2 = $er * cos($lngTo) * sin($latTo);
$y2 = $er * sin($lngTo) * sin($latTo);
$z2 = $er * cos($latTo);
$d = acos(sin($latFrom)*sin($latTo) + cos($latFrom)*cos($latTo)*cos($lngTo-$lngFrom)) * $er;
return $d;
}
/**
* Convert this LatLng object from OSGB36 datum to WGS84 datum.
*/
function OSGB36ToWGS84() {
$airy1830 = new RefEll(6377563.396, 6356256.909);
$a = $airy1830->maj;
$b = $airy1830->min;
$eSquared = $airy1830->ecc;
$phi = deg2rad($this->lat);
$lambda = deg2rad($this->lng);
$v = $a / (sqrt(1 - $eSquared * sinSquared($phi)));
$H = 0; // height
$x = ($v + $H) * cos($phi) * cos($lambda);
$y = ($v + $H) * cos($phi) * sin($lambda);
$z = ((1 - $eSquared) * $v + $H) * sin($phi);
$tx = 446.448;
$ty = -124.157;
$tz = 542.060;
$s = -0.0000204894;
$rx = deg2rad( 0.00004172222);
$ry = deg2rad( 0.00006861111);
$rz = deg2rad( 0.00023391666);
$xB = $tx + ($x * (1 + $s)) + (-$rx * $y) + ($ry * $z);
$yB = $ty + ($rz * $x) + ($y * (1 + $s)) + (-$rx * $z);
$zB = $tz + (-$ry * $x) + ($rx * $y) + ($z * (1 + $s));
$wgs84 = new RefEll(6378137.000, 6356752.3141);
$a = $wgs84->maj;
$b = $wgs84->min;
$eSquared = $wgs84->ecc;
$lambdaB = rad2deg(atan($yB / $xB));
$p = sqrt(($xB * $xB) + ($yB * $yB));
$phiN = atan($zB / ($p * (1 - $eSquared)));
for ($i = 1; $i < 10; $i++) {
$v = $a / (sqrt(1 - $eSquared * sinSquared($phiN)));
$phiN1 = atan(($zB + ($eSquared * $v * sin($phiN))) / $p);
$phiN = $phiN1;
}
$phiB = rad2deg($phiN);
$this->lat = $phiB;
$this->lng = $lambdaB;
}
/**
* Convert this LatLng object from WGS84 datum to OSGB36 datum.
*/
function WGS84ToOSGB36() {
$wgs84 = new RefEll(6378137.000, 6356752.3141);
$a = $wgs84->maj;
$b = $wgs84->min;
$eSquared = $wgs84->ecc;
$phi = deg2rad($this->lat);
$lambda = deg2rad($this->lng);
$v = $a / (sqrt(1 - $eSquared * sinSquared($phi)));
$H = 0; // height
$x = ($v + $H) * cos($phi) * cos($lambda);
$y = ($v + $H) * cos($phi) * sin($lambda);
$z = ((1 - $eSquared) * $v + $H) * sin($phi);
$tx = -446.448;
$ty = 124.157;
$tz = -542.060;
$s = 0.0000204894;
$rx = deg2rad(-0.00004172222);
$ry = deg2rad(-0.00006861111);
$rz = deg2rad(-0.00023391666);
$xB = $tx + ($x * (1 + $s)) + (-$rx * $y) + ($ry * $z);
$yB = $ty + ($rz * $x) + ($y * (1 + $s)) + (-$rx * $z);
$zB = $tz + (-$ry * $x) + ($rx * $y) + ($z * (1 + $s));
$airy1830 = new RefEll(6377563.396, 6356256.909);
$a = $airy1830->maj;
$b = $airy1830->min;
$eSquared = $airy1830->ecc;
$lambdaB = rad2deg(atan($yB / $xB));
$p = sqrt(($xB * $xB) + ($yB * $yB));
$phiN = atan($zB / ($p * (1 - $eSquared)));
for ($i = 1; $i < 10; $i++) {
$v = $a / (sqrt(1 - $eSquared * sinSquared($phiN)));
$phiN1 = atan(($zB + ($eSquared * $v * sin($phiN))) / $p);
$phiN = $phiN1;
}
$phiB = rad2deg($phiN);
$this->lat = $phiB;
$this->lng = $lambdaB;
}
/**
* Convert this LatLng object into an OSGB grid reference. Note that this
* function does not take into account the bounds of the OSGB grid -
* beyond the bounds of the OSGB grid, the resulting OSRef object has no
* meaning
*
* @return the converted OSGB grid reference
*/
function toOSRef() {
$airy1830 = new RefEll(6377563.396, 6356256.909);
$OSGB_F0 = 0.9996012717;
$N0 = -100000.0;
$E0 = 400000.0;
$phi0 = deg2rad(49.0);
$lambda0 = deg2rad(-2.0);
$a = $airy1830->maj;
$b = $airy1830->min;
$eSquared = $airy1830->ecc;
$phi = deg2rad($this->lat);
$lambda = deg2rad($this->lng);
$E = 0.0;
$N = 0.0;
$n = ($a - $b) / ($a + $b);
$v = $a * $OSGB_F0 * pow(1.0 - $eSquared * sinSquared($phi), -0.5);
$rho =
$a * $OSGB_F0 * (1.0 - $eSquared) * pow(1.0 - $eSquared * sinSquared($phi), -1.5);
$etaSquared = ($v / $rho) - 1.0;
$M =
($b * $OSGB_F0)
* (((1 + $n + ((5.0 / 4.0) * $n * $n) + ((5.0 / 4.0) * $n * $n * $n))
* ($phi - $phi0))
- (((3 * $n) + (3 * $n * $n) + ((21.0 / 8.0) * $n * $n * $n))
* sin($phi - $phi0)
* cos($phi + $phi0))
+ ((((15.0 / 8.0) * $n * $n) + ((15.0 / 8.0) * $n * $n * $n))
* sin(2.0 * ($phi - $phi0))
* cos(2.0 * ($phi + $phi0)))
- (((35.0 / 24.0) * $n * $n * $n)
* sin(3.0 * ($phi - $phi0))
* cos(3.0 * ($phi + $phi0))));
$I = $M + $N0;
$II = ($v / 2.0) * sin($phi) * cos($phi);
$III =
($v / 24.0)
* sin($phi)
* pow(cos($phi), 3.0)
* (5.0 - tanSquared($phi) + (9.0 * $etaSquared));
$IIIA =
($v / 720.0)
* sin($phi)
* pow(cos($phi), 5.0)
* (61.0 - (58.0 * tanSquared($phi)) + pow(tan($phi), 4.0));
$IV = $v * cos($phi);
$V = ($v / 6.0) * pow(cos($phi), 3.0) * (($v / $rho) - tanSquared($phi));
$VI =
($v / 120.0)
* pow(cos($phi), 5.0)
* (5.0
- (18.0 * tanSquared($phi))
+ (pow(tan($phi), 4.0))
+ (14 * $etaSquared)
- (58 * tanSquared($phi) * $etaSquared));
$N =
$I
+ ($II * pow($lambda - $lambda0, 2.0))
+ ($III * pow($lambda - $lambda0, 4.0))
+ ($IIIA * pow($lambda - $lambda0, 6.0));
$E =
$E0
+ ($IV * ($lambda - $lambda0))
+ ($V * pow($lambda - $lambda0, 3.0))
+ ($VI * pow($lambda - $lambda0, 5.0));
return new OSRef($E, $N);
}
/**
* Convert a latitude and longitude to an UTM reference
*
* @return the converted UTM reference
*/
function toUTMRef() {
$wgs84 = new RefEll(6378137, 6356752.314);
$UTM_F0 = 0.9996;
$a = $wgs84->maj;
$eSquared = $wgs84->ecc;
$longitude = $this->lng;
$latitude = $this->lat;
$latitudeRad = $latitude * (pi() / 180.0);
$longitudeRad = $longitude * (pi() / 180.0);
$longitudeZone = (int) (($longitude + 180.0) / 6.0) + 1;
// Special zone for Norway
if ($latitude >= 56.0
&& $latitude < 64.0
&& $longitude >= 3.0
&& $longitude < 12.0) {
$longitudeZone = 32;
}
// Special zones for Svalbard
if ($latitude >= 72.0 && $latitude < 84.0) {
if ($longitude >= 0.0 && $longitude < 9.0) {
$longitudeZone = 31;
} else if ($longitude >= 9.0 && $longitude < 21.0) {
$longitudeZone = 33;
} else if ($longitude >= 21.0 && $longitude < 33.0) {
$longitudeZone = 35;
} else if ($longitude >= 33.0 && $longitude < 42.0) {
$longitudeZone = 37;
}
}
$longitudeOrigin = ($longitudeZone - 1) * 6 - 180 + 3;
$longitudeOriginRad = $longitudeOrigin * (pi() / 180.0);
$UTMZone = getUTMLatitudeZoneLetter($latitude);
$ePrimeSquared = ($eSquared) / (1 - $eSquared);
$n = $a / sqrt(1 - $eSquared * sin($latitudeRad) * sin($latitudeRad));
$t = tan($latitudeRad) * tan($latitudeRad);
$c = $ePrimeSquared * cos($latitudeRad) * cos($latitudeRad);
$A = cos($latitudeRad) * ($longitudeRad - $longitudeOriginRad);
$M =
$a
* ((1
- $eSquared / 4
- 3 * $eSquared * $eSquared / 64
- 5 * $eSquared * $eSquared * $eSquared / 256)
* $latitudeRad
- (3 * $eSquared / 8
+ 3 * $eSquared * $eSquared / 32
+ 45 * $eSquared * $eSquared * $eSquared / 1024)
* sin(2 * $latitudeRad)
+ (15 * $eSquared * $eSquared / 256
+ 45 * $eSquared * $eSquared * $eSquared / 1024)
* sin(4 * $latitudeRad)
- (35 * $eSquared * $eSquared * $eSquared / 3072)
* sin(6 * $latitudeRad));
$UTMEasting =
(double) ($UTM_F0
* $n
* ($A
+ (1 - $t + $c) * pow($A, 3.0) / 6
+ (5 - 18 * $t + $t * $t + 72 * $c - 58 * $ePrimeSquared)
* pow($A, 5.0)
/ 120)
+ 500000.0);
$UTMNorthing =
(double) ($UTM_F0
* ($M
+ $n
* tan($latitudeRad)
* ($A * $A / 2
+ (5 - $t + (9 * $c) + (4 * $c * $c)) * pow($A, 4.0) / 24
+ (61 - (58 * $t) + ($t * $t) + (600 * $c) - (330 * $ePrimeSquared))
* pow($A, 6.0)
/ 720)));
// Adjust for the southern hemisphere
if ($latitude < 0) {
$UTMNorthing += 10000000.0;
}
return new UTMRef($UTMEasting, $UTMNorthing, $UTMZone, $longitudeZone);
}
}
// =================================================================== OSRef
// References given with OSRef are accurate to 1m.
class OSRef {
var $easting;
var $northing;
/**
* Create a new OSRef object representing an OSGB grid reference. Note
* that the parameters for this constructor require eastings and
* northings with 1m accuracy and need to be absolute with respect to
* the whole of the British Grid. For example, to create an OSRef
* object from the six-figure grid reference TG514131, the easting would
* be 651400 and the northing would be 313100.
*
* Grid references with accuracy greater than 1m can be represented
* using floating point values for the easting and northing. For example,
* a value representing an easting or northing accurate to 1mm would be
* given as 651400.0001.
*
* @param easting the easting of the reference (with 1m accuracy)
* @param northing the northing of the reference (with 1m accuracy)
*/
function OSRef($easting, $northing) {
$this->easting = $easting;
$this->northing = $northing;
}
/**
* Convert this grid reference into a string showing the exact values
* of the easting and northing.
*
* @return
*/
function toString() {
return "(" . $this->easting . ", " . $this->northing . ")";
}
function toSplitString() {
$result['easting'] = $this->easting;
$result['northing'] = $this->northing;
return $result;
}
/**
* Convert this grid reference into a string using a standard six-figure
* grid reference including the two-character designation for the 100km
* square. e.g. TG514131.
*
* @return
*/
function toSixFigureString() {
$hundredkmE = floor($this->easting / 100000);
$hundredkmN = floor($this->northing / 100000);
$firstLetter = "";
if ($hundredkmN < 5) {
if ($hundredkmE < 5) {
$firstLetter = "S";
} else {
$firstLetter = "T";
}
} else if ($hundredkmN < 10) {
if ($hundredkmE < 5) {
$firstLetter = "N";
} else {
$firstLetter = "O";
}
} else {
$firstLetter = "H";
}
$secondLetter = "";
$index = 65 + ((4 - ($hundredkmN % 5)) * 5) + ($hundredkmE % 5);
$ti = $index;
if ($index >= 73) $index++;
$secondLetter = chr($index);
$e = round(($this->easting - (100000 * $hundredkmE)) / 100);
$n = round(($this->northing - (100000 * $hundredkmN)) / 100);
return sprintf("%s%s%03d%03d", $firstLetter, $secondLetter, $e, $n);
}
/**
* Convert this grid reference into a latitude and longitude
*
* @return
*/
function toLatLng() {
$airy1830 = new RefEll(6377563.396, 6356256.909);
$OSGB_F0 = 0.9996012717;
$N0 = -100000.0;
$E0 = 400000.0;
$phi0 = deg2rad(49.0);
$lambda0 = deg2rad(-2.0);
$a = $airy1830->maj;
$b = $airy1830->min;
$eSquared = $airy1830->ecc;
$phi = 0.0;
$lambda = 0.0;
$E = $this->easting;
$N = $this->northing;
$n = ($a - $b) / ($a + $b);
$M = 0.0;
$phiPrime = (($N - $N0) / ($a * $OSGB_F0)) + $phi0;
do {
$M =
($b * $OSGB_F0)
* (((1 + $n + ((5.0 / 4.0) * $n * $n) + ((5.0 / 4.0) * $n * $n * $n))
* ($phiPrime - $phi0))
- (((3 * $n) + (3 * $n * $n) + ((21.0 / 8.0) * $n * $n * $n))
* sin($phiPrime - $phi0)
* cos($phiPrime + $phi0))
+ ((((15.0 / 8.0) * $n * $n) + ((15.0 / 8.0) * $n * $n * $n))
* sin(2.0 * ($phiPrime - $phi0))
* cos(2.0 * ($phiPrime + $phi0)))
- (((35.0 / 24.0) * $n * $n * $n)
* sin(3.0 * ($phiPrime - $phi0))
* cos(3.0 * ($phiPrime + $phi0))));
$phiPrime += ($N - $N0 - $M) / ($a * $OSGB_F0);
} while (($N - $N0 - $M) >= 0.001);
$v = $a * $OSGB_F0 * pow(1.0 - $eSquared * sinSquared($phiPrime), -0.5);
$rho =
$a
* $OSGB_F0
* (1.0 - $eSquared)
* pow(1.0 - $eSquared * sinSquared($phiPrime), -1.5);
$etaSquared = ($v / $rho) - 1.0;
$VII = tan($phiPrime) / (2 * $rho * $v);
$VIII =
(tan($phiPrime) / (24.0 * $rho * pow($v, 3.0)))
* (5.0
+ (3.0 * tanSquared($phiPrime))
+ $etaSquared
- (9.0 * tanSquared($phiPrime) * $etaSquared));
$IX =
(tan($phiPrime) / (720.0 * $rho * pow($v, 5.0)))
* (61.0
+ (90.0 * tanSquared($phiPrime))
+ (45.0 * tanSquared($phiPrime) * tanSquared($phiPrime)));
$X = sec($phiPrime) / $v;
$XI =
(sec($phiPrime) / (6.0 * $v * $v * $v))
* (($v / $rho) + (2 * tanSquared($phiPrime)));
$XII =
(sec($phiPrime) / (120.0 * pow($v, 5.0)))
* (5.0
+ (28.0 * tanSquared($phiPrime))
+ (24.0 * tanSquared($phiPrime) * tanSquared($phiPrime)));
$XIIA =
(sec($phiPrime) / (5040.0 * pow($v, 7.0)))
* (61.0
+ (662.0 * tanSquared($phiPrime))
+ (1320.0 * tanSquared($phiPrime) * tanSquared($phiPrime))
+ (720.0
* tanSquared($phiPrime)
* tanSquared($phiPrime)
* tanSquared($phiPrime)));
$phi =
$phiPrime
- ($VII * pow($E - $E0, 2.0))
+ ($VIII * pow($E - $E0, 4.0))
- ($IX * pow($E - $E0, 6.0));
$lambda =
$lambda0
+ ($X * ($E - $E0))
- ($XI * pow($E - $E0, 3.0))
+ ($XII * pow($E - $E0, 5.0))
- ($XIIA * pow($E - $E0, 7.0));
return new LatLng(rad2deg($phi), rad2deg($lambda));
}
}
// ================================================================== UTMRef
class UTMRef {
var $easting;
var $northing;
var $latZone;
var $lngZone;
/**
* Create a new object representing a UTM reference.
*
* @param easting
* @param northing
* @param latZone
* @param lngZone
*/
function UTMRef($easting, $northing, $latZone, $lngZone) {
$this->easting = $easting;
$this->northing = $northing;
$this->latZone = $latZone;
$this->lngZone = $lngZone;
}
/**
* Return a string representation of this UTM reference
*
* @return
*/
function toString() {
return $this->lngZone . $this->latZone . " " .
$this->easting . " " . $this->northing;
}
/**
* Convert this UTM reference to a latitude and longitude
*
* @return the converted latitude and longitude
*/
function toLatLng() {
$wgs84 = new RefEll(6378137, 6356752.314);
$UTM_F0 = 0.9996;
$a = $wgs84->maj;
$eSquared = $wgs84->ecc;
$ePrimeSquared = $eSquared / (1.0 - $eSquared);
$e1 = (1 - sqrt(1 - $eSquared)) / (1 + sqrt(1 - $eSquared));
$x = $this->easting - 500000.0;;
$y = $this->northing;
$zoneNumber = $this->lngZone;
$zoneLetter = $this->latZone;
$longitudeOrigin = ($zoneNumber - 1.0) * 6.0 - 180.0 + 3.0;
// Correct y for southern hemisphere
if ((ord($zoneLetter) - ord("N")) < 0) {
$y -= 10000000.0;
}
$m = $y / $UTM_F0;
$mu =
$m
/ ($a
* (1.0
- $eSquared / 4.0
- 3.0 * $eSquared * $eSquared / 64.0
- 5.0
* pow($eSquared, 3.0)
/ 256.0));
$phi1Rad =
$mu
+ (3.0 * $e1 / 2.0 - 27.0 * pow($e1, 3.0) / 32.0) * sin(2.0 * $mu)
+ (21.0 * $e1 * $e1 / 16.0 - 55.0 * pow($e1, 4.0) / 32.0)
* sin(4.0 * $mu)
+ (151.0 * pow($e1, 3.0) / 96.0) * sin(6.0 * $mu);
$n =
$a
/ sqrt(1.0 - $eSquared * sin($phi1Rad) * sin($phi1Rad));
$t = tan($phi1Rad) * tan($phi1Rad);
$c = $ePrimeSquared * cos($phi1Rad) * cos($phi1Rad);
$r =
$a
* (1.0 - $eSquared)
/ pow(
1.0 - $eSquared * sin($phi1Rad) * sin($phi1Rad),
1.5);
$d = $x / ($n * $UTM_F0);
$latitude = (
$phi1Rad
- ($n * tan($phi1Rad) / $r)
* ($d * $d / 2.0
- (5.0
+ (3.0 * $t)
+ (10.0 * $c)
- (4.0 * $c * $c)
- (9.0 * $ePrimeSquared))
* pow($d, 4.0)
/ 24.0
+ (61.0
+ (90.0 * $t)
+ (298.0 * $c)
+ (45.0 * $t * $t)
- (252.0 * $ePrimeSquared)
- (3.0 * $c * $c))
* pow($d, 6.0)
/ 720.0)) * (180.0 / pi());
$longitude = $longitudeOrigin + (
($d
- (1.0 + 2.0 * $t + $c) * pow($d, 3.0) / 6.0
+ (5.0
- (2.0 * $c)
+ (28.0 * $t)
- (3.0 * $c * $c)
+ (8.0 * $ePrimeSquared)
+ (24.0 * $t * $t))
* pow($d, 5.0)
/ 120.0)
/ cos($phi1Rad)) * (180.0 / pi());
return new LatLng($latitude, $longitude);
}
}
// ================================================================== RefEll
class RefEll {
var $maj;
var $min;
var $ecc;
/**
* Create a new RefEll object to represent a reference ellipsoid
*
* @param maj the major axis
* @param min the minor axis
*/
function RefEll($maj, $min) {
$this->maj = $maj;
$this->min = $min;
$this->ecc = (($maj * $maj) - ($min * $min)) / ($maj * $maj);
}
}
// ================================================== Mathematical Functions
function sinSquared($x) {
return sin($x) * sin($x);
}
function cosSquared($x) {
return cos($x) * cos($x);
}
function tanSquared($x) {
return tan($x) * tan($x);
}
function sec($x) {
return 1.0 / cos($x);
}
/**
* Take a string formatted as a six-figure OS grid reference (e.g.
* "TG514131") and return a reference to an OSRef object that represents
* that grid reference. The first character must be H, N, S, O or T.
* The second character can be any uppercase character from A through Z
* excluding I.
*
* @param ref
* @return
* @since 2.1
*/
function getOSRefFromSixFigureReference($ref) {
$char1 = substr($ref, 0, 1);
$char2 = substr($ref, 1, 1);
$east = substr($ref, 2, 3) * 100;
$north = substr($ref, 5, 3) * 100;
if ($char1 == 'H') {
$north += 1000000;
} else if ($char1 == 'N') {
$north += 500000;
} else if ($char1 == 'O') {
$north += 500000;
$east += 500000;
} else if ($char1 == 'T') {
$east += 500000;
}
$char2ord = ord($char2);
if ($char2ord > 73) $char2ord--; // Adjust for no I
$nx = (($char2ord - 65) % 5) * 100000;
$ny = (4 - floor(($char2ord - 65) / 5)) * 100000;
return new OSRef($east + $nx, $north + $ny);
}
/**
* Work out the UTM latitude zone from the latitude
*
* @param latitude
* @return
*/
function getUTMLatitudeZoneLetter($latitude) {
if ((84 >= $latitude) && ($latitude >= 72)) return "X";
else if (( 72 > $latitude) && ($latitude >= 64)) return "W";
else if (( 64 > $latitude) && ($latitude >= 56)) return "V";
else if (( 56 > $latitude) && ($latitude >= 48)) return "U";
else if (( 48 > $latitude) && ($latitude >= 40)) return "T";
else if (( 40 > $latitude) && ($latitude >= 32)) return "S";
else if (( 32 > $latitude) && ($latitude >= 24)) return "R";
else if (( 24 > $latitude) && ($latitude >= 16)) return "Q";
else if (( 16 > $latitude) && ($latitude >= 8)) return "P";
else if (( 8 > $latitude) && ($latitude >= 0)) return "N";
else if (( 0 > $latitude) && ($latitude >= -8)) return "M";
else if (( -8 > $latitude) && ($latitude >= -16)) return "L";
else if ((-16 > $latitude) && ($latitude >= -24)) return "K";
else if ((-24 > $latitude) && ($latitude >= -32)) return "J";
else if ((-32 > $latitude) && ($latitude >= -40)) return "H";
else if ((-40 > $latitude) && ($latitude >= -48)) return "G";
else if ((-48 > $latitude) && ($latitude >= -56)) return "F";
else if ((-56 > $latitude) && ($latitude >= -64)) return "E";
else if ((-64 > $latitude) && ($latitude >= -72)) return "D";
else if ((-72 > $latitude) && ($latitude >= -80)) return "C";
else return 'Z';
}
?>