forked from lino/radar-wp
249 lines
7.3 KiB
PHP
249 lines
7.3 KiB
PHP
<?php
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/**
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* PHP Geometry GeoHash encoder/decoder.
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*
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* @author prinsmc
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* @see http://en.wikipedia.org/wiki/Geohash
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*
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*/
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class GeoHash extends GeoAdapter{
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/**
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* base32 encoding character map.
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*/
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private $table = "0123456789bcdefghjkmnpqrstuvwxyz";
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/**
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* array of neighbouring hash character maps.
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*/
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private $neighbours = array (
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// north
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'top' => array (
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'even' => 'p0r21436x8zb9dcf5h7kjnmqesgutwvy',
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'odd' => 'bc01fg45238967deuvhjyznpkmstqrwx'
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),
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// east
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'right' => array (
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'even' => 'bc01fg45238967deuvhjyznpkmstqrwx',
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'odd' => 'p0r21436x8zb9dcf5h7kjnmqesgutwvy'
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),
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// west
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'left' => array (
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'even' => '238967debc01fg45kmstqrwxuvhjyznp',
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'odd' => '14365h7k9dcfesgujnmqp0r2twvyx8zb'
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),
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// south
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'bottom' => array (
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'even' => '14365h7k9dcfesgujnmqp0r2twvyx8zb',
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'odd' => '238967debc01fg45kmstqrwxuvhjyznp'
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)
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);
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/**
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* array of bordering hash character maps.
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*/
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private $borders = array (
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// north
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'top' => array (
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'even' => 'prxz',
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'odd' => 'bcfguvyz'
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),
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// east
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'right' => array (
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'even' => 'bcfguvyz',
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'odd' => 'prxz'
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),
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// west
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'left' => array (
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'even' => '0145hjnp',
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'odd' => '028b'
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),
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// south
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'bottom' => array (
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'even' => '028b',
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'odd' => '0145hjnp'
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)
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);
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/**
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* Convert the geohash to a Point. The point is 2-dimensional.
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* @return Point the converted geohash
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* @param string $hash a geohash
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* @see GeoAdapter::read()
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*/
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public function read($hash, $as_grid = FALSE) {
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$ll = $this->decode($hash);
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if (!$as_grid) {
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return new Point($ll['medlon'], $ll['medlat']);
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}
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else {
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return new Polygon(array(
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new LineString(array(
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new Point($ll['minlon'], $ll['maxlat']),
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new Point($ll['maxlon'], $ll['maxlat']),
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new Point($ll['maxlon'], $ll['minlat']),
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new Point($ll['minlon'], $ll['minlat']),
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new Point($ll['minlon'], $ll['maxlat']),
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))
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));
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}
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}
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/**
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* Convert the geometry to geohash.
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* @return string the geohash or null when the $geometry is not a Point
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* @param Point $geometry
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* @see GeoAdapter::write()
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*/
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public function write(Geometry $geometry, $precision = NULL){
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if ($geometry->isEmpty()) return '';
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if($geometry->geometryType() === 'Point'){
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return $this->encodePoint($geometry, $precision);
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}
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else {
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// The geohash is the hash grid ID that fits the envelope
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$envelope = $geometry->envelope();
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$geohashes = array();
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$geohash = '';
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foreach ($envelope->getPoints() as $point) {
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$geohashes[] = $this->encodePoint($point, 0.0000001);
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}
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$i = 0;
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while ($i < strlen($geohashes[0])) {
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$char = $geohashes[0][$i];
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foreach ($geohashes as $hash) {
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if ($hash[$i] != $char) {
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return $geohash;
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}
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}
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$geohash .= $char;
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$i++;
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}
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return $geohash;
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}
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}
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/**
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* @return string geohash
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* @param Point $point
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* @author algorithm based on code by Alexander Songe <a@songe.me>
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* @see https://github.com/asonge/php-geohash/issues/1
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*/
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private function encodePoint($point, $precision = NULL){
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if ($precision === NULL) {
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$lap = strlen($point->y())-strpos($point->y(),".");
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$lop = strlen($point->x())-strpos($point->x(),".");
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$precision = pow(10,-max($lap-1,$lop-1,0))/2;
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}
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$minlat = -90;
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$maxlat = 90;
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$minlon = -180;
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$maxlon = 180;
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$latE = 90;
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$lonE = 180;
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$i = 0;
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$error = 180;
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$hash='';
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while($error>=$precision) {
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$chr = 0;
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for($b=4;$b>=0;--$b) {
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if((1&$b) == (1&$i)) {
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// even char, even bit OR odd char, odd bit...a lon
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$next = ($minlon+$maxlon)/2;
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if($point->x()>$next) {
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$chr |= pow(2,$b);
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$minlon = $next;
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} else {
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$maxlon = $next;
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}
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$lonE /= 2;
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} else {
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// odd char, even bit OR even char, odd bit...a lat
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$next = ($minlat+$maxlat)/2;
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if($point->y()>$next) {
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$chr |= pow(2,$b);
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$minlat = $next;
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} else {
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$maxlat = $next;
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}
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$latE /= 2;
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}
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}
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$hash .= $this->table[$chr];
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$i++;
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$error = min($latE,$lonE);
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}
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return $hash;
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}
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/**
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* @param string $hash a geohash
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* @author algorithm based on code by Alexander Songe <a@songe.me>
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* @see https://github.com/asonge/php-geohash/issues/1
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*/
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private function decode($hash){
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$ll = array();
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$minlat = -90;
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$maxlat = 90;
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$minlon = -180;
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$maxlon = 180;
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$latE = 90;
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$lonE = 180;
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for($i=0,$c=strlen($hash);$i<$c;$i++) {
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$v = strpos($this->table,$hash[$i]);
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if(1&$i) {
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if(16&$v)$minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2;
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if(8&$v) $minlon = ($minlon+$maxlon)/2; else $maxlon = ($minlon+$maxlon)/2;
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if(4&$v) $minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2;
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if(2&$v) $minlon = ($minlon+$maxlon)/2; else $maxlon = ($minlon+$maxlon)/2;
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if(1&$v) $minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2;
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$latE /= 8;
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$lonE /= 4;
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} else {
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if(16&$v)$minlon = ($minlon+$maxlon)/2; else $maxlon = ($minlon+$maxlon)/2;
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if(8&$v) $minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2;
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if(4&$v) $minlon = ($minlon+$maxlon)/2; else $maxlon = ($minlon+$maxlon)/2;
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if(2&$v) $minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2;
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if(1&$v) $minlon = ($minlon+$maxlon)/2; else $maxlon = ($minlon+$maxlon)/2;
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$latE /= 4;
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$lonE /= 8;
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}
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}
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$ll['minlat'] = $minlat;
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$ll['minlon'] = $minlon;
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$ll['maxlat'] = $maxlat;
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$ll['maxlon'] = $maxlon;
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$ll['medlat'] = round(($minlat+$maxlat)/2, max(1, -round(log10($latE)))-1);
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$ll['medlon'] = round(($minlon+$maxlon)/2, max(1, -round(log10($lonE)))-1);
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return $ll;
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}
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/**
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* Calculates the adjacent geohash of the geohash in the specified direction.
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* This algorithm is available in various ports that seem to point back to
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* geohash-js by David Troy under MIT notice.
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*
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*
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* @see https://github.com/davetroy/geohash-js
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* @see https://github.com/lyokato/objc-geohash
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* @see https://github.com/lyokato/libgeohash
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* @see https://github.com/masuidrive/pr_geohash
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* @see https://github.com/sunng87/node-geohash
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* @see https://github.com/davidmoten/geo
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*
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* @param string $hash the geohash (lowercase)
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* @param string $direction the direction of the neighbor (top, bottom, left or right)
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* @return string the geohash of the adjacent cell
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*/
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public function adjacent($hash, $direction){
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$last = substr($hash, -1);
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$type = (strlen($hash) % 2)? 'odd': 'even';
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$base = substr($hash, 0, strlen($hash) - 1);
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if(strpos(($this->borders[$direction][$type]), $last) !== false){
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$base = $this->adjacent($base, $direction);
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}
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return $base.$this->table[strpos($this->neighbours[$direction][$type], $last)];
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}
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}
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