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Merge pull request phayes#39 from mprins/geohash
adding GeoHash adapter
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,126 @@ | ||
| <?php | ||
| /** | ||
| * PHP Geometry GeoHash encoder/decoder. | ||
| * | ||
| * @author prinsmc | ||
| * @see http://en.wikipedia.org/wiki/Geohash | ||
| * | ||
| */ | ||
| class GeoHash extends GeoAdapter{ | ||
| private $table = "0123456789bcdefghjkmnpqrstuvwxyz"; | ||
|
|
||
| /** | ||
| * Convert the geohash to a Point. The point is 2-dimensional. | ||
| * @return Point the converted geohash | ||
| * @param string $hash a geohash | ||
| * @see GeoAdapter::read() | ||
| */ | ||
| public function read($hash) { | ||
| $ll = $this->decode($hash); | ||
| return new Point($ll['lon'], $ll['lat'], NULL); | ||
| } | ||
|
|
||
| /** | ||
| * Convert the geometry to geohash. | ||
| * @return string the geohash or null when the $geometry is not a Point | ||
| * @param Point $geometry | ||
| * @see GeoAdapter::write() | ||
| */ | ||
| public function write(Geometry $geometry){ | ||
| if($geometry->geometryType()==='Point'){ | ||
| return $this->encode($geometry); | ||
| } else { | ||
| return NULL; | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * @return string geohash | ||
| * @param Point $point | ||
| * @author algorithm based on code by Alexander Songe <[email protected]> | ||
| * @see https://github.com/asonge/php-geohash/issues/1 | ||
| */ | ||
| private function encode($point){ | ||
| $lap = strlen($point->y())-strpos($point->y(),"."); | ||
| $lop = strlen($point->x())-strpos($point->x(),"."); | ||
| $precision = pow(10,-max($lap-1,$lop-1,0))/2; | ||
|
|
||
| $minlat = -90; | ||
| $maxlat = 90; | ||
| $minlng = -180; | ||
| $maxlng = 180; | ||
| $latE = 90; | ||
| $lngE = 180; | ||
| $i = 0; | ||
| $error = 180; | ||
| $hash=''; | ||
| while($error>=$precision) { | ||
| $chr = 0; | ||
| for($b=4;$b>=0;--$b) { | ||
| if((1&$b) == (1&$i)) { | ||
| // even char, even bit OR odd char, odd bit...a lng | ||
| $next = ($minlng+$maxlng)/2; | ||
| if($point->x()>$next) { | ||
| $chr |= pow(2,$b); | ||
| $minlng = $next; | ||
| } else { | ||
| $maxlng = $next; | ||
| } | ||
| $lngE /= 2; | ||
| } else { | ||
| // odd char, even bit OR even char, odd bit...a lat | ||
| $next = ($minlat+$maxlat)/2; | ||
| if($point->y()>$next) { | ||
| $chr |= pow(2,$b); | ||
| $minlat = $next; | ||
| } else { | ||
| $maxlat = $next; | ||
| } | ||
| $latE /= 2; | ||
| } | ||
| } | ||
| $hash .= $this->table[$chr]; | ||
| $i++; | ||
| $error = min($latE,$lngE); | ||
| } | ||
| return $hash; | ||
| } | ||
|
|
||
| /** | ||
| * @param string $hash a geohash | ||
| * @author algorithm based on code by Alexander Songe <[email protected]> | ||
| * @see https://github.com/asonge/php-geohash/issues/1 | ||
| */ | ||
| private function decode($hash){ | ||
| $ll = array('lat'=>NULL,'lon'=>NULL); | ||
| $minlat = -90; | ||
| $maxlat = 90; | ||
| $minlng = -180; | ||
| $maxlng = 180; | ||
| $latE = 90; | ||
| $lngE = 180; | ||
| for($i=0,$c=strlen($hash);$i<$c;$i++) { | ||
| $v = strpos($this->table,$hash[$i]); | ||
| if(1&$i) { | ||
| if(16&$v)$minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2; | ||
| if(8&$v) $minlng = ($minlng+$maxlng)/2; else $maxlng = ($minlng+$maxlng)/2; | ||
| if(4&$v) $minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2; | ||
| if(2&$v) $minlng = ($minlng+$maxlng)/2; else $maxlng = ($minlng+$maxlng)/2; | ||
| if(1&$v) $minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2; | ||
| $latE /= 8; | ||
| $lngE /= 4; | ||
| } else { | ||
| if(16&$v)$minlng = ($minlng+$maxlng)/2; else $maxlng = ($minlng+$maxlng)/2; | ||
| if(8&$v) $minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2; | ||
| if(4&$v) $minlng = ($minlng+$maxlng)/2; else $maxlng = ($minlng+$maxlng)/2; | ||
| if(2&$v) $minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2; | ||
| if(1&$v) $minlng = ($minlng+$maxlng)/2; else $maxlng = ($minlng+$maxlng)/2; | ||
| $latE /= 4; | ||
| $lngE /= 8; | ||
| } | ||
| } | ||
| $ll['lat'] = round(($minlat+$maxlat)/2, max(1, -round(log10($latE)))-1); | ||
| $ll['lon'] = round(($minlng+$maxlng)/2, max(1, -round(log10($lngE)))-1); | ||
| return $ll; | ||
| } | ||
| } |