Merge branch 'master' of github.com:phayes/geoPHP

geoPHP.inc

@@ -18,6 +18,7 @@ include_once("lib/adapters/KML.class.php");
 include_once("lib/adapters/GPX.class.php");
 include_once("lib/adapters/GeoRSS.class.php");
 include_once("lib/adapters/GoogleGeocode.class.php");
+include_once("lib/adapters/GeoHash.class.php");
 
 // Geometries
 include_once("lib/geometry/Geometry.class.php"); // Abtract class
@@ -83,6 +84,7 @@ class geoPHP
       'gpx' =>  'GPX',
       'georss' => 'GeoRSS',
       'google_geocode' => 'GoogleGeocode',
+      'geohash' => 'GeoHash',
     );
   }
 

lib/adapters/GeoHash.class.php

@@ -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;
+  }
+}