Merge pull request phayes#42 from phayes/geohash-revamp

Geohash Revamp
alecolucci · Aug 27, 2012 · f3fc207 · f3fc207
2 parents d7abcc1 + 7cf6a75
commit f3fc207
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Showing 4 changed files with 171 additions and 131 deletions.
diff --git a/lib/adapters/GeoHash.class.php b/lib/adapters/GeoHash.class.php
@@ -1,126 +1,163 @@
-<?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;
-  }
-}
+<?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, $as_grid = FALSE) {
+    $ll = $this->decode($hash);
+    if (!$as_grid) {
+      return new Point($ll['medlon'], $ll['medlat']);
+    }
+    else {
+      return new Polygon(array(
+        new LineString(array(
+          new Point($ll['minlon'], $ll['maxlat']),
+          new Point($ll['maxlon'], $ll['maxlat']),
+          new Point($ll['maxlon'], $ll['minlat']),
+          new Point($ll['minlon'], $ll['minlat']),
+          new Point($ll['minlon'], $ll['maxlat']),
+        ))
+      ));
+    }
+  }
+
+  /**
+   * 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, $precision = NULL){
+    if($geometry->geometryType() === 'Point'){
+      return $this->encodePoint($geometry, $precision);
+    } else {
+      // The geohash is the hash grid ID that fits the envelope
+      $envelope = $geometry->envelope();
+      $geohashes = array();
+      $geohash = '';
+      foreach ($envelope->getPoints() as $point) {
+        $geohashes[] = $this->encodePoint($point, 0.0000001);
+      }
+      $i = 0;
+      while ($i < strlen($geohashes[0])) {
+        $char = $geohashes[0][$i];
+        foreach ($geohashes as $hash) {
+          if ($hash[$i] != $char) {
+            return $geohash;
+          }
+        }
+        $geohash .= $char;
+        $i++;
+      }
+      return $geohash;
+    }
+  }
+
+  /**
+   * @return string geohash
+   * @param Point $point
+   * @author algorithm based on code by Alexander Songe <[email protected]>
+   * @see https://github.com/asonge/php-geohash/issues/1
+   */
+  private function encodePoint($point, $precision = NULL){
+    if ($precision === NULL) {
+      $lap = strlen($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;
+    $minlon = -180;
+    $maxlon =  180;
+    $latE   =   90;
+    $lonE   =  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 lon
+          $next = ($minlon+$maxlon)/2;
+          if($point->x()>$next) {
+            $chr |= pow(2,$b);
+            $minlon = $next;
+          } else {
+            $maxlon = $next;
+          }
+          $lonE /= 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,$lonE);
+    }
+    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();
+    $minlat =  -90;
+    $maxlat =   90;
+    $minlon = -180;
+    $maxlon =  180;
+    $latE   =   90;
+    $lonE   =  180;
+    for($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) $minlon = ($minlon+$maxlon)/2; else $maxlon = ($minlon+$maxlon)/2;
+        if(4&$v) $minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2;
+        if(2&$v) $minlon = ($minlon+$maxlon)/2; else $maxlon = ($minlon+$maxlon)/2;
+        if(1&$v) $minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2;
+        $latE /= 8;
+        $lonE /= 4;
+      } else {
+        if(16&$v)$minlon = ($minlon+$maxlon)/2; else $maxlon = ($minlon+$maxlon)/2;
+        if(8&$v) $minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2;
+        if(4&$v) $minlon = ($minlon+$maxlon)/2; else $maxlon = ($minlon+$maxlon)/2;
+        if(2&$v) $minlat = ($minlat+$maxlat)/2; else $maxlat = ($minlat+$maxlat)/2;
+        if(1&$v) $minlon = ($minlon+$maxlon)/2; else $maxlon = ($minlon+$maxlon)/2;
+        $latE /= 4;
+        $lonE /= 8;
+      }
+    }
+    $ll['minlat'] = $minlat;
+    $ll['minlon'] = $minlon;
+    $ll['maxlat'] = $maxlat;
+    $ll['maxlon'] = $maxlon;
+    $ll['medlat'] = round(($minlat+$maxlat)/2, max(1, -round(log10($latE)))-1);
+    $ll['medlon'] = round(($minlon+$maxlon)/2, max(1, -round(log10($lonE)))-1);
+    return $ll;
+  }
+}
diff --git a/tests/input/long.geohash b/tests/input/long.geohash
@@ -0,0 +1 @@
+xn76urx4epb0
diff --git a/tests/input/short.geohash b/tests/input/short.geohash
@@ -0,0 +1 @@
+xpssc0
diff --git a/tests/test.php b/tests/test.php
@@ -1,7 +1,7 @@
 <?php
 
 // Uncomment to test
-// run_test();
+# run_test();
 
 function run_test() {
   header("Content-type: text");
@@ -120,8 +120,11 @@ function test_adapters($geometry, $format, $input) {
         $test_geom_2 = $adapter_loader->read($test_geom_1->out($adapter_key));
 
         // Check to make sure a round-trip results in the same geometry
-        if ($test_geom_1->out('wkt') != $test_geom_2->out('wkt')) {
-          print "Mismatched adapter output in ".$adapter_class."\n";
+        // We don't check round-trip accuracy on geohash as it's not a storage format that preserves information
+        if ($adapter_key != 'geohash') {
+          if ($test_geom_1->out('wkt') != $test_geom_2->out('wkt')) {
+            print "Mismatched adapter output in ".$adapter_class."\n";
+          }
         }
       }
       else {
@@ -197,8 +200,6 @@ function test_methods($geometry) {
 
     if ($geos_type != $norm_type) {
       print 'Type mismatch on '.$method."\n";
-      var_dump($geos_type);
-      var_dump($norm_type);
       continue;
     }