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<?php |
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namespace geoPHP\Adapter; |
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use geoPHP\Geometry\Geometry; |
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use geoPHP\Geometry\Point; |
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use geoPHP\Geometry\LineString; |
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use geoPHP\Geometry\Polygon; |
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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 implements GeoAdapter |
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{ |
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/** |
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* @var string |
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* @noinspection SpellCheckingInspection */ |
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public static $characterTable = "0123456789bcdefghjkmnpqrstuvwxyz"; |
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/** |
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* @var array<string, array<string,string>> of neighbouring hash character maps. |
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*/ |
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private static $neighbours = [ |
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// north |
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'top' => [ |
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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' => [ |
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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' => [ |
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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' => [ |
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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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* @var array<string, array<string,string>> of bordering hash character maps. |
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*/ |
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private static $borders = [ |
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// north |
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'top' => [ |
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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' => [ |
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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' => [ |
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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' => [ |
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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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* |
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* @param string $hash a GeoHash |
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* @param bool $asGrid Return the center point of hash grid or the grid cell as Polygon |
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* @return Point|Polygon the converted GeoHash |
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*/ |
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public function read(string $hash, bool $asGrid = false): Geometry |
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{ |
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$decodedHash = $this->decode($hash); |
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if (!$asGrid) { |
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return new Point($decodedHash['centerLongitude'], $decodedHash['centerLatitude']); |
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} |
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return new Polygon( |
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[ |
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new LineString( |
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[ |
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new Point($decodedHash['minLongitude'], $decodedHash['maxLatitude']), |
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new Point($decodedHash['maxLongitude'], $decodedHash['maxLatitude']), |
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new Point($decodedHash['maxLongitude'], $decodedHash['minLatitude']), |
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new Point($decodedHash['minLongitude'], $decodedHash['minLatitude']), |
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new Point($decodedHash['minLongitude'], $decodedHash['maxLatitude']), |
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] |
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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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* |
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* @param Geometry $geometry |
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* @param float|null $precision default 0.0000001 |
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* @return string the GeoHash or null when the $geometry is not a Point |
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*/ |
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public function write(Geometry $geometry, $precision = 0.0000001): string |
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{ |
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if ($geometry->isEmpty()) { |
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return ''; |
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} |
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if ($geometry->geometryType() === Geometry::POINT) { |
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/** @var Point $geometry */ |
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return $this->encodePoint($geometry, $precision); |
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} |
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// The GeoHash is the smallest hash grid ID that fits the envelope |
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$envelope = $geometry->envelope(); |
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if ($envelope === null) { |
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return ''; |
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} |
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$geoHashes = []; |
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$geohash = ''; |
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foreach ($envelope->getPoints() as $point) { |
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$geoHashes[] = $this->encodePoint($point, $precision); |
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} |
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$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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* algorithm based on code by Alexander Songe |
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* @author Alexander Songe <[email protected]> |
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* @see https://github.com/asonge/php-geohash/issues/1 |
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* |
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* @param Point $point |
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* @param float|null $precision |
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* @return string The GeoHash |
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* @throws \Exception |
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*/ |
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private function encodePoint($point, $precision = null) |
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{ |
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$minLatitude = -90.0000000000001; |
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$maxLatitude = 90.0000000000001; |
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$minLongitude = -180.0000000000001; |
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$maxLongitude = 180.0000000000001; |
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$latitudeError = 90; |
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$longitudeError = 180; |
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$i = 0; |
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$error = 180; |
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$hash = ''; |
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$x = $point->getX(); |
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$y = $point->getY(); |
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if (!is_numeric($precision)) { |
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$lap = strlen(strval($y)) - strpos(strval($y), "."); |
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$lop = strlen(strval($x)) - strpos(strval($x), "."); |
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$precision = pow(10, -max($lap - 1, $lop - 1, 0)) / 2; |
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} |
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if ($x < $minLongitude || $y < $minLatitude || |
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$x > $maxLongitude || $y > $maxLatitude |
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) { |
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throw new \Exception("Point coordinates (" . $x . ", " . $y . ") are out of lat/lon range"); |
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} |
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while ($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 = ($minLongitude + $maxLongitude) / 2; |
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if ($x > $next) { |
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$chr |= pow(2, $b); |
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$minLongitude = $next; |
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} else { |
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$maxLongitude = $next; |
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} |
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$longitudeError /= 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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$next = ($minLatitude + $maxLatitude) / 2; |
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if ($y > $next) { |
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$chr |= pow(2, $b); |
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$minLatitude = $next; |
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} else { |
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$maxLatitude = $next; |
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} |
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$latitudeError /= 2; |
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} |
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} |
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$hash .= self::$characterTable[$chr]; |
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$i++; |
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$error = min($latitudeError, $longitudeError); |
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} |
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return $hash; |
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} |
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/** |
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* algorithm based on code by Alexander Songe |
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* @author Alexander Songe <[email protected]> |
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* @see https://github.com/asonge/php-geohash/issues/1 |
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* |
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* @param string $hash a GeoHash |
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* @return array<string, int|float> Associative array. |
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*/ |
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private function decode($hash): array |
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{ |
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$result = []; |
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$minLatitude = -90; |
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$maxLatitude = 90; |
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$minLongitude = -180; |
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$maxLongitude = 180; |
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$latitudeError = 90; |
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$longitudeError = 180; |
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for ($i = 0, $c = strlen($hash); $i < $c; $i++) { |
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$v = strpos(self::$characterTable, $hash[$i]); |
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if (1 & $i) { |
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if (16 & $v) { |
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$minLatitude = ($minLatitude + $maxLatitude) / 2; |
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} else { |
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$maxLatitude = ($minLatitude + $maxLatitude) / 2; |
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} |
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if (8 & $v) { |
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$minLongitude = ($minLongitude + $maxLongitude) / 2; |
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} else { |
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$maxLongitude = ($minLongitude + $maxLongitude) / 2; |
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} |
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if (4 & $v) { |
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$minLatitude = ($minLatitude + $maxLatitude) / 2; |
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} else { |
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$maxLatitude = ($minLatitude + $maxLatitude) / 2; |
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} |
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if (2 & $v) { |
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$minLongitude = ($minLongitude + $maxLongitude) / 2; |
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} else { |
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$maxLongitude = ($minLongitude + $maxLongitude) / 2; |
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} |
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if (1 & $v) { |
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$minLatitude = ($minLatitude + $maxLatitude) / 2; |
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} else { |
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$maxLatitude = ($minLatitude + $maxLatitude) / 2; |
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} |
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$latitudeError /= 8; |
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$longitudeError /= 4; |
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} else { |
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if (16 & $v) { |
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$minLongitude = ($minLongitude + $maxLongitude) / 2; |
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} else { |
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$maxLongitude = ($minLongitude + $maxLongitude) / 2; |
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} |
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if (8 & $v) { |
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$minLatitude = ($minLatitude + $maxLatitude) / 2; |
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} else { |
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$maxLatitude = ($minLatitude + $maxLatitude) / 2; |
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} |
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if (4 & $v) { |
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$minLongitude = ($minLongitude + $maxLongitude) / 2; |
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} else { |
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$maxLongitude = ($minLongitude + $maxLongitude) / 2; |
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} |
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if (2 & $v) { |
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$minLatitude = ($minLatitude + $maxLatitude) / 2; |
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} else { |
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$maxLatitude = ($minLatitude + $maxLatitude) / 2; |
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} |
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if (1 & $v) { |
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$minLongitude = ($minLongitude + $maxLongitude) / 2; |
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} else { |
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$maxLongitude = ($minLongitude + $maxLongitude) / 2; |
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} |
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$latitudeError /= 4; |
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$longitudeError /= 8; |
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} |
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} |
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$result['minLatitude'] = $minLatitude; |
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$result['minLongitude'] = $minLongitude; |
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$result['maxLatitude'] = $maxLatitude; |
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$result['maxLongitude'] = $maxLongitude; |
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$result['centerLatitude'] = round(($minLatitude + $maxLatitude) / 2, (int) max(1, -round(log10($latitudeError))) - 1); |
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$result['centerLongitude'] = round(($minLongitude + $maxLongitude) / 2, (int) max(1, -round(log10($longitudeError))) - 1); |
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return $result; |
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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 $direction the direction of the neighbor (top, bottom, left or right) |
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* @return string the geohash of the adjacent cell |
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*/ |
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public static function adjacent($hash, $direction) |
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{ |
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$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((self::$borders[$direction][$type]), $last) !== false) { |
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$base = self::adjacent($base, $direction); |
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} |
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return $base . self::$characterTable[strpos(self::$neighbours[$direction][$type], $last)]; |
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} |
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} |
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