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<?php |
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namespace MatthiasMullie\Geo; |
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/** |
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* Please report bugs on https://github.com/matthiasmullie/geo/issues |
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* |
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* @author Matthias Mullie <[email protected]> |
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* |
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* @copyright Copyright (c) 2013, Matthias Mullie. All rights reserved. |
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* @license MIT License |
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*/ |
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class Geo |
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{ |
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/** |
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* Earth's mean radii. |
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* Note that earth is not exactly round and so calculations will always be |
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* slightly off. |
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* |
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* @see http://en.wikipedia.org/wiki/Earth_radius |
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* @var float[] |
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*/ |
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protected $radii = array( |
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// metric |
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'km' => 6371, |
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'hm' => 63710, // km * 10 |
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'dam' => 637100, // km * 100 |
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'm' => 6371000, // km * 1000 |
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'dm' => 63710000, // km * 10000 |
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'cm' => 637100000, // km * 100000 |
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'mm' => 6371000000, // km * 1000000 |
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// imperial (https://en.wikipedia.org/wiki/Imperial_units) |
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'mi' => 3959, |
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'fur' => 31672, // mi * 8 |
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'ch' => 316720, // mi * 80 |
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'yd' => 6967840, // mi * 1760 |
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'ft' => 20903520, // mi * 5280 |
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'in' => 250842240, // mi * 63360 |
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); |
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/** |
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* @var string |
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*/ |
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protected $unit; |
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/** |
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* @var float |
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*/ |
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protected $radius; |
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/** |
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* @param string[optional] $unit e.g. km (kilometers) or mi (miles) |
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* @throws Exception |
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*/ |
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public function __construct($unit = 'km') |
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{ |
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$unit = strtolower($unit); |
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// doublecheck if given unit is valid |
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$units = array_keys($this->radii); |
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if (!in_array($unit, $units)) { |
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throw new Exception("Distance unit $unit is invalid. Valid units: ".implode(', ', $units)); |
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} |
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$this->unit = $unit; |
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$this->setRadius(); |
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} |
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/** |
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* Allows to override radius. |
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* If null, radius will be reset to the default for the given unit. |
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* |
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* @param float[optional] $radius |
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*/ |
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public function setRadius($radius = null) |
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{ |
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if ($radius === null) { |
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$radius = $this->radii[$this->unit]; |
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} |
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$this->radius = $radius; |
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} |
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/** |
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* @see http://en.wikipedia.org/wiki/Great-circle_distance |
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* @param Coordinate $coord1 First coordinate |
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* @param Coordinate $coord2 Second coordinate |
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* @return float Actual distance in human readable format (e.g. km or mi) |
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*/ |
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public function distance(Coordinate $coord1, Coordinate $coord2) |
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{ |
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// convert latitude/longitude degrees for both coordinates |
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// to radians: radian = degree * π / 180 |
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$lat1 = deg2rad($coord1->latitude); |
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$lng1 = deg2rad($coord1->longitude); |
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$lat2 = deg2rad($coord2->latitude); |
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$lng2 = deg2rad($coord2->longitude); |
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// calculate great-circle distance |
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$distance = acos(sin($lat1) * sin($lat2) + cos($lat1) * cos($lat2) * cos($lng1 - $lng2)); |
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// distance in given format |
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return $this->radius * $distance; |
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} |
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/** |
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* This calculates the boundary at $distance north, east, south & west from |
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* $coord. |
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* |
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* This can be used to easily query a database for coordinate within certain |
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* boundaries, like this: |
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* SELECT * |
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* FROM coordinates |
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* WHERE |
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* lat BETWEEN :swlat AND :nelat |
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* lng BETWEEN :swlng AND :nelng |
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* |
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* :swlat being $bounds->sw->latitude |
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* :swlng being $bounds->sw->longitude |
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* :nelat being $bounds->ne->latitude |
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* :nelng being $bounds->ne->longitude |
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* |
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* We only need 2 opposite corners in a rectangle to know all 4 boundaries, |
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* in this case the northeast & southwest coordinate. The northwest |
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* coordinate, for example, will have the same latitude as the southwest |
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* coordinate, and the same latitude as the northeast coordinate. |
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* |
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* @param Coordinate $coord Coordinate to generate bounds for |
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* @param float $distance Distance in human readable format (e.g. km or mi) |
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* @return Bounds |
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*/ |
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public function bounds(Coordinate $coord, $distance) |
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{ |
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// simple sanity check: distance cannot be greater than radius |
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if ($distance > $this->radius) { |
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$distance = $this->radius; |
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} |
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// latitude boundaries |
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$neLat = $coord->latitude + rad2deg($distance / $this->radius); |
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$swLat = $coord->latitude - rad2deg($distance / $this->radius); |
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// longitude boundaries (longitude gets smaller when latitude increases) |
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$neLng = $coord->longitude + rad2deg($distance / $this->radius / cos(deg2rad($coord->latitude))); |
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$swLng = $coord->longitude - rad2deg($distance / $this->radius / cos(deg2rad($coord->latitude))); |
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return new Bounds( |
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new Coordinate($neLat, $neLng), |
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new Coordinate($swLat, $swLng) |
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); |
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} |
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} |
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matthiasmullie /
geo
