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<?php |
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namespace Nubs\Coordinator\CoordinateSystem; |
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use Nubs\Coordinator\CoordinateFactory; |
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use Nubs\Coordinator\Spheroid; |
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class Mercator |
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{ |
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/** |
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* The spheroid being referenced. |
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* |
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* @var \Nubs\Coordinator\Spheroid |
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*/ |
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private $_spheroid; |
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/** |
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* The coordinate factory. |
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* |
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* @var \Nubs\Coordinator\CoordinateFactory |
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*/ |
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private $_coordinateFactory; |
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/** |
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* Initialize a Mercator Coordinate System for the given spheroid. |
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* |
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* @param \Nubs\Coordinator\Spheroid $spheroid The spheroid being referenced. |
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* @param \Nubs\Coordinator\CoordinateFactory $coordinateFactory The coordinate factory |
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*/ |
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public function __construct(Spheroid $spheroid, CoordinateFactory $coordinateFactory) |
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{ |
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$this->_spheroid = $spheroid; |
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$this->_coordinateFactory = $coordinateFactory; |
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} |
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/** |
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* Load a coordinate from the mercator coordinates. |
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* |
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* This uses a spherical model of the spheroid. |
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* |
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* @param float $x The x coordinate. |
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* @param float $y The y coordinate. |
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* @return \Nubs\Coordinator\Coordinate The coordinate after conversion. |
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*/ |
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public function loadCoordinate($x, $y) |
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{ |
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$radius = $this->_spheroid->equatorialRadius(); |
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return $this->_coordinateFactory->createFromRadians($this->_gudermannian($y / $radius), $x / $radius); |
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} |
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/** |
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* Compute the Gudermannian of the given number. |
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* |
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* @see http://en.wikipedia.org/wiki/Gudermannian_function |
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* |
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* Useful for computing the latitude in radians when given the latitudinal distance from the equator. |
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* |
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* @param float $x |
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* @return float |
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*/ |
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private function _gudermannian($x) |
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{ |
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return atan(sinh($x)); |
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} |
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} |
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nubs /
coordinator
