/**
* Get the Radius of Curvature along the Prime Vertical at a specified latitude
* for this Reference Ellipsoid object
*
* The formula used here is from http://www.epsg.org/guides/docs/G7-2.pdf
*
* @param integer|float $latitude Angle of Latitude for the Radius of Curvature,
* positive when to the north of the equator, negative when to the south
* @param string $degrad Indicating whether the Angle of Latitude is being specified
* in degrees or radians
* @param string $uom Unit of Measure for the returned value
* @return float The Radius of Curvature along the Prime Vertical at the specified latitude
* for this ellipsoid
* @throws Exception
*/
public function getRadiusOfCurvaturePrimeVertical($latitude = null, $degrad = Angle::DEGREES, $uom = Distance::METRES)
{
$latitude = LatLong::validateLatitude($latitude, $degrad);
if ($this->dirty) {
$this->calculateDerivedParameters();
}
$radius = $this->semiMajorAxis->getValue() / pow(1 - $this->firstEccentricitySquared * self::sinSquared($latitude), 0.5);
return Distance::convertFromMeters($radius, $uom);
}