/**
* <p>Computes the bounding coordinates of all points on the surface
* of a sphere that have a great circle distance to the point represented
* by this GeoLocation instance that is less or equal to the distance
* argument.</p>
* <p>For more information about the formulae used in this method visit
* <a href="http://JanMatuschek.de/LatitudeLongitudeBoundingCoordinates">
* http://JanMatuschek.de/LatitudeLongitudeBoundingCoordinates</a>.</p>
*
* @param double $distance the distance from the point represented by this
* GeoLocation instance. Must me measured in the same unit as the radius
* argument.
* @param string $unit_of_measurement
* @throws \Exception
* @internal param radius the radius of the sphere, e.g. the average radius for a
* spherical approximation of the figure of the Earth is approximately
* 6371.01 kilometers.
* @return GeoLocation[] an array of two GeoLocation objects such that:<ul>
* <li>The latitude of any point within the specified distance is greater
* or equal to the latitude of the first array element and smaller or
* equal to the latitude of the second array element.</li>
* <li>If the longitude of the first array element is smaller or equal to
* the longitude of the second element, then
* the longitude of any point within the specified distance is greater
* or equal to the longitude of the first array element and smaller or
* equal to the longitude of the second array element.</li>
* <li>If the longitude of the first array element is greater than the
* longitude of the second element (this is the case if the 180th
* meridian is within the distance), then
* the longitude of any point within the specified distance is greater
* or equal to the longitude of the first array element
* <strong>or</strong> smaller or equal to the longitude of the second
* array element.</li>
* </ul>
*/
public function boundingCoordinates($distance, $unit_of_measurement) {
$radius = $this->getEarthsRadius($unit_of_measurement);
if ($radius < 0 || $distance < 0) throw new \Exception('Arguments must be greater than 0.');
// angular distance in radians on a great circle
$this->angular = $distance / $radius;
$minLat = $this->radLat - $this->angular;
$maxLat = $this->radLat + $this->angular;
$minLon = 0;
$maxLon = 0;
if ($minLat > self::$MIN_LAT && $maxLat < self::$MAX_LAT) {
$deltaLon = asin(sin($this->angular) /
cos($this->radLat));
$minLon = $this->radLon - $deltaLon;
if ($minLon < self::$MIN_LON) $minLon += 2 * pi();
$maxLon = $this->radLon + $deltaLon;
if ($maxLon > self::$MAX_LON) $maxLon -= 2 * pi();
} else {
// a pole is within the distance
$minLat = max($minLat, self::$MIN_LAT);
$maxLat = min($maxLat, self::$MAX_LAT);
$minLon = self::$MIN_LON;
$maxLon = self::$MAX_LON;
}
return array(
GeoLocation::fromRadians($minLat, $minLon),
GeoLocation::fromRadians($maxLat, $maxLon)
);
}
/**
* <p>Computes the bounding coordinates of all points on the surface
* of a sphere that have a great circle distance to the point represented
* by this GeoLocation instance that is less or equal to the distance
* argument.</p>
* <p>For more information about the formulae used in this method visit
* <a href="http://JanMatuschek.de/LatitudeLongitudeBoundingCoordinates">
* http://JanMatuschek.de/LatitudeLongitudeBoundingCoordinates</a>.</p>
* @param distance the distance from the point represented by this
* GeoLocation instance. Must me measured in the same unit as the radius
* argument.
* @param radius the radius of the sphere, e.g. the average radius for a
* spherical approximation of the figure of the Earth is approximately
* 6371.01 kilometers.
* @return an array of two GeoLocation objects such that:<ul>
* <li>The latitude of any point within the specified distance is greater
* or equal to the latitude of the first array element and smaller or
* equal to the latitude of the second array element.</li>
* <li>If the longitude of the first array element is smaller or equal to
* the longitude of the second element, then
* the longitude of any point within the specified distance is greater
* or equal to the longitude of the first array element and smaller or
* equal to the longitude of the second array element.</li>
* <li>If the longitude of the first array element is greater than the
* longitude of the second element (this is the case if the 180th
* meridian is within the distance), then
* the longitude of any point within the specified distance is greater
* or equal to the longitude of the first array element
* <strong>or</strong> smaller or equal to the longitude of the second
* array element.</li>
* </ul>
*/
public function boundingCoordinates($distance, $radius)
{
if ($radius < 0 || $distance < 0) {
throw new Exception('Arguments must be greater than 0.');
}
// angular distance in radians on a great circle
$radDist = $distance / $radius;
$minLat = $this->radLat - $radDist;
$maxLat = $this->radLat + $radDist;
$minLon = 0;
$maxLon = 0;
if ($minLat > MIN_LAT && $maxLat < MAX_LAT) {
$deltaLon = asin(sin($radDist) / cos($this->radLat));
$minLon = $this->radLon - $deltaLon;
if ($minLon < MIN_LON) {
$minLon += 2 * pi();
}
$maxLon = $this->radLon + $deltaLon;
if ($maxLon > MAX_LON) {
$maxLon -= 2 * pi();
}
} else {
// a pole is within the distance
$minLat = max($minLat, MIN_LAT);
$maxLat = min($maxLat, MAX_LAT);
$minLon = MIN_LON;
$maxLon = MAX_LON;
}
return array(GeoLocation::fromRadians($minLat, $minLon), GeoLocation::fromRadians($maxLat, $maxLon));
}
