eu.shiftforward.apso.Geo.scala Maven / Gradle / Ivy
package eu.shiftforward.apso
import scala.math.{ abs, acos, cos, sin, toRadians }
/**
* Object containing geo-location functions.
*/
object Geo {
/**
* A pair of `Double` representing, respectively, the latitude and longitude of a position.
*/
type Coordinates = (Double, Double)
private[this] val EARTH_RADIUS = 6371.009 // kilometers
/**
* Returns the distance in kilometers between two points on the planet Earth, calculated by the
* spherical law of cosines (https://en.wikipedia.org/wiki/Great-circle_distance#Formulas).
* @param p1 the coordinates of the first point
* @param p2 the coordinates of the second point
* @return the distance in kilometers between two points on the planet Earth.
*/
def distance(p1: Coordinates, p2: Coordinates) =
distanceFrom(p1)(p2)
/**
* Returns a function that measures the distance to the point `p1` on the planet Earth, calculated
* by the spherical law of cosines (https://en.wikipedia.org/wiki/Great-circle_distance#Formulas).
* @param p1 the coordinates of the first point
* @return a function that given a point `p2` returns the distance in kilometers to the point `p1`.
*/
def distanceFrom(p1: Coordinates): Coordinates => Double = {
val lat1 = toRadians(p1._1)
val sinLat1 = sin(lat1)
val cosLat1 = cos(lat1)
p2 => {
val deltaLong = toRadians(abs(p1._2 - p2._2))
val lat2 = toRadians(p2._1)
val c = acos((sinLat1 * sin(lat2)) + (cosLat1 * cos(lat2) * cos(deltaLong)))
EARTH_RADIUS * c
}
}
}