ruby - midpoint calculation

midpoint.rb

def midpoint(points)
    return [] if points.blank?

    coords = points.map {|p| new(*p).to_radians if p.present?}.compact

    # convert to Cartesian coordinates
    x = []
    y = []
    z = []
    coords.each do |p|
      x << Math.cos(p[0]) * Math.cos(p[1])
      y << Math.cos(p[0]) * Math.sin(p[1])
      z << Math.sin(p[0])
    end

    # compute average coordinate values
    xa, ya, za = [x, y, z].map do |c|
      c.inject(0) {|acc, i| acc + i} / c.size.to_f
    end

    # convert back to latitude/longitude
    lon = Math.atan2(ya, xa)
    hyp = Math.sqrt(xa ** 2 + ya ** 2)
    lat = Math.atan2(za, hyp)

    new(lat, lon).to_degrees
end