Coordinates of a point on surface of earth at a distance and bearing from given point

coords_at_dist.rb

# http://www.movable-type.co.uk/scripts/latlong.html
# Destination point given distance and bearing from start point

# Radius of earth
R=6371

# Return the lat2 & lon2 of a point at distance d and
# bearing brng from an initial point wt coords lat1 & lon1
def coords_at_dist lat1, lon1, d, brng
  # lat1 => latitude at initial point
  # lon1 => longitude at initial point
  # brng => bearing towards final point
  # d => distance to final point

  lat1 = deg2rad lat1
  lon1 = deg2rad lon1
  brng = deg2rad brng

  lat2 = Math.asin(Math.sin(lat1)*Math.cos(d/R)+Math.cos(lat1)*Math.sin(d/R)*Math.cos(brng))
  lon2 = lon1 + Math.atan2(Math.sin(brng)*Math.sin(d/R)*Math.cos(lat1), Math.cos(d/R)-Math.sin(lat1)*Math.sin(lat2))

  # formula for normalizing longitude
  # lon2 = (lon2+540)%360-180

  [brk(lat2), brk(lon2)]
end

# Turns angle in radians to [degrees, minutes]
def brk rad
  deg = rad2deg rad
  [deg.to_i, ((deg-deg.to_i)*60).abs]
end

def deg2rad deg
  deg * Math::PI / 180
end

def rad2deg rad
  rad * 180 / Math::PI
end

# res = coords 6.5, 3.4, 120.0, 32.0
# res = coords 0, 20.4, 1800.0, 95.0
res = coords_at_dist 5.6037, 0, 1000.0, -30.0
print res