Convert latitude/longitude pair with radius in meters to 16 sided polygon useful in GIS. Useful for converting a Google maps drawing manager circle into a polygon for storage in a GIS system. Implemented as a class method.

circle_path

def self.circle_path(center, radius, complete_path = false)
  # For increased accuracy, if your data is in a localized area, add the elevation in meters to r_e below:
  r_e = 6378137.0
  @@d2r ||= Math::PI/180
  @@multipliers ||= begin
    segments = 16
    dRad = 2*Math::PI/segments
    (segments + (complete_path ? 1 : 0)).times.map do |i|
      rads = dRad*i
      y = Math.sin(rads)
      x = Math.cos(rads)
      [y.abs < 0.01 ? 0.0 : y, x.abs < 0.01 ? 0.0 : x]
    end
  end
  centerLat = center.first
  centerLng = center.last
  dLat = radius/(r_e*@@d2r)
  dLng = radius/(r_e*Math.cos(@@d2r*centerLat)*@@d2r)
  @@multipliers.map {|m| [centerLat + m[0]*dLat, centerLng + m[1]*dLng]}
end