to_degrees.rb

class String
  # Converts degrees, minutes and seconds to decimal degrees
  #
  # "52°12′17.0″N".to_degrees # => 52.2047222222222
  # "27 28 05S".to_degrees    # => -27.4680555555556
  # "Invalid".to_degrees      # => 0.0
  #
  # Returns Float
  def to_degrees
    self =~ /^(\d+)[^\d]+(\d+)[^\d]+([\d\.]+)[^NESW]*([NESW])/i
    deg = $1.to_f + ($2.to_f / 60) + ($3.to_f / 3600)
    $4 =~ /[SW]/i ? -deg : +deg
  end
end

puts "52°12′17.0″N".to_degrees
puts "27 28 05S".to_degrees