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NMEA GPS and Google Map in 23 lines of code

Posted by Sandro Paganotti in Ruby on Rails - comments are closed

Today I’ve found this fantastic example: GPS and Google Map with Python in 42 lines of code obviously the first thing I thought was

how can I do this in Ruby?

• first of all I installed the ruby-serialport gem
• then I located the serial port which map my GPS bluetooth device; this procedure could vary depending on which os your working on; in Os X I had to create a serial port from the bluetooth panel ( first click on the device, then click on the “Edit Serial Ports…” button and configure the serial port as shown in the following snapshot ).

• last I rewrite the code I found in ruby; this is the result :

require 'serialport'

def dmmm2dec(degrees,sw)
  deg= (degrees/100.0).floor #decimal degrees
  frac= ((degrees/100.0)-deg)/0.6 #decimal fraction
  ret = deg+frac #positive return value
  if ((sw=="S") or (sw=="W")):
      ret=ret*(-1) #flip sign if south or west
  end
  return ret
end

sp = SerialPort.new('/dev/tty.holux', 4800,8,1,SerialPort::NONE)

while(line=sp.readline) do
  if line =~ /\$GPGGA/
    tokens = line.split(",")
    lat = dmmm2dec((tokens[2]).to_f,tokens[3]) #[2] is lat in deg+minutes, [3] is {N|S|W|E}
    lng = dmmm2dec((tokens[4]).to_f,tokens[5]) #[4] is long in deg+minutes, [5] is {N|S|W|E}
    puts "http://maps.google.com/maps?ie=UTF8&ll=#{lat},#{lng}" 
    sleep 1
  end
end

Sandro.

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