Acquiring postion data with a GPS receiver

gpsserial.py

#!/usr/bin/python

import serial

class Position(object) :
  def __init__(self) :
    self.latitude = 0.0
    self.longitude = 0.0
    self.altitude = 0.0
    self.courseOverGround = 0.0
    self.speedOverGround = 0.0
    self.HDOP = 0.0
    self.satellites = 0
    self.dateTime = ""
 
  def update_with_RMC(self, sent) :
    data= sent.split(",")

    latitude=data[3]
    latd=latitude[0:2]
    latm=latitude[2:]
    lat_dir = 1
    if data[4] == "S" :
      lat_dir = -1
    self.latitude = (int(latd) + float(latm) / 60) * lat_dir

    longitude=data[5]
    longd=longitude[0:3]
    longm=longitude[3:]
    long_dir = 1
    if data[6] == "W" :
      long_dir = -1
    self.longitude = (int(longd) + float(longm) / 60) * long_dir

    time =data[1]
    h = time[0:2]
    m = time[2:4]
    s = time[4:len(time)]
    self.time = ":".join((h,m,s))
    self.seconds = (int(h)*60 + int(m) )* 60 + float(s)
   
    date= data[9]
    day = date[0:2]
    month = date[2:4]
    year = date[4:6]
    self.date = "-".join(("20"+year,month,day))
    self.dateTime = self.date+"T"+self.time
    self.speedOverGround = data[7]
    self.courseOverGround = data[8]

  def update_with_GGA(self, sent) :
    data = sent.split(",")
    self.altitude = data[9]
    self.satellites = data[7]
    self.HDOP = data[8]
 
  def __str__(self) :
    return " ".join((self.dateTime,str(round(self.latitude,5)),str(round(self.longitude,5)),self.altitude,"["+self.satellites+":"+ self.HDOP+"]"))

 
s = serial.Serial("/dev/ttyUSB0",4800)
position = Position()
while True:
   nmea = s.readline()
   if nmea.startswith("$GPRMC") :
      position.update_with_RMC(nmea)
      print position
     
   elif nmea.startswith("$GPGGA") :
      position.update_with_GGA(nmea)