GPS Class taken from original example https://github.com/DexterInd/GrovePi/blob/master/Software/Python/grove_gps.py

grove_gps.py

#!/usr/bin/env python
#
# GrovePi Example for using the Grove GPS Module http://www.seeedstudio.com/depot/Grove-GPS-p-959.html?cPath=25_130
#
# The GrovePi connects the Raspberry Pi and Grove sensors.  You can learn more about GrovePi here:  http://www.dexterindustries.com/GrovePi
#
# Have a question about this example?  Ask on the forums here:  http://www.dexterindustries.com/forum/?forum=grovepi
#
# LICENSE: 
# These files have been made available online through a [Creative Commons Attribution-ShareAlike 3.0](http://creativecommons.org/licenses/by-sa/3.0/) license.
#                                                           
# History
# ------------------------------------------------
# Author     Date      		Comments
# Karan      21 Aug 14 		Initial Authoring

import serial, time
import smbus
import math
import RPi.GPIO as GPIO
import struct
import sys

ser = serial.Serial('/dev/ttyAMA0',  9600, timeout = 0)	#Open the serial port at 9600 baud
ser.flush()

class GPS:
	#The GPS module used is a Grove GPS module http://www.seeedstudio.com/depot/Grove-GPS-p-959.html
	inp=[]
	# Refer to SIM28 NMEA spec file http://www.seeedstudio.com/wiki/images/a/a0/SIM28_DATA_File.zip
	GGA=[]

	#Read data from the GPS
	def read(self):	
		while True:
			GPS.inp=ser.readline()
			if GPS.inp[:6] =='$GPGGA': # GGA data , packet 1, has all the data we need
				break
			time.sleep(0.1)     #without the cmd program will crach
		try:
			ind=GPS.inp.index('$GPGGA',5,len(GPS.inp))	#Sometimes multiple GPS data packets come into the stream. Take the data only after the last '$GPGGA' is seen
			GPS.inp=GPS.inp[ind:]
		except ValueError:
			print ""
		GPS.GGA=GPS.inp.split(",")	#Split the stream into individual parts
		return [GPS.GGA]
		
	#Split the data into individual elements
	def vals(self):
		time=GPS.GGA[1]
		lat=GPS.GGA[2]
		lat_ns=GPS.GGA[3]
		long=GPS.GGA[4]
		long_ew=GPS.GGA[5]
		fix=GPS.GGA[6]
		sats=GPS.GGA[7]
		alt=GPS.GGA[9]
		return [time,fix,sats,alt,lat,lat_ns,long,long_ew]