# Generate the checksum for some data
# (Checksum is all the data XOR'd, then turned into hex)
def generate_checksum(data):
	csum = 0
	for c in data:
		csum = csum ^ ord(c)
	hex_csum = "%02x" % csum
	return hex_csum.upper()

# Format a NMEA timestamp into something friendly
def format_time(time):
	hh = time[0:2]
	mm = time[2:4]
	ss = time[4:]
	return "%s:%s:%s UTC" % (hh,mm,ss)

# Format a NMEA date into something friendly
def format_date(date):
	months = ('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec')
	dd = date[0:2]
	mm = date[2:4]
	yy = date[4:6]
	yyyy = int(yy) + 2000
	return "%s %s %d" % (dd, months[(int(mm)-1)], yyyy)

#############################################################################
    
# Get the location from a GGA sentence
def get_gga_location(data):
	'''$GPGGA,042327,3722.1926,N,12656.7660,E,1,03,04.5,00000.0,M,018.1,M,,*41'''
	d = data.split(',')
	ret = {}
	ret['type'] = 'GGA'
	ret['lat'] = getKML_lat("%s%s" % (d[1],d[2]))
	ret['long'] = getKML_long("%s%s" % (d[3],d[4]))
	ret['time'] = format_time(d[0])
	ret['alti'] = '%s%s'%(d[8],d[9])
	return ret

# Get the location from a GLL sentence
def get_gll_location(data):
	d = data.split(',')
	ret = {}
	ret['type'] = 'GLL'
	ret['lat'] = getKML_lat("%s%s" % (d[0],d[1]))
	ret['long'] = getKML_long("%s%s" % (d[2],d[3]))
	ret['time'] = format_time(d[4])
	return ret

# Get the location from a RMC sentence
def get_rmc_location(data):
	'''$GPRMC,042327,A,3722.1926,N,12656.7660,E,000.0,019.3,071206,,,A*70'''
	d = data.split(',')
	ret = {}
	ret['type'] = 'RMC'
	ret['lat'] = getKML_lat("%s%s" % (d[2],d[3]))
	ret['long'] = getKML_long("%s%s" % (d[4],d[5]))
	ret['time'] = format_time(d[0])
	ret['date'] = format_date(d[8])
	return ret

#############################################################################

def getKML_lat(s):
    '3721.1122N'
    h = s[:2]
    b = s[2:-1]
    p = s[-1]
    d_h = eval(h)
    d_b = eval(b)

    d = d_h + (d_b/60)
    if p == 'N':
        return '%.8f'%d
    else:
        return '-%.8f'%d

def getKML_long(s):
    #print 'getKML_long',nmea_long
    '12655.5694E'
    h = s[:3]
    b = s[3:-1]
    p = s[-1]
    d_h = eval(h)
    d_b = eval(b)
    d = d_h + (d_b/60)
    if p == 'E':
        return '%.8f'%d
    else:
        return '-%.8f'%d

def getLocation(nmeaLine):
        data = nmeaLine.strip()
        if not data:
            return ''#continue
        
	# Ensure it starts with $GP
	if not data[0:3] == '$GP':
	    return ''#continue

	# If it has a checksum, ensure that's correct
	# (Checksum follows *, and is XOR of everything from
	#  the $ to the *, exclusive)
	if data[-3] == '*':
	    exp_checksum = generate_checksum(data[1:-3])
	    if not exp_checksum == data[-2:]:
		print "Invalid checksum %s, expecting %s" % (data[-2:], exp_checksum)
                return ''#continue
		
	    # Strip the checksum
	    data = data[:-3]
	    
        # Grab the parts of the sentence                    
	talker = data[1:3]
	sentence_id = data[3:6]
	sentence_data = data[7:]
        #print l

	location = {}
	if sentence_id == 'GGA':
	    location = get_gga_location(sentence_data)
	elif sentence_id == 'GLL':
	    location = get_gll_location(sentence_data)
	elif sentence_id == 'RMC':
	    location = get_rmc_location(sentence_data)
	else:
            return ''#continue
	return location

#############################################################################

if __name__ == '__main__':

    dataFile = 'Data\\WG20061207132002.log'
    
    for data in open(dataFile):
        data = data.strip()
        if not data: continue
        location = getLocation(data)
        if location:
            print '%s,%s,%s'%(location['type'],location['lat'],location['long'])