def test_empty_value_for_cog(self):
"""
this sentence doesn't appear to have a value for course over ground
the binary module should raise a NoBinaryData exception
"""
testsentence = '!AIVDM,1,1,,A,3O>soN5MUNBoMdUdlh,0*64'
nmeatracker = nmea.NMEAtracker()
testdata = nmeatracker.process_sentence(testsentence)
testbinarystr = binary.ais_sentence_payload_binary(testdata)
with self.assertRaises(binary.NoBinaryData):
binary.decode_sixbit_integer(testbinarystr[116:128]) / 10
def __init__(self, msgbinary):
self.msgbinary = msgbinary
self.msgtype = binary.decode_sixbit_integer(msgbinary[0:6])
self.repeatcount = binary.decode_sixbit_integer(msgbinary[6:8])
self.mmsi = str(
format(binary.decode_sixbit_integer(msgbinary[8:38]), '09d'))
try:
self.description = MSGDESCRIPTIONS[self.msgtype]
except KeyError:
self.description = 'Unknown'
self.rxtime = 'N/A'
def process_message(self, data):
"""
determine what type of AIS message it is
Args:
data(str): full message payload from 1 or more NMEA sentences
Raises:
InvalidMMSI: if the mmsi = 000000000
Returns:
msgobj(messages.aismessage.AISMessage): the ais message type object
"""
msgbinary = binary.ais_sentence_payload_binary(data)
msgtype = binary.decode_sixbit_integer(msgbinary[0:6])
if msgtype in (4, 11):
msgobj = allmessages.MSGTYPES[msgtype](msgbinary)
if msgobj.mmsi == '000000000':
raise InvalidMMSI('Invalid MMSI - 000000000')
if msgobj.mmsi not in self.stations:
self.stations[msgobj.mmsi] = AISStation(msgobj.mmsi)
if self.stations[msgobj.mmsi].stnclass == 'Unknown':
self.stations[msgobj.mmsi].determine_station_class(msgobj)
msgobj.rxtime = msgobj.timestamp
self.stations[msgobj.mmsi].find_position_information(msgobj)
self.messagesprocessed += 1
self.messages[allmessages.MSGDESCRIPTIONS[msgtype]] += 1
def decode_turn_rate(rawvalue):
"""
decode the turn rate value to something meaningful
Args:
rawvalue(str): turn rate encoded as binary string
Returns:
turnvalue(str): actual turn rate of the vessel
"""
decodedturnrate = binary.decode_sixbit_integer(rawvalue)
decodedvalues = {
0: 'not turning', 128: 'no turn rate available',
127: ('turning right at more than 10 degrees per minute'
' - NO TURN INDICATOR'),
129: ('turning left at more than -10 degrees per minute'
' - NO TURN INDICATOR')}
if decodedturnrate in decodedvalues:
turnvalue = decodedvalues[decodedturnrate]
else:
twos = binary.decode_twos_complement(rawvalue)
rot = (twos / 4.733) ** 2
if rawvalue[0] == '1':
rot = rot * -1
direction = 'left'
else:
direction = 'right'
turnvalue = 'turning {} at {} degrees per minute'.format(
direction, round(rot, 1))
return turnvalue
def process_message(self, data, timestamp=None):
"""
determine what type of AIS message it is
Note:
the timestamp can be given as an argument for each message to be
processed or timings can be approximated from the last type 4/11
base station report timestamp received. for the latter option it is
preferred that you have a nearby base station transmitting the
correct time on a regular interval
Args:
data(str): full message payload from 1 or more NMEA sentences
timestamp(str): time this message was recieved, if provided this
will take precedence over timings received from AIS
base stations
Raises:
UnknownMessageType: if the message type is not in the
allmessages.MSGTYPES dict
InvalidMMSI: if the mmsi = 000000000
Returns:
msgobj(messages.aismessage.AISMessage): the ais message type object
"""
msgbinary = binary.ais_sentence_payload_binary(data)
msgtype = binary.decode_sixbit_integer(msgbinary[0:6])
if msgtype in allmessages.MSGTYPES.keys():
msgobj = allmessages.MSGTYPES[msgtype](msgbinary)
else:
raise UnknownMessageType(
'Unknown message type {} - {}'.format(msgtype, data))
if msgobj.mmsi == '000000000':
raise InvalidMMSI('Invalid MMSI - 000000000')
if msgobj.mmsi not in self.stations:
self.stations[msgobj.mmsi] = AISStation(msgobj.mmsi)
if self.stations[msgobj.mmsi].stnclass == 'Unknown':
self.stations[msgobj.mmsi].determine_station_class(msgobj)
if (self.stations[msgobj.mmsi].stntype == 'Unknown' or
self.stations[msgobj.mmsi].name == ''):
self.stations[msgobj.mmsi].find_station_name_and_type(msgobj)
if timestamp:
if timestamp not in self.timings:
self.timings.append(timestamp)
else:
if msgtype in (4, 11) and msgobj.mmsi in self.timingsource:
if (msgobj.timestamp != TIMEUNAVAILABLE and
msgobj.timestamp not in self.timings and
kml.DATETIMEREGEX.match(msgobj.timestamp)):
self.timings.append(msgobj.timestamp + ' (estimated)')
try:
timestamp = self.timings[len(self.timings) - 1]
except IndexError:
timestamp = 'N/A'
msgobj.rxtime = timestamp
self.stations[msgobj.mmsi].find_position_information(msgobj)
self.messagesprocessed += 1
self.messages[allmessages.MSGDESCRIPTIONS[msgtype]] += 1
return msgobj
def test_sixbit_integer_decoding(self):
"""
tests converting from binary into integer
"""
binstr = '000001100'
expected = 12
decoded = binary.decode_sixbit_integer(binstr[2:9])
self.assertEqual(expected, decoded)
def decode_sixbit_integer(binarystr):
"""
a wrapper for binary.decode_sixbit_intger
adds exception handling
Note:
if we get a no binary data exception simply return a 0
"""
try:
returnval = binary.decode_sixbit_integer(binarystr)
except binary.NoBinaryData:
returnval = 0
return returnval