NMEA Parser

A library used to decode NMEA data streams from GNSS receivers. Capable of parsing a text file containing NMEA data or reading from a serial port real time.

This library is currently in Beta and is subject to change any time.

Dependencies

PySerial is the only dependency. See requirements.txt.

Usage

See www.bek.sh/nmea-parser for a full manual.

Examples

Opening and Reading a Serial Port

It is highly sugested that you use all input streams within a context manager (with statement) as shown below.

from nmea import input_stream

stream = input_stream.GenericInputStream.open_stream('/dev/ttyACM0', 9600)

print(stream)

with stream:
    print(stream.get_line())

If you must use an input stream without a context manager, make sure that the ensure_closed() function is called prior to exit:

from nmea import input_stream

stream = input_stream.GenericInputStream.open_stream('/dev/ttyACM0', 9600)

print(stream)
print(stream.get_line())
stream.ensure_closed()      # You must not forget to manually close the stream.

Using a context manager ensures that the port is always closed should your program halt unexpectedly.

GenericInputStream.open_stream() also accepts all keyword arguments that are accepted by serial.Serial() in PySerial.

Opening and Reading a NMEA Dump file

Text files containing NMEA streams may also be used with this library. Just point the open_stream() function at the desired file:

from nmea import input_stream, data_frame

stream = input_stream.GenericInputStream.open_stream('sample-data/sample1.txt')

with stream:
    new_frame = data_frame.DataFrame.get_next_frame(stream)

    print("Current GPS time:", new_frame.gps_time)
    print("Current Latitude:", new_frame.latitude)
    print("Current Longitude:", new_frame.longitude)
    print("Current Speed:", new_frame.velocity)
    print("Current heading:", new_frame.track)

Getting Position Data and Logging to a Database

The DataFrame object contains properties that allow you to access your current position, movement, and information on all satellites used to calculate your fix. The logging module allows you to record these objects in an SQLite database.

from nmea import input_stream, data_frame, database_wrapper

stream = input_stream.GenericInputStream.open_stream('/dev/ttyACM0', 9600)

db = database_wrapper.SQLiteConnection.from_path('./example.sqlite')

print(stream)

with stream:
    while True:
        new_frame = data_frame.DataFrame.get_next_frame(stream)

        print("Current GPS time:", new_frame.gps_time)
        print("Current Latitude:", new_frame.latitude)
        print("Current Longitude:", new_frame.longitude)
        print("Current Speed:", new_frame.velocity)
        print("Current heading:", new_frame.track)
        print("Number of Satellites above:", new_frame.nsats)
        print("Individual Observations:")
        for obs in new_frame.sv_observations:
            print('\tPRN:', obs.prn)
            print('\t\tSignal to Noise:', obs.snr)
            print('\t\tAzimuth:', obs.azimuth)
            print('\t\tElevation:', obs.elevation)

        db.insert_dataframe(new_frame)