RTCM3 Protocol Parser
Reason this release was yanked:
obsolete
Project description
pyrtcm
Current Status | Installation | Reading | Parsing | Generating | Serializing | Examples | Extensibility | Graphical Client | Author & License
pyrtcm
is an original Python 3 parser for the RTCM3 © GPS/GNSS protocol. RTCM3 is a proprietary GPS/GNSS differential correction or DGPS protocol published by the Radio Technical Commission for Maritime Services.
RTCM STANDARD 10403.n DIFFERENTIAL GNSS (GLOBAL NAVIGATION SATELLITE SYSTEMS) SERVICES – VERSION 3.
The pyrtcm
homepage is located at https://github.com/semuconsulting/pyrtcm.
This is an independent project and we have no affiliation whatsoever with the Radio Technical Commission for Maritime Services.
FYI There are companion libraries which handle standard NMEA 0183 © and UBX © (u-blox) GNSS/GPS messages:
Current Status
Currently in development. Refer to the RTCM_PAYLOADS_GET
dictionary in rtcmtypes_get.py
for a list of message types currently implemented (but not necessarily tested). Additional message types can be readily added - see Extensibility).
Sphinx API Documentation in HTML format is available at https://www.semuconsulting.com/pyrtcm.
Contributions welcome - please refer to CONTRIBUTING.MD.
Bug reports and Feature requests - please use the templates provided.
Installation
pyrtcm
is compatible with Python 3.6+ and has no third-party library dependencies.
In the following, python
& pip
refer to the Python 3 executables. You may need to type
python3
or pip3
, depending on your particular environment.
The recommended way to install the latest version of pyrtcm
is with
pip:
python -m pip install --upgrade pyrtcm
Local installation is also available, provided you have the Python packages setuptools
and wheel
installed:
git clone https://github.com/semuconsulting/pyrtcm.git
cd pyrtcm
python setup.py sdist bdist_wheel
python -m pip install dist/pyrtcm-0.1.3.tar.gz --user --force_reinstall
Reading (Streaming)
class pyrtcm.rtcmreader.RTCMReader(stream, **kwargs)
You can create a RTCMReader
object by calling the constructor with an active stream object.
The stream object can be any data stream which supports a read(n) -> bytes
method (e.g. File or Serial, with
or without a buffer wrapper).
Individual RTCM messages can then be read using the RTCMReader.read()
function, which returns both the raw binary data (as bytes) and the parsed data (as a RTCMMessage
, via the parse()
method). The function is thread-safe in so far as the incoming data stream object is thread-safe. RTCMReader
also implements an iterator.
Example - Serial input:
>>> from serial import Serial
>>> from pyrtcm import RTCMReader
>>> stream = Serial('/dev/tty.usbmodem14101', 9600, timeout=3)
>>> rtr = RTCMReader(stream)
>>> (raw_data, parsed_data) = rtr.read()
>>> print(parsed_data)
Example - File input (using iterator).
>>> from pyrtcm import RTCMReader
>>> stream = open('rtcmdata.log', 'rb')
>>> rtr = RTCMReader(stream)
>>> for (raw_data, parsed_data) in rtr: print(parsed_data)
...
Parsing
You can parse individual RTCM messages using the static RTCMReader.parse(data)
function, which takes a bytes array containing a binary RTCM message and returns a RTCMMessage
object.
NB: Once instantiated, an RTCMMessage
object is immutable.
Example:
>>> from pyrtcm import RTCMReader
>>> msg = RTCMReader.parse(b"\xd3\x00\x13>\xd0\x00\x03\x8aX\xd9I<\x87/4\x10\x9d\x07\xd6\xafH Z\xd7\xf7")
>>> print(msg)
<RTCM(1005, DF002=1005, DF003=0, DF021=0, DF022=1, DF023=1, DF024=1, DF141=0, DF025=44440308028, DF142=1, DF001_1=0, DF026=30856712349, DF364=0, DF027=33666582560)>
The RTCMMessage
object exposes different public attributes depending on its message type or 'identity'. Attributes are defined as data fields ("DF002", "DF003", etc.) e.g. the 1005
message contains the following data fields:
>>> print(msg)
<RTCM(1005, DF002=1005, DF003=0, DF021=0, DF022=1, DF023=1, DF024=1, DF141=0, DF025=44440308028, DF142=1, DF001_1=0, DF026=30856712349, DF364=0, DF027=33666582560)>
>>> msg.identity
'1005'
>>> msg.DF024
1
Helper methods are available to interpret the individual datafields:
>>> from pyrtcm import RTCM_DATA_FIELDS, datasiz, datares, datadesc
>>> dfname = "DF012"
>>> RTCM_DATA_FIELDS[dfname]
(INT20, 0.0005, "GPS L1 PhaseRange - L1 Pseudorange")
>>> datasiz(dfname) # size in bits
20
>>> datares(dfname) # resolution
0.0005
>>> datadesc(dfname) # description
'GPS L1 PhaseRange - L1 Pseudorange'
Attributes within repeating groups are parsed with a two-digit suffix ("DF030_01", "DF030_02", etc.). The payload
attribute always contains the raw payload as bytes.
Generating
class pyrtcm.rtcmmessage.RTCMMessage(payload, **kwargs)
You can create an RTCMMessage
object by calling the constructor with the following parameters:
- payload as bytes
Example:
>>> from pyrtcm import RTCMMessage
>>> msg = RTCMMessage(b">\xd0\x00\x03\x8aX\xd9I<\x87/4\x10\x9d\x07\xd6\xafH ")
>>> print(msg)
<RTCM(1005, DF002=1005, DF003=0, DF021=0, DF022=1, DF023=1, DF024=1, DF141=0, DF025=44440308028, DF142=1, DF001_1=0, DF026=30856712349, DF364=0, DF027=33666582560)>
Serializing
The RTCMMessage
class implements a serialize()
method to convert a RTCMMessage
object to a bytes array suitable for writing to an output stream.
e.g. to create and send a 1005
message type:
>>> from serial import Serial
>>> serialOut = Serial('COM7', 38400, timeout=5)
>>> from pyrtcm import RTCMMessage
>>> msg = RTCMMessage(b">\xd0\x00\x03\x8aX\xd9I<\x87/4\x10\x9d\x07\xd6\xafH ")
>>> print(msg)
<RTCM(1005, DF002=1005, DF003=0, DF021=0, DF022=1, DF023=1, DF024=1, DF141=0, DF025=44440308028, DF142=1, DF001_1=0, DF026=30856712349, DF364=0, DF027=33666582560)>
>>> output = msg.serialize()
>>> output
b'\xd3\x00\x13>\xd0\x00\x03\x8aX\xd9I<\x87/4\x10\x9d\x07\xd6\xafH Z\xd7\xf7'
>>> serialOut.write(output)
Examples
The following examples are available in the /examples folder:
rtcmfile.py
- illustrates how to stream RTCM data from binary log file.rtcmserial.py
- illustrates how to stream RTCM data from serial/UART port.rtcmbuild.py
- illustrates how to construct RTCM payload from constituent datafields.
Extensibility
The RTCM protocol is principally defined in the modules rtcmtypes_core.py
and rtcmtypes_get.py
as a series of dictionaries. RTCM uses a series of pre-defined data fields ("DF002", DF003" etc.), each of which has a designated data type (UINT32, etc.). Message payload definitions must conform to the following rules:
1. datafield names must be unique within each message class
2. datafield types must be one of the valid data fields ("DF026", "DF059", etc.)
3. repeating or bitfield groups must be defined as a tuple ('numr', {dict}), where:
'numr' is either:
a. an integer representing a fixed number of repeats e.g. 32
b. a string representing the name of a preceding attribute containing the number of repeats e.g. 'DF029'
{dict} is the nested dictionary of repeating items or bitfield group
Repeating attribute names are parsed with a two-digit suffix ("DF030_01", "DF030_02", etc.). Nested repeating groups are supported.
Graphical Client
A python/tkinter graphical GPS client which supports NMEA, UBX and RTCM protocols is available at:
https://github.com/semuconsulting/PyGPSClient
Author & License Information
pyrtcm
is maintained entirely by volunteers. If you find it useful, a small donation would be greatly appreciated!
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