Any help with getting NTRIP corrected data inside simple .py script

[ivicajan]

Dear all,
I am starting my project using Ublox ZED F9P at the /dev/ttyACM0 (and NEO-D9S but not used) and got partly stuck so hoping to get some help/guidance. Thanks in advance!

The idea is to use raspberry pi + Ublox ZED F9P (rapi will have wifi connection or usb tethering via phone and have internet access) so would like to have functionality:

1. I can get NTRIP correction via my NTRIP server (tested that part and is working - using rtcm_ntrip_client.py) with some time step of say every 10s (not needed more frequent) .. this should be easy using some already provided examples
2. Incorporate the RTCM3 correction inside ZED F9P (something like send_gnss?)
3. Save high precision location, time, fix, hAcc etc inside the logfile (this is for testing to make sure it is working OK)
4. Final step is to broadcast GPS data via local sever on some high port i.e. 50012 in the NEMA0183 stream so I can connect my navigation app (OpenCPN) to use it.

Is it possible to have all that running inside Python script ?
Tried to figure Threaded approach but a bit struggling with running in daemon mode or piping via buffered stack and interrupting / locking each etc. Some simple sketch or example would mean a lot!

Regards,
Ivica

[semuadmin]

Hi @ivicajan,

So the simple answer is - yes, it's perfectly possible to do all that within a Python Script, though it wouldn't be 'simple'. I'm not in a position to help you write your application code, but I'm happy to provide guidance on the use of pygnssutils. You're on the right track with the examples you've cited.

It would be helpeful to understand your overall objectives here - what is it you're ultimately looking to achieve?

FYI The gnssstreamer CLI utility will do much of what you ask from the command line, e.g. the following command will:

• stream inbound GNSS data from receiver at serial port /dev/ttyACM1
• get RTCM3 corrections from NTRIP caster rtk2go.com and send these to the receiver (NB NTRIP typically outputs RTCM corrections at a rate of 1 Hz and you need to send ALL these corrections to the receiver - sending them only every 10 seconds will produce very poor results)
• broadcast the binary GNSS data on IP address <<host_ip_address>> port 50012 - your client (OpenCPN?) will need to be capable of parsing this GNSS data via a TCP socket

gnssstreamer --port /dev/ttyACM1 --cliinput 1 --input "http://rtk2go.com:2101/MYMOUNTPOINT" --rtkuser myusername@mydomain.com --rtkpassword mypassword --rtkggaint 10 --clioutput 3 --output 192.168.0.27:50012 --format 2 --verbosity 2

If you want to run this as a script rather than a CLI, have a look at the API documentation for GNSSStreamer in the first instance and get back to me with any further queries. Essentially you'd need to override the default inputhandler() and outputhandler() functions.

[ivicajan]

Hi Steve,
Thanks a lot for a swift answer.

I had a look at the pygnssutils and made initial test on the gnssstreamer to see if NTRIP is working.
However, was not aware it can broadcast standard NMEA0183 format I used example from their site with pipe to lambda function. Options you suggested "-clioutput 3 --format 2" possibly did the trick!

Possibly there is no need for Python, I can pack all that into shell script and even capture packets from TCP using netcat and store result into separate logfile.

Just from the curiosity, the NEO-D9S chip could be able to receive L1/L2 satellite corrections that are not pointperfect only? In other words possibly free data from the GALILEO HAS (https://www.gsc-europa.eu/galileo/services/galileo-high-accuracy-service-has) ?

Thanks!
Ivica

Thanks once again!
Regards
Ivica

[semuadmin]

Just from the curiosity, the NEO-D9S chip could be able to receive L1/L2 satellite corrections that are not pointperfect only? In other words possibly free data from the GALILEO HAS (https://www.gsc-europa.eu/galileo/services/galileo-high-accuracy-service-has) ?

AFAIK the NEO D9S should - as you infer - be capable of functioning as a generic L-Band modem, but unless I'm mistaken Galileo HAS is only available on E6 (L6), and I'm not sure the RF module in the D9S can handle that - this is probably a question for the u-blox forum. You may be better off with the newer ZED-X20P.