AIVDO synthesizes GPRMC in kplex..? Bug or Feature..?

[Dave Wright]

I am seeing 'synthesized' GPRMC messages out of kplex when AIVDO is present as an input. Nothing in the docs alludes to this, although a report here sometime back looks similar...

I'm running the Raspbian 1.4 build

The synthesized GPRMC message differs from what I see from my gpsd GPRMC source. The time field has an appended ".000" and the magnetic variation field is empty.

This is a problem as the AIS position and the gpsd positions are always differing, and results in OpenCPN jumping the displayed position around. OpenCPN can prioritize between AIVDO and GPRMC, but it cannot discern multiple GPRMC messages.

So, this might be a feature, and I can see its utility in some cases. But, I want to be able to turn it on or off. The present workaround is to ifilter the AIVDO, but then it is unavailable to clients that want it. Failover is not an option either, I want the client to decide whether to use AIVDO or GPRMC, once it appears as an additional (and differing) GPRMC it becomes positional 'noise'.

If this is a feature, please add it to the docs..! Presently it looks like a bug...

So, we could add a switch to enable/disable "AIVDO to GPRMC" , and/or change the talker address to allow further filtering. ECRMC is one of many possibilities...

P.S. I love pretty much everything else about kplex, and appreciate the work, thanks..!

Dave

M/V KittyHawk

KC6UPS

[Dave Wright]

So, some time has passed, and nothing in the way of a confirmation from other users, or reply from the author...

Do any of you have an implementation that is receiving AIVDO messages, and can look and see if this is happening to you as well..?

Again, if AIVDO is present as an input, it appears that kplex is creating a GPRMC message with the position information from AIVDO. 

Appreciate any info regarding whether you see this, and if so, on what build. Thanks.

Dave

M/V KittyHawk

KC6UPS

[Keith Young]

Sincere apologies for the delayed reply.

kplex doesn't synthesise sentences so the GPRMC must be coming from one of your inputs.  if its problematic you can filter out GPRMC sentences, either from the input or in the output to opencpn

[Dave Wright]

Keith,

Welcome home..!

Just now took another look at the 'gozintas' and 'comesouta', and yes I was mistaken. The Garmin AIS-600 does produce GPRMC as well as AIVDO and AIVDM (and also two PGRM status messages).

Was able to ifilter the RMC at the AIS receive, and OpenCPN is able to use the AIVDO as a fallback position with lower priority.

All happy now....

Thanks again for putting in the work on kplex..!

Sent from my iPhone, aboard KittyHawk, Ohio River MM 582

On Aug 14, 2024, at 2:49 PM, Keith Young <strip...@gmail.com> wrote:

Sincere apologies for the delayed reply.

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