Realtime monitoring and logs intermittent does not show speed or speed is incorrect

[Brazen Article]

In the realtime monitoring and in recorded logs I am seeing zero boat speed most of the time. Sometimes the boat speed will show up but it is incorrect, almost like it is adding wind speed and boat speed.
The log from February 1, 2024 shows this....
Any ideas or suggestions to get it back to normal?

Brazen Article
Time 2/1/2024, 12:02:16 PM
Boat Speed 0 knots
Wind Speed 5.7 knots
Latitude 25.388367
Longitude -80.2637928

Brazen Article
Time 2/1/2024, 12:07:19 PM
Boat Speed 11.1 knots
Wind Speed 6 knots
Latitude 25.3823747
Longitude -80.2693225

[admin]

Thank you for the note. Looking at logs, I see the max boat speed to be recorded as non-zero for all of the recent logs (verified 25 of them).

Is this for captured logs or the monitoring page? Could you send the specific log id so we can look in more detail?

Separately, what does Signal K show for wind speed in the Data Browser?

[Brazen Article]

One of the logs is #14804 From Coconut Grove Sailing Club to Tarpon Basin North (referenced in note above).
When I click on the log view it shows zero boat speed at some points, incorrect speed at others. Wind speed seems okay.
Log #15157 is a short trip from fuel dock to mooring, it shows wind speed but no boat speed.

When on the move with realtime monitoring the boat speed has been zero. Not sure when that started, my recollection is it worked fine some weeks ago.

Stupid question here....how do I download a specific trip as a csv so I can see all the data points? I'm pretty sure I've done that in the past but now I'm just downloading the log summary page

SignalK windspeed seems correct, it is apparent wind, not true wind.
environment.wind.speedApparent

[admin]

This is a bit of an odd case indeed. Looking at all the data points for log 15157, I see 10 of them 14 not having boat speeds but the remaining 4 do. For 14804 69 out of 100 are zeroes. So it is not everything is zero, but there are quite a few of zero boat speed readings. This is pretty unusual.

One thing to probe is the frequency of boat speed readings coming from your instruments to Signal K. For one reason another, a speed reading seems to be not sent in between data point collections. Can you go to Data Browser in Signal K and watch the value of navigation.speedOverGround ? How often does it get refreshed? (the time field should indicate that) Relatedly, what kind of instrument (or instruments) is emitting the speedOverGround.

To your question on exports, you can use https://saillogger.com/timelapse/export/ link to export one more log data points as GPX.

[Brazen Article]

Speed over ground is on the N2K network, it appears multiple times in data browser, pointing to different N2K PGNs. I'm not sure how to edit or eliminate a source, perhaps another option is to map one of the sources as a priority?
I appreciate you taking the time to help me figure this out.

[admin]

Few thoughts:

• Speed over Ground reading seem to diverge a bit. There are 4 readings between zero and 0.15 m/s in 0.5 increments (after conversion 0, 0.1, 0.2 and 0.3 knots respectively). They are small numbers so hard to guess what they will show while underway. Do you know which one is the most accurate?

• Do you have GPS source configured for Saillogger plugin configuration on Signal K?

• If not, you could try specifying one of these (the most reliable) as a source? This is explained in Question 14 of the FAQ.

Independently, I can see a way to slightly improve this behavior in the plugin code but that will be compensating for lack of data and not really a solution for more accuracy. Ideal solution is somewhere in the above options.

[Brazen Article]

Thanks - I configured the GPS source and will keep an eye on it when I'm on the move again. I'll also read through the FAQs again, lots of good information in there!