playback VDR from recorded file

[skipperearly]

I don't want to be difficult but it appears I fail to explain clearly.
Per definition the only NMEA sentences which carry a SOG are xxRMC, xxVBM, xxVHW and xxVTG.
I know that VDR is not generating any NMEA sentences but only record them or play them back.
If you check my log file track_13052018 https://www.dropbox.com/s/rz50zm8e63...y.rar.doc?dl=0
you see in my setup only xxRMC sentences are logged.

I now playback this file with max speed in VDR with calculate SOG option NOT selected and get realistic SOG values between 5 and 7 knt.
Doing the same but with calculate SOG option ticked I get SOG 60 - 70 knts. So obviously the algorithm is taking the computer time to calculate SOG from the coordinates. It should be GPS TIME.

Please check this with my log file and if this is different then there is something fishy in my configuration.

I conclude that I can live with current behavior but it is not correct from an users point of view.
I have made a remark in the manual to alert users on this particularity.

... and now I rest my case

[nohal]

Originally Posted by skipperearly

I don't want to be difficult but it appears I fail to explain clearly.
Per definition the only NMEA sentences which carry a SOG are xxRMC, xxVBM, xxVHW and xxVTG.
I know that VDR is not generating any NMEA sentences but only record them or play them back.
If you check my log file track_13052018 https://www.dropbox.com/s/rz50zm8e63...y.rar.doc?dl=0
you see in my setup only xxRMC sentences are logged.

I now playback this file with max speed in VDR with calculate SOG option NOT selected and get realistic SOG values between 5 and 7 knt.
Doing the same but with calculate SOG option ticked I get SOG 60 - 70 knts. So obviously the algorithm is taking the computer time to calculate SOG from the coordinates. It should be GPS TIME.

Please check this with my log file and if this is different then there is something fishy in my configuration.

I conclude that I can live with current behavior but it is not correct from an users point of view.
I have made a remark in the manual to alert users on this particularity.

... and now I rest my case

If you were actually reading my posts, the calculated SOG/COG feature was implemented to address a specific real world issue where GPS TIME was NOT AVAILABLE.

[rgleason]

New FAQ under the VDR_pi manual

Why is my SOG way off and showing 60-70 knots in the Dashboard, when I playback a file?

[Schnapsy]

In the VDR faq, it is clear that :

"(...) When recording, the VDR plugin includes all NMEA data available on the internal bus in OpenCPN. Even data not recognized or used by OpenCPN will be recorded. Everything (almost) in the ToolBar → Connections → NMEA debug window will be included.(...)"

This is my case: OCN does not natively recognize my DBT sentence, I have to add it in the connections.
This is possible with a valid COM port, but how to do it with VDR ?

There is - apparently - no possibility to add the NMEA sentences that are read by VDR but not taken into account by OpenCPN.

Incidentally, it would be very good if we could one for all indicate any NMEA sentence to OCN and then, even if we change the COM port, he knows recognize them ... Wishful ...

[rgleason]

Can't you use nmeaconverter_pi to have it recognized?


This is my case: OCN does not natively recognize my DBT sentence, I have to add it in the connections.

This is possible with a valid COM port, but how to do it with VDR ?

There is - apparently - no possibility to add the NMEA sentences that are read by VDR but not taken into account by OpenCPN.