Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 17-05-2018, 08:36   #1
Registered User

Join Date: Feb 2012
Location: Austria
Posts: 162
playback VDR from recorded file

Have recorded a recent trip and want to playback route now with faster speed.
When doing so the SOG shown in the dashboard becomes meaningless rather than showing the original SOG.

Want to check here if others have same behavior before I raise a bug report.
__________________

skipperearly is offline   Reply With Quote
Old 17-05-2018, 09:41   #2
Registered User
 
rgleason's Avatar

Join Date: Mar 2012
Location: Boston, MA
Boat: 1981 Bristol 32 Sloop
Posts: 11,169
Re: playback VDR from recorded file

Under Dashboard preferences > appearance, what do you have for settings for
Cog damping factor and Speed over Ground damping factor?
__________________

rgleason is online now   Reply With Quote
Old 17-05-2018, 10:06   #3
Registered User

Join Date: Feb 2010
Location: On the go. Not in Prague.
Posts: 4,527
Re: playback VDR from recorded file

Quote:
Originally Posted by skipperearly View Post
Have recorded a recent trip and want to playback route now with faster speed.
When doing so the SOG shown in the dashboard becomes meaningless rather than showing the original SOG.

Want to check here if others have same behavior before I raise a bug report.
You want to fill a bug report for what exactly (= what is "meaningless" in the context of your post)? Remember that when you play the VDR data, you simulate data flow from the actual sensors - while playing at 10x the original speed at which it was recorded, your position changes 10x faster and your resulting SOG is obviously something like 10x higher than it actually was.
nohal is offline   Reply With Quote
Old 17-05-2018, 12:03   #4
Registered User

Join Date: Feb 2012
Location: Austria
Posts: 162
Re: playback VDR from recorded file

@rgleason: SOG damping 40, COG damping 15

@nohal: well maybe the objective of the pi is not as I expected. I was expecting that when I record in VDR all available data are recorded (I noticed even AIS data are recorded - which BTW I find great for proof in case needed !) - so following this logic I had expected the "real" SOG to be recorded. To play the file faster or slower should not make any changes to the SOG - similar to when you fast forward a video you also do not show the actual time but the time of the original video.

.. if the current behavior is as required by design and not a bug but a feature to create virtual SOG's then I propose to raise it as a feature request
skipperearly is offline   Reply With Quote
Old 17-05-2018, 16:13   #5
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 4,368
Images: 4
Re: playback VDR from recorded file

Quote:
Originally Posted by nohal View Post
Remember that when you play the VDR data, you simulate data flow from the actual sensors - while playing at 10x the original speed at which it was recorded, your position changes 10x faster and your resulting SOG is obviously something like 10x higher than it actually was.
Is the VDR playback calculating SOG from the difference in GPS positions and using the realtime computer clock? I don't think it should, rather, it should be using the SOG as given by the GPS RMC sentence or similar data. In this case the displayed SOG should be identical to the original SOG. At least that's now NavMonPc does it.

If somehow the SOG is re-calculated based on the playback speed-up, then wouldn't the wind speed / angle also need to be recalculated? And why would any of this be useful?
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 17-05-2018, 16:19   #6
Registered User

Join Date: Feb 2010
Location: On the go. Not in Prague.
Posts: 4,527
Re: playback VDR from recorded file

Quote:
Originally Posted by Paul Elliott View Post
Is the VDR playback calculating SOG from the difference in GPS positions and using the realtime computer clock? I don't think it should, rather, it should be using the SOG as given by the GPS RMC sentence or similar data. In this case the displayed SOG should be identical to the original SOG. At least that's now NavMonPc does it.

If somehow the SOG is re-calculated based on the playback speed-up, then wouldn't the wind speed / angle also need to be recalculated? And why would any of this be useful?
VDR playback does not recalculate anything.
An instrument designed to calculate speed from change of position over time of course is affected by the playback speed, which "simulates" bigger change in position over shorter time.
Wind speed has absolutely nothing to do with speed of playback, position change and time.
nohal is offline   Reply With Quote
Old 17-05-2018, 16:43   #7
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 4,368
Images: 4
Re: playback VDR from recorded file

Quote:
Originally Posted by nohal View Post
VDR playback does not recalculate anything.
An instrument designed to calculate speed from change of position over time of course is affected by the playback speed, which "simulates" bigger change in position over shorter time.
Wind speed has absolutely nothing to do with speed of playback, position change and time.
OK, but *what* instrument is calculating the speed in this playback scenario? And shouldn't this "instrument" also be looking at the timestamps in the sped-up data?

And why wouldn't the True Wind data be affected as well? If the recalculated speed is deemed valid, then the True/Apparent wind angles should be affected as well.

Sorry, but this makes no sense to me. The speed displayed during fast playback should not be accelerated. The wind data should also be unaffected. The displayed time should reflect the playback speed.

Which VDR plugin is being discussed here? I should probably install it and try it out before I get even more confused.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 17-05-2018, 16:53   #8
Registered User

Join Date: Feb 2010
Location: On the go. Not in Prague.
Posts: 4,527
Re: playback VDR from recorded file

Quote:
Originally Posted by Paul Elliott View Post
OK, but *what* instrument is calculating the speed in this playback scenario? And shouldn't this "instrument" also be looking at the timestamps in the sped-up data?

And why wouldn't the True Wind data be affected as well? If the recalculated speed is deemed valid, then the True/Apparent wind angles should be affected as well.

Sorry, but this makes no sense to me. The speed displayed during fast playback should not be accelerated. The wind data should also be unaffected. The displayed time should reflect the playback speed.

Which VDR plugin is being discussed here? I should probably install it and try it out before I get even more confused.
https://opencpn.org/OpenCPN/plugins/vdr.html and yes, you should probably install it to see what it actually does and, more importantly, what it does not.
nohal is offline   Reply With Quote
Old 17-05-2018, 17:03   #9
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 4,368
Images: 4
Re: playback VDR from recorded file

I can't get it to load. I'm running OCPN 4.8.2, and downloaded and ran the VDR install file. I've restarted OCPN several times and can't find VDR in the list of plugins. There's no mention of VDR in the OCPN log file.

But more important, are you saying that OCPN does show an accelerated SOG when VDR is playing back logfiles at a high speed? This is what the OP reported. If so, I say it shouldn't. As a user that's not what I would want to see.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 17-05-2018, 17:27   #10
Registered User

Join Date: Feb 2010
Location: On the go. Not in Prague.
Posts: 4,527
Re: playback VDR from recorded file

Quote:
Originally Posted by Paul Elliott View Post
I can't get it to load. I'm running OCPN 4.8.2, and downloaded and ran the VDR install file. I've restarted OCPN several times and can't find VDR in the list of plugins. There's no mention of VDR in the OCPN log file.

But more important, are you saying that OCPN does show an accelerated SOG when VDR is playing back logfiles at a high speed? This is what the OP reported. If so, I say it shouldn't. As a user that's not what I would want to see.
No, I am not saying anything like that, OpenCPN, where designed to show SOG as received in the NMEA stream, shows the value received, as far as I can say, even when the input comes accelerated from the VDR plugin. If it does not, it is a bug. I can not find any such place playing (BTW your) recorded data with the VDR plugin at any speed.
Where designed to calculate it from position change over time, it shows the value calculated so. This is by design for cases where SOG data from the instruments is not available or wrong and the user does not want to use it. As far as I can tell this also works as expected.
If the OP has a problem, we simply need more input to asses if it is a real problem and worth a fix or a change or not.
nohal is offline   Reply With Quote
Old 17-05-2018, 17:59   #11
Registered User
 
rgleason's Avatar

Join Date: Mar 2012
Location: Boston, MA
Boat: 1981 Bristol 32 Sloop
Posts: 11,169
Re: playback VDR from recorded file

Paul, perhaps you have multiple/parallel installs?
It should work, as I've used it a lot with 4.8.0,4.8.2 and 4.8.4 etc. Perhaps you are linux? Don't remember.
You could try this one.




PS: These are good questions. I can say as I know the answers though.
Attached Files
File Type: pdf vdr_pi-0.4-win32.exe.pdf (233.7 KB, 10 views)
rgleason is online now   Reply With Quote
Old 17-05-2018, 18:36   #12
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 4,368
Images: 4
Re: playback VDR from recorded file

Quote:
Originally Posted by nohal View Post
No, I am not saying anything like that, OpenCPN, where designed to show SOG as received in the NMEA stream, shows the value received, as far as I can say, even when the input comes accelerated from the VDR plugin. If it does not, it is a bug. I can not find any such place playing (BTW your) recorded data with the VDR plugin at any speed.
Ok, I must have misunderstood your earlier post. The behavior you describe sounds very reasonable.

Quote:
Where designed to calculate it from position change over time, it shows the value calculated so. This is by design for cases where SOG data from the instruments is not available or wrong and the user does not want to use it. As far as I can tell this also works as expected.
If the OP has a problem, we simply need more input to asses if it is a real problem and worth a fix or a change or not.
This part is a bit problematic. If the speed calculation does not also use the GPS timestamp (which will also be sped-up during VDR high-speed playback), I would consider that a bug. And by the same reasoning that produced the accelerated SOG, any resulting AW/TW calculations would also be affected. But someone else might reasonably disagree with me on this point. I wasn't even aware that OCPN could do its own SOG calculations.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 17-05-2018, 18:41   #13
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 4,368
Images: 4
Re: playback VDR from recorded file

Quote:
Originally Posted by rgleason View Post
Paul, perhaps you have multiple/parallel installs?
It should work, as I've used it a lot with 4.8.0,4.8.2 and 4.8.4 etc. Perhaps you are linux? Don't remember.
You could try this one.
That's the same VDR I just tried to install. It went into the "C:\Program Files (x86)\OpenCPN\plugins" directory. I'm running this on a fairly new MINIX computer, under Win10/64. It's a clean install, with no previous OCPN versions. My big, fancy, new, fast Dell PC stopped working last night so today I'm using the little MINIX -- which I got for testing.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 18-05-2018, 06:19   #14
Registered User
 
rgleason's Avatar

Join Date: Mar 2012
Location: Boston, MA
Boat: 1981 Bristol 32 Sloop
Posts: 11,169
Re: playback VDR from recorded file

That looks like a correct installation location for a new install. I just tried the VDR_pi-0.4 installed into Opencpn v4.8.4 and v4.8.2 and they both seem to work using a small file from Hartmut which is attached.

I've also attached some screenshots of the install process and the operation of VDR.

I wonder what it is that is causing the problem. I wonder if you have a parallel install? C:\Program Files (x86)\OpenCPN 4.8.2

You'll need too remove the pdf on the harmut file and unzip.

BTW Paul, thank you for your help with posting the new sticky. It will help users find appropriate threads so that searches for answers are more effective.
Attached Thumbnails
Click image for larger version

Name:	Screenshot (96).jpg
Views:	25
Size:	398.7 KB
ID:	169982   Click image for larger version

Name:	Screenshot (98).jpg
Views:	25
Size:	263.6 KB
ID:	169983  

Click image for larger version

Name:	Screenshot (99).jpg
Views:	23
Size:	221.1 KB
ID:	169984  
Attached Files
File Type: pdf Hartmut-AN-Markermeer-Wind-AIS-3m.7z.pdf (514.1 KB, 7 views)
rgleason is online now   Reply With Quote
Old 18-05-2018, 08:55   #15
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 4,368
Images: 4
Re: playback VDR from recorded file

Quote:
Originally Posted by rgleason View Post
That looks like a correct installation location for a new install. I just tried the VDR_pi-0.4 installed into Opencpn v4.8.4 and v4.8.2 and they both seem to work using a small file from Hartmut which is attached.
Thanks. I got it to work -- turns out that I had been installing my programs on a different SD-card "drive", since this MINIX computer has a tiny SSD for "C:" that barely fits Win10 by itself. I had let the VDR install itself on "C:". I moved it over to the proper drive and now it works.

And playing back one of my own logfiles shows the original SOG regardless of the playback speed. This is what I would expect.
__________________

__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Reply

Tags
record

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
First Recorded Shark Attack in SF Bay Saleen411 Off Topic Forum 12 24-10-2015 22:15
Possible issue with AIS and VDR playback??? RhythmDoctor OpenCPN 4 24-03-2015 22:01
AIS Simulation - Run VDR to play AIS Nmea file rgleason OpenCPN 16 12-01-2013 10:28
Opencpn Recovery of Recorded Tracks???? goodwinds OpenCPN 1 14-09-2012 16:13
How to Convert "*.route" Route File into ".*wpt" File To Be Used in Maxsea V.10 doiroda Navigation 6 09-07-2011 23:53



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 12:08.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.