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Old 04-06-2019, 11:23   #1
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Increase "Own Vessel" render update time

I was wondering if it were possible to increase (or decrease) the render update time for the "own vessel" when using GPS NMEA stream as input connection.

Currently, I think the update time is 1 second. (Chances are I might have missed something very obvious in the settings, in that case, my apologies.)


Thanks!
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Old 04-06-2019, 12:08   #2
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Re: Increase "Own Vessel" render update time

Quote:
Originally Posted by imp-cruiser View Post
I was wondering if it were possible to increase (or decrease) the render update time for the "own vessel" when using GPS NMEA stream as input connection.

Currently, I think the update time is 1 second. (Chances are I might have missed something very obvious in the settings, in that case, my apologies.)


Thanks!
The frequency of updates from most of "normal" GPS units is 1Hz, which means once per second.
Unless of course you explicitly bought one that supports higher update frequency, in which case you have to use the configuration software for that GPS unit to switch it to the mode where it produces the data more frequently.
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Old 04-06-2019, 13:11   #3
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Re: Increase "Own Vessel" render update time

Quote:
Originally Posted by imp-cruiser View Post
I was wondering if it were possible to increase (or decrease) the render update time for the "own vessel" when using GPS NMEA stream as input connection.

Currently, I think the update time is 1 second. (Chances are I might have missed something very obvious in the settings, in that case, my apologies.)


Thanks!

What are you trying to achieve?



But anyway try this:
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Old 04-06-2019, 13:21   #4
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Re: Increase "Own Vessel" render update time

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Originally Posted by nohal View Post
The frequency of updates from most of "normal" GPS units is 1Hz, which means once per second.
Unless of course you explicitly bought one that supports higher update frequency, in which case you have to use the configuration software for that GPS unit to switch it to the mode where it produces the data more frequently.

For testing purposes I streamed NMEA data ($GPRMC) over the network (TCP). I can play with the update frequency (and my original NMEA file already updates every 0.1 second); however, the vessel's position in the viewer only changes every second? Am I missing something?

I tried checking the source (and changed some parameters), but did not find a specific parameter or function related to this so far (I realize the code is quite extensive and I might have looked into the wrong files :-)).
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Old 04-06-2019, 13:30   #5
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Re: Increase "Own Vessel" render update time

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What are you trying to achieve?

But anyway try this:

For now, I was just streaming NMEA data over the network (TCP) for simulation purposes. I do plan on sailing using realtime iGNSS as input, but so far I was looking into the possibilities of the viewer. Consequently, faster update times of the vessel location could be useful (I'm testing some custom waypoint following methods, among other things, using OpenCPN as visual feedback).
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Old 04-06-2019, 14:56   #6
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Re: Increase "Own Vessel" render update time

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Originally Posted by imp-cruiser View Post
For now, I was just streaming NMEA data over the network (TCP) for simulation purposes. I do plan on sailing using realtime iGNSS as input, but so far I was looking into the possibilities of the viewer. Consequently, faster update times of the vessel location could be useful (I'm testing some custom waypoint following methods, among other things, using OpenCPN as visual feedback).

Have you tried changing the update time that I highlight? Do you really need updates more frequently than 1 second?


Are you trying to use course up?


Is the ownship icon you need to update faster, or the highway in the route popup window?



Chris
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Old 04-06-2019, 15:51   #7
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Re: Increase "Own Vessel" render update time

Quote:
Originally Posted by imp-cruiser View Post
For testing purposes I streamed NMEA data ($GPRMC) over the network (TCP). I can play with the update frequency (and my original NMEA file already updates every 0.1 second); however, the vessel's position in the viewer only changes every second? Am I missing something?

I tried checking the source (and changed some parameters), but did not find a specific parameter or function related to this so far (I realize the code is quite extensive and I might have looked into the wrong files :-)).
If you do not enable the data filter mentioned by Moo, the ownship is updated as fast as the data is available and technically possible. It is much faster than once per second on all systems I have ever seen.
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Old 04-06-2019, 16:46   #8
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Re: Increase "Own Vessel" render update time

I have hacked in support to update AIS targets in realtime since they often get updates only 20 seconds and less if you miss a message.

This draws a different color boat in the "extrapolated position" in addition to the normal boat which is at the last message location. I didn't submit this yet, it adds another checkbox to the ais options unfortunately. It doesn't utilize turn rate in the calculation. I'm not sure it should.

I sometimes wonder if AIS could transmit intended future course, like the route the autopilot is following which could improve this even more if there are turns ahead and it would be interesting to plot these, but I don't think AIS standard supports this.


I also draw the planes in a similar way showing realtime positions from the adbs rendering in the rtlsdr plugin.
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Old 04-06-2019, 23:03   #9
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Re: Increase "Own Vessel" render update time

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Originally Posted by Moo View Post
Have you tried changing the update time that I highlight?
Yes, nothing changes (both for increase and decrease).

Quote:
Originally Posted by Moo View Post
Do you really need updates more frequently than 1 second?
Well, not really; however, the real vessel is rather small, and for testing (simulating), for instance, a collision avoidance program (outside OpenCPN), using OpenCPN merely as a visual feedback tool, it would be useful. Ultimately, AIS as well as ENC chart objects from OpenCPN could be used as complementary data, as it already provides interpretation for this.

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Originally Posted by Moo View Post
Are you trying to use course up?
I tried both ways (north up and course up).

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Originally Posted by Moo View Post
Is the ownship icon you need to update faster, or the highway in the route popup window?
The ownship icon (for now)
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Old 04-06-2019, 23:14   #10
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Re: Increase "Own Vessel" render update time

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If you do not enable the data filter mentioned by Moo, the ownship is updated as fast as the data is available and technically possible. It is much faster than once per second on all systems I have ever seen.
For example, my .nmea looks like this (for less than two seconds):

$GPRMC,104242.90,A,5108.05362, ...
$GPRMC,104242.92,A,5108.05362, ...
$GPRMC,104242.94,A,5108.05362, ...
$GPRMC,104242.96,A,5108.05362, ...
$GPRMC,104242.98,A,5108.05362, ...
$GPRMC,104243.00,A,5108.05361, ...
$GPRMC,104243.02,A,5108.05361, ...
$GPRMC,104243.04,A,5108.05361, ...
$GPRMC,104243.06,A,5108.05361, ...
$GPRMC,104243.08,A,5108.05361, ...
$GPRMC,104243.10,A,5108.05361, ...
$GPRMC,104243.12,A,5108.05361, ...
$GPRMC,104243.14,A,5108.05361, ...
$GPRMC,104243.16,A,5108.05361, ...
$GPRMC,104243.18,A,5108.05361, ...
...

Maybe updates only occur when the last character (second) of the timestamp changes (e.g. from 2 to 3)?
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Old 04-06-2019, 23:23   #11
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Re: Increase "Own Vessel" render update time

For this NMEA sequence OCPN does what it get. Even though the RMC message are sent more often the latitude is not changed more than once. So here OCPN does what it should. It may be the GPS sends often but not change the position more than once per second?
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Old 05-06-2019, 05:36   #12
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Re: Increase "Own Vessel" render update time

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For this NMEA sequence OCPN does what it get. Even though the RMC message are sent more often the latitude is not changed more than once. So here OCPN does what it should. It may be the GPS sends often but not change the position more than once per second?
Hm. Position (longitude and latitude) also changes over one second (~0.1 s).
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Old 05-06-2019, 05:40   #13
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Re: Increase "Own Vessel" render update time

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Hm. Position (longitude and latitude) also changes over one second (~0.1 s).
Would you mind posting the actual data? And exact instructions on how to replay them at the speed you are replaying them?
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Old 05-06-2019, 06:28   #14
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Re: Increase "Own Vessel" render update time

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Would you mind posting the actual data? And exact instructions on how to replay them at the speed you are replaying them?

Sure. Temporary link: https://nextcloud.svbaelen.org:444/i...PSMfcLgk5zXmAz

More info on the replay method in file header (stream.py).
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Old 05-06-2019, 06:49   #15
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Re: Increase "Own Vessel" render update time

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Originally Posted by boat_alexandra View Post
I have hacked in support to update AIS targets in realtime since they often get updates only 20 seconds and less if you miss a message.
Do you mean to decrease the update time interval? I guess AIS has a similar minimum of 1 second in the viewport. On the other hand, current AIS systems only allow updates every 2 seconds (tops, up to x minutes, depending on the "Class"). In this case it does not really matter. (Although next generation systems will increase bandwidth, among other improvements, significantly, so this might change in the next few years?)

Quote:
Originally Posted by boat_alexandra View Post
This draws a different color boat in the "extrapolated position" in addition to the normal boat which is at the last message location.
That's interesting! I am planning on doing something similar (drawing "additional object") based on different sources (onboard sensors, AIS, ...)
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