Track Replay

[jvde-github]

We have added the option to replay vessel tracks — animate the traffic your station received, scrub through time, or watch it play back at up to 300× speed. It is already live on aiscatcher.org/blackfield01: choose replay from the top right map buttons.

Under the hood, track storage has been reworked into a tiered in-memory store: the most recent hour is kept at full resolution, older history is thinned out, and once the budget is full the oldest history is overwritten first. Total memory consumption is configurable via the new webserver setting TRACK_MEMORY (in KB), for example TRACK_MEMORY 4096 for a 4 MB budget — which is also the default in server mode (1 MB otherwise).

Note that the store is not persistent: replay covers what the station has seen in the current session, and history is lost on a restart.

[jvde-github]

This is a pilot being put on board of a cargo vessel

Screen.Recording.2026-08-04.at.23.57.08.mov

[andlil]

I really like this feature, playback is butter smooth!

[jvde-github]

It's is fascinating to watch animated, you see new patterns in the data

[Phil353556]

"new patterns in the data" you're right. Data are there, but it is now possible to make the invisible visible
That's great

[jvde-github]

Screen.Recording.2026-08-07.at.19.37.01.mov

[Phil353556]

Hello,
One question:
How does the recording work?
-is the browser needs to be open on the webpage to capture and record?
OR
-is this done at the server level? so the browser can be open when the user wants, the historical will be available?

Reading the sentence "Note that the store is not persistent: replay covers what the station has seen in the current session, and history is lost on a restart" I undersand this is second option. is it right?

Thanks - That's a great functionnality!!
Phil

[jvde-github]

yes, it is done in ais-catcher on the server side but in memory and it is not written to disk. so, if you restart the program, it starts accumulating again but the browser does not have to be on.

[Phil353556]

Perfect, thanks for this quick reply, as usual.
Phil

[andlil]

This has to be one of the coolest features added in a long time! Just being able to view tropo in "realtime" is amazing!

Skarminspelning.2026-08-10.kl.06.52.12.mov

[jvde-github]

Cool!

[jvde-github]

Especially how it aligns with the short and long term station ranges!

[Phil353556]

Hi Jasper,

If my understanding is correct: the replay time is one hour.
If there a way to increase the replay time, to two, three, four, five, six hours?

Thank you
Phil

[jvde-github]

In the managed web viewer (where you can configure the program), there is an option "max track age":

By default this is set to one hour, zero is no limit (which essentially is then driven by the amount of memory allocated). If you are using command line settings, I think it is -N track_time 0 after the -N with the port for max replay.

[Phil353556]

Hello, Thanks
I tried with config.cmd and parameter configured to 21600 .. 6 x 3600s but still one hour on UI
Does that mean Track Memory must be configured too. What is the right name for config.cmd? -N Track_Memory ?
if it is that, 1024 (KB) for one hour so 6144(KB) for six hours, for example ?
Thanks for your answer / Phil

 # -----------------------------------------------------------
# Track time
-N track_time 21600
# -----------------------------------------------------------

[jvde-github]

Should be fine, assuming this line is after -N port number. Have you waited longer than an hour? 1MB is sufficient for more than 12 hours...

[Phil353556]

Yes,
I updatedthe file config.cmd yesterday and look this morning

ps -ef |grep AIS shows:
/usr/bin/AIS-catcher -G level debug -o 0 -C /etc/AIS-catcher/config.json @/etc/AIS-catcher/config.cmd

and grep shows:
$ grep track /etc/AIS-catcher/config.cmd
-N track_time 21600

track_time: lowercase hum may be it is uppercase, but in the documentation I read lowercase

Phil

[jvde-github]

Should be ok, maybe there is also a track_time in the config.json contradicting.

Maybe you can install latest? The track time is now in the stats tab. We can see what the program assumes.

[Phil353556]

Update done: thanks you

contents of config.json, not used yet, I think ....

$ cat /etc/AIS-catcher/config.json
{"config":"aiscatcher","receiver":[{"input":"rtlsdr","verbose":true}],"version":1,"server":[{"port":8100,"station":"My Station","lat":0,"lon":0,"webcontrol_http":"","backup":10,"history":1800,"context":"settings","active":true,"share_loc":false,"realtime":false,"geojson":false,"prome":false,"log":false,"decoder":false,"zone":[]}]}

Nothing changes after upgrade, 1h so I moved the -N track_time 21600s AFTER the standza
-N 8383 FILE /etc/AIS-catcher/stat.bin BACKUP 10 ABOUT /home/phermes/about.md
and that's Ok,

Thank you Jasper!

Phil

[Phil353556]

@jvde-github
this functionnality : track replay is really a game changer for AIScatcher, thank you so much for this, that's great
May I suggest one minor enhancement?
add a - (minus sign) and a + (plus sign) to decrease / increase the speed of replay
currently a click only allow the increase?
' - ' before (so on the left) the speed written
' + 'after (so on the right) the speed written
example: - x300 +
Regards
Phil

[jvde-github]

Thanks, will have a look how it can be fit in the bar.

Btw, working on the same feature for the community map, not as smooth yet, but hopeful can offer replay for last 4h...

replay-Preset1280x720.mp4

[jvde-github]

Bremerhaven today (Sun August), just under 4 hours in 22 seconds. It is fascinating to see port operations all over the world. I am checking if the server can cope, and if so will roll out the functionality on aiscatcher.org. Panning/zooming and time scrubbing now is smooth globally while running a playback :-)

Screen.Recording.2026-08-16.at.13.44.35.small.mp4

[jvde-github]

If you "follow" a ship and then "replay" it feels like you are in an arcade game :-)

Screen.Recording.2026-08-20.at.21.20.59.compressed.mp4