jvde-github
Indicating / measuring enhanced propagation conditions
Jasper,
I have mentioned this before in a slightly different way, before you added the web site graphs.
Would it be possible to add the Base Station and Aid to Navigation total
to the distance chart as a separate line with scale on RHS
My normal total Base plus AtoN is about 6-8, currently it is 12 and there is or recently has been a little more enhanced propagation as shown by the distance chart on the Station Details web page (above).
At this level (4 above average) I often see about 100 NM (as far as Calais):
In my post in discussions last October, there is a screen grab with 566NM distance and 29 base and AtoN stations in total (reproduced below).
I think there is a good correlation between Base and AtoN total and enhanced propagation at the receiving location.
Adding this to the distance graph will enable us to record to help test this and it may be useful as an alarm trigger when above a certain number.
When I mentioned this before, I suggested turning the box on top RHS of the screen a different colour using a value based on the user's Base and AtoN count, above the local 'average'. This could be automated based on a long term average (say 1, maybe 3 months) and a number above this as the alarm trigger. That way each user can set the enhanced propagation alarm to suit their location.
Change colour of above from white to a user selectable colour, perhaps.
The total count to act as a trigger could be added as a parameter, but may be better if it could be stored as a local average (as recorded over a month or so). To test this and use it as an alarm trigger it could just be a parameter used at run-time, likewise, initially the average could also be added as a parameter: 'new parameter' 8 13 where 8 is local average and 13 is the alarm trigger.
What do you think? Happy to discuss further and test it if needed
Regards Roger
Hello Roger,
it is a bit same as this discussion: https://github.com/jvde-github/AIS-catcher/discussions/305
It is a bit of work even to add something simple to make it backward compatible with the history backup so will add something but will take a bit of time.
Hi Jasper,
Thank you. When you have something to test, let me know.
Yes that discussion points in the same direction too.
Roger
Not sure what this is about anymore :-) Propose to close and reopen if any actions needed.
Jasper,
it is about detecting and indicating enhanced propagation conditions.
My suggestion is (having refined my thoughts in the meanwhile):
When conditions are enhanced, the number of fixed and AtoN stations increases. Above a certain number the propagation is enhanced,
I normally see 5-8 or 9 fixed stations Currently 7.
When I see 12-15, I get many more ships in the English Channel and see base stations in France, due south and as far as Calais. That happens quite often during high pressure conditions.
Sometimes (as I documented last year) you get a big one with 20-30 base stations.
Of course this "magic" number indicating enhanced conditions will be different for every feeder being dependent on location and local atmospheric conditions.
I would find it most helpful to have the total number of vessels change colour, the trigger point set as a variable at run time. Or the background of the whole mini information window. In other words a fast but minimally invasive (visually) way to check.
I would set the trigger point here starting at either 12 or 18 ( further refinement needed). A glance at the AIS-catcher screen would show me if conditions are improving or declining. Better to have two settings: Change from white (default) to yellow when (in my example) 12 and change to red above 18.
I think it is a simple way for each user to have the means to set up the "alarm" when conditions improve. Much faster than looking at a zoomed out map or look at the number of vessels moving. Here in the Solent the number of vessels variation is huge sometimes Class B vessels number 3-400 (or more) However the number of Class A vessels changes too and just looking at those on the expanded vessel information window does not show this information instantly, further investigation is required. The number of base stations total Fixed and AtoN is a far more reliable indicator.
Having a graph of this number over time would give a histoirical context to conditions. The total number of vessels over time does not, especially here in the summer where the local vessel count is way above the annual average ratio of class A to Class B. That tends to preclude vessel count as a proxy for analysing conditions.
Using maximum distance is not reliable as there is often an outlier several hundred NM away. I suspect these can come from corrupt AIS data or even aircraft bounced signals.
What do you think?
regards
Roger
See where you are coming from. Thanks for sharing.
Could you look at the average distance as a measure for reception, e.g. average distance over say 15 minute period, vs previous period? This would be less sensitive to outliers and tracking base stations might not work for every user?
Jasper,
The problem is so many outliers and of various origins, I have seen vessels docked at Southampton giving location in Scotland, then reverting to the local docks, then some from Scotland, the same location each time (and not on land) so a viable location. I concluded it was a data error. Not able to get enough data to figure it out: same vessel, not many of them, but enough to distort average distance.
In a different way, if we took the average distance over a 15 min timeframe and I got 3 reports, one locally and two from Scotland (and even on land, if I am not monitoring) then the average would be from 6. NM (local) 480 NM Scotland, 480 NM Scotland = ave 322 NM
an example I captured a while back:
and
and others that confused me as I knew the vessel concerned ( first one below) was 'elsewhere' not in its home port
distance a bit long?
So the above by way of examples that I saw (and I am not at the AIS screen all the time!!!!) and got did not compute in my head.
I may have added too many pictures as the preview does not show all... hopefully you get the idea.
When you add in the aircraft bouncing the signal, yes it does happen, hams use this to make contacts far away e.g from UK to Germany bouncing off aircraft kind of half way, roughly where you live using 144 MHz at 35,000 feet. 162 MHz is not much different. It is possible.
So I am saying we may be chasing errors rather that good data.
I do agree that some folks may not be able to use it but it is worth a test to see if the process holds up. I have spent a lot of time verifying what I see and it does work, when I look at the data (total base and AtoN) and what I see on the map vessel wise.
Hope that helps explain what I think.
Roger
All clear. Will have a think. I see the issue you are describing, have some ideas how to blend it in with new functionality.
Btw, also added some more description on the ducting map I am creating based on weather data: https://aiscatcher.org/analytics/ducting.