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ADL / Golze satellite weather system

Aggregation, treatment and diffusion time?

EGTF, LFTF

Maybe because it goes through AFTN, which is a message-based network with a potentially high latency. AFTN messages are typically delivered within several seconds, but occasionally may take up to several minutes.

LKBU (near Prague), Czech Republic

Radar images going via the AFTN?

What happened to that OPERA consortium, set up to market the data?

Administrator
Shoreham EGKA, United Kingdom

@Sebastian_G

Could you tell us, approximately, what cost increase would imply going from 15min to 10 or 5 minutes latency with your system ?
Would you be able to ask your provider such a “switch” ?

Last Edited by PetitCessnaVoyageur at 10 Jun 12:48

Bear in mind that the data costs would increase as well.

EGKB Biggin Hill

So we can’t really know the relative postions of plane and convective cells. It’s rather poor resolution (big pixels) and is updated every 5 minutes. It’s rather clear that we can’t provide remote weather avoidance with such system.

I guess that 5 minutes is not that bad. Better than 15. And AFAIU the main purpose is not for ATC to provide weather avoidance, but rather to have an overall picture of the weather in order to identify the hotspots and avoid sending planes into a hold where there is a big cell brewing.

Is the 5 minutes a technical limitation due to data processing and transfer? What is the situation in the US? How much delay do they have in their overlays? And Germany?

LFPT, LFPN

Quite a number of questions in this thread. I am sorry the answer below is a little longer:

1) Average age of displayed radar data

From a practical point of view what counts is the average age of the radar image when displaced in the cockpit. The math is as follows:

Average age of displayed radar data is the sum of:

A) Half of data acquisition interval
B) Data processing and transmission time
C) Half of data update interval

For the current “15min” radar date used by the ADL this comes down to:
2,5min (A) + 4min (B) + 7,5min(C) = 14min

In comparison this would be the “5min” radar data which can be purchased for central Europe:
2,5min (A) + 12min (B) + 2,5min(C) = 17min

So the average age of the displayed data would actually decrease by using this “5min” data. The main reason is the 12min data processing and transmission time. I have no idea why this is so long but this has not changed for several years and the weather service experts tell me they somehow can not get it done much faster.

→ The reason the ADL system currently does not provide “5min” radar updates is because the average age of the displayed data in the cockpit would not decrease.

2) Hidden delays in radar data / timestamping schemes

There are different system of timestamping radar data. In Europe the moment of the last meteorological data contained is used as the timestamp. So the actual image is a mix of measurements taken at different moments before the timestamp. The interval between the first and last measurement is confidential but my contacts indicate that it is currently about 5 minutes maximum.

In the US things are completely different. There the timestamp is the moment of the publication. So all their data appears to be a few minutes younger but actually it isn’t. They just hide the processing and transmission times from the user. This also explains why even though they have 5min updates in the US they still have significant lag in their data.

3) Differences in radar quality

In weather radar there is a constant trade off between quality and update frequency. On board weather radar provides updates about every 5 seconds but this is at the cost of quality. A wide beam is moved across the area once. You get a lot of ground clutter, limited range due to the wide beam etc.
Ground based weather radar is a lot more sophisticated and usually each image is made from many “turns” of the antenna at different beam angles, in different modes etc. This means that update frequencies can not bet increased beyond 5min because the antenna simply can not turn faster. For Germany for example the 15min data is actually a bit better quality than the 5min data because of different measurement technologies used.

4) Mapping imperfections / Ranging errors

Even is there was a way to increase the update frequency I noticed there are undocumented small imperfections in the mapping respectively range accuracy of the weather radar systems. When comparing with on board data I saw errors up to about 2 nautical mile. I later analysed radar data from later timestamps but that did not explain it. So for many reasons like a wide radar beam combined with slant range effects or a far away antenna etc. there will always be a small error. So ground based weather radar will always require to fly in some safe distance to cells anyway. This limits the practical advantage of higher update frequencies.

5) Pricing

The weather services usually charge per image so “5min” data is roughly three times the price of “15min” data. So far I never came across different pricing based on the delay of the data. For strikes such pricing exists but not for radar. Transmissions costs would also be roughly three times as much for “5min” data. So overall a factor 3 price increase would be realistic.

6) Weather radar and ATC

There are obviously differences but many ATC units seem to get the same data we as end users get with a similar delay. Sometimes they can overlay it directly on their screen and sometimes they have to open it on another screen and do the georeferencing kind of manually. Only in some rare cases the ATC primary radar seems to have some kind of “weather mode” where the actual radar side of the ATC station provides weather data in real time (with all associated quality imperfections due to wide beam etc.).

→ Beware of what ATC tells you. One US controller tried to vector me right into a cell as the lady did not seem to be aware that her data did have time lag. And she insisted I should go there even though I did see the data link picture, on board radar picture and had a look out of the window.

Many pilots praise US ATC but from my experience this only helps if you are not equipped. If you have data link weather and if possible on board radar all those reminders never really pointed out anything I did not already know. I actually prefer the European way: The pilot alone decides where to go and ATC does great efforts to make it possible instead of saying “it does not look so bad on my screen why do you want to change heading”.

www.ing-golze.de
EDAZ

Many thanks Sebastian for sharing your knowledge.

Would you also have an interesting picture of a ground weather radar ? And also, maybe, a map of the ground weather radar network through Europe ?
The material aspect is obscure for me !

Last Edited by PetitCessnaVoyageur at 11 Jun 06:35

@PetitCessnaVoyageur, I am not sure if you are just asking for a screen shot from the ADL, but if you are, this is a particularly interesting one. It is three years old, so the software has been updated, but the point is well made.

In this scenario, I was flying from NW France to EGKB Biggin Hill (which is at the western end of the green line, near London.)

The green line is the clearance I was given, a STAR. It has been automatically crossfilled from my GPS.

I could see from 100 miles away that that took me through some serious weather, so from just northeast of Guernsey I asked for a different route to avoid, and was given the magenta line.

I can think of no better example of why you would want such a box.

EGKB Biggin Hill

Timothy, I think it was more this he was after.

EGTK Oxford
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