How to interpret nacp or nacv from operational_status_data4 table.

Greetings,

The opensky documentation does not give details about the operational_status_data4 columns, instead  refer to RCTA DO-260B standard for us to interpret columns.
From my understanding of the DO-260B standard, nacp values are in range [0,11] and nacv [0,4].

However, when checking the database, nacp values are in range [0,15] and nacv [0,7], and to avoid misunderstanding, planes with these values exists, range are not extracted from the columns fields type.

Example with a SQL Distinct on the month of july :

SELECT DISTINCT(positionnac)
FROM operational_status_data4
WHERE hour between 1688169600 and 1690848000
ORDER BY positionnac;

Are the values rescaled from the ADS-B frame or should we ignore the planes with these values ?

Thanks.

We just discussed this. These values in the operational_status_data4 are not correctly decoded. You should re-decode the NAC values from the raw messages with pyModeS.
I hope this helps.

Thanks you very much for your reply.  
  
First off, I extracted a rawmsg linked to a value out of range from the database and re-decoding it with pyModeS gave me the same value. So the problem seems to come from the rawmsg itselves.
  
Second, I was curious to know if these problems are quite localized so I craft a little map to show where the plane with these score are.
 
Caption: Area flight over by plane with incoherent score from the month of july 2023
A very little number of planes are also located in asia, but most of them are on the screenshot. I didn't take time to check if the messages came from specific receiver or not, it's hard to say what the problem's root is.

Do you think you know the source of the problem and how to solve it?
Would it be possible to specify this fact in the documentation?
If need be, I can lend a hand.

Thanks

First and foremost,I went back to read the DO-260B references transcriptions or any linked documents and I found some additional information. I found on the icao int website some documents - like ADS-B-LEG-IP02 - with the explicit mention of nacp values in the range [0,15].
The values [12,15] are defined as *reserved*, so I won't investigate further to know what is behind.
You mentionned the 1090Mhz riddle, I think the reserved values worth the mention to avoid confusion.

Reserved values are mentionned for the nacp, however there is none for the nacv field. I couldn't get any document explaining the values [5, 7] found.

I hope this post will help and I'll try to dig a little bit more.