DF = 18 TC = 6 message bds30?

[ElSabio97]

Hi again @junzis !

I'm downloading tiny bits of data using @xoolive rawdata query like this:

from traffic.data import eurofirs
from traffic.data import opensky
import pyModeS as pms

df = opensky.rawdata(
    start="2020-07-12 14:00",
    stop="2020-07-12 14:01",
    bounds = eurofirs['LECB'],
    cached = True
)

df.data['DF'] = df.data['rawmsg'].apply(lambda x: pms.df(x))
df.data['TC'] = df.data['rawmsg'].apply(lambda x: pms.typecode(x))

df.data['BITSlength'] = df.data['rawmsg'].apply(lambda x: len(pms.hex2bin(x))) #gives the ones that are 112 bits long, otherwise is30 will return error.

dfprebds30 = df.data.loc[df.data['BITSlength'] == 112].copy() #take only the ones 112 bits long to a new df.

dfprebds30['BDS30'] = dfprebds30['rawmsg'].apply(lambda x: pms.bds.bds30.is30(x)) #check which ones are actually BDS30

dfisBDS30 = dfprebds30.loc[dfprebds30['BDS30'] == True].copy() #take only the BDS30 to another df for easier data visualization.

If you run that code, you will get 77 messages that are BDS 30 BUT have DF18 and TC6.

From what I understand only DF 20/21 can provide BDS30 messages. What am I missing?

If you want to check faster what I'm trying to say you can run the following commands to check one of those 77 messages:

print(pms.df("903433d7300007b48cb9a983db26"))
print(pms.typecode("903433d7300007b48cb9a983db26"))
print(pms.bds.bds30.is30("903433d7300007b48cb9a983db26"))

[junzis]

Indeed, you should always check the downlink format (make sure it is 20 or 21) before inferring the BDS code.

I can't speak for the traffic library, but I think the rawdata may also have formats other than 20/21.

Also, don't use bds30.is30(), this only tells you if the message has the possibility of being a BDS 30 message. You should use pms.bds.infer() instead. This will give you all the possible BDS codes of the message. Then keep the ones with only BDS30.

[xoolive]

yes rawdata requests by default from all tables (documentation) but you may limit to DF 20 and 21 if you limit yourself to the rollcall table.