AIS message 1, Rate of turn

[Владимир Калачихин]

I am, of course, stupid, but:

https://www.navcen.uscg.gov/ais-class-a-reports :
'Rate of turn' field has 8 bits.
It may contain:
"-127 = turning left at more than 5 deg per 30 s (No TI available)"

How to cram in 8 bits the '-127' number?


Next:
"-128 (80 hex) indicates no turn information available (default)."

But '80 hex' === 128, not the -128.

Can anyone clarify?


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Владимир Калачихин