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4.2.6.1 State identification 
In state identification, a distinction is made between “primary” and “derived” state variables. Primary 
state variables are based on data types which are supplied directly by sensors. Derived state variables 
are calculated by the combination of various state variables. It should be borne in mind that this defini 
tion relates solely to the method with which the variable concerned is calculated, and not to the variable 
itself. For this reason it is possible that the same state variable is considered both as a “primary” and 
“derived” state variable (see state variable “LATLONxy”: primary state variable from the position sensor - 
DFD 5.1.1.1 and derived state variable from dead reckoning - DFD 5.1.2.4). 
DFD 5.1 : State identification