System equation of a calibration line with drift

2 System equation of a calibration line with drift 

In this section we derive a system equation which describes a drifting calibration line. Let us suppose that the intercept jC (/ + 1) at a time y + 1 is equal to xfj) at a time j augmented by a value a(j), which is the drift. By adding a non-zero system noise to the drift, we express the fact that the drift itself is also time dependent. This leads to the following equations [5,6]  

A similar equation can be derived for the slope, where P is the drift parameter  

Equations (41.12) and (41.13) can now be combined in a single system model which describes the drift in both parameters  

F describes how the system state changes from time t, to 

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