APPENDIX
We describe the formulas for the Kalman filtering steps here. The notation
we use is the same as that discussed in the section on the Kalman filter.
- Evaluate and using the state equation.
 - Find the observation YtandRby observing the system. Note that we
have the matrix Hdefined as follows: 
Yt=HXt+vt- Compute the Kalman gain Kt.
 - Evaluate given by.
 - Evaluate.
 
ˆˆ
Ptt||KH Ptt KH KRKT T=−() (^11) − 1 ()− +
ˆ
Ptt|ˆˆ
XKYHXtt||−− 11 +−t( t tt )ˆ
Xtt|KPHHPH Rtt=+T()t T−
ˆˆ
1ˆˆ
ˆˆ
||
||XAX
PAPA
tt t t
tt t tT−−−
−−−=
=
111
111ˆ
Ptt|− 1ˆ
Xtt|− 1Kalman Filtering 69