# Block 5 — Multi-State Kalman Filter

<p class="block-meta"><span class="b-block">Block 05</span><span class="b-time">~60 min</span><span class="b-demos">2 demos</span></p>

<p class="block-synopsis">Generalizes to a vector state with cross-covariance, runs constant-velocity 4D and Gauss-Markov 6D filters on simulated 2D motion, and shows how a position measurement updates correlated velocity states automatically.</p>

## What you'll learn

1. Explain why navigation problems require multi-state estimation.
2. Generalize the scalar Kalman filter equations to vector states.
3. Write the state transition matrix $\mathbf{F}$ for constant-velocity 2D motion.
4. Write the measurement matrix $\mathbf{H}$ for a position-only sensor.
5. Interpret the off-diagonal terms of the covariance matrix $\mathbf{P}$ as cross-correlation between states.
6. Run a 4-state filter that simultaneously estimates 2D position and velocity from noisy 2D position fixes.

## In this block

<div class="block-toc">
  <a class="bt-card bt-reading" href="L05_MultiStateKF_Reading.html">
    <span class="bt-kind">Reading</span>
    <h4>Reading</h4>
    <p>Vector states, F and H, and cross-covariance.</p>
  </a>
  <a class="bt-card bt-flashcards" href="L05_Flashcards.html">
    <span class="bt-kind">Flashcards</span>
    <h4>Flashcards</h4>
    <p>Click-to-reveal cards for the block's key terms and equations.</p>
  </a>
  <a class="bt-card bt-demo" href="L05_KalmanFilter4D_Demo.html">
    <span class="bt-kind">Demo</span>
    <h4>Demo · 4D Kalman Filter</h4>
    <p>Constant-velocity 4D filter on 2D motion; position fixes correct velocity through cross-covariance.</p>
  </a>
  <a class="bt-card bt-demo" href="L05_KalmanFilter6D_Demo.html">
    <span class="bt-kind">Demo</span>
    <h4>Demo · 6D Kalman Filter</h4>
    <p>Gauss-Markov accelerations: 6D state with position, velocity, and acceleration.</p>
  </a>
</div>

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