# Gaussian Filter

Gaussian Filters is a tractable implementation of the Bayes filter (Bayes Filter) for continuous spaces.

## Key Idea

Beliefs are represented by a multi-variate normal distribution.

$$p(x) = \text{det}(2 \pi \Sigma)^{-\frac{1}{2}} \text{exp} \left( - \frac{1}{2} (x -\mu)^T \Sigma^{-1} (x- \mu) \right)$$

The density of variable $$x$$ is characterized by mean $$\mu$$ and covariance $$\Sigma$$.

## Ramifications

Since beliefs are represented by a multi-variate normal distribution, this means that beliefs are uni-modal. This is suitable for many tracking problems. However, this is a poor match for many global estimation problems with multiple hypotheses that should give rise to their own modes in the posterior.

## Representations

moments representation
The Gaussian is represented by its mean and covariance (first and second moments)

canonical representation :

These representations have a bijective mapping, and are functionally equivalent, but give rise to different algorithms.

Using the moments representation gives rise to the Kalman Filter.