# Tag Info

The IMU senses deviations from gravity within the inertial frame. Essentially, IMU measures the specific force $f_b$ given in the base frame as: $$f_b = R^{bn}(a_{ii}^n-g^n),$$ where $g^n$ is the gravity in the navigation frame (NED), $a_{ii}^n$ is the inertial acceleration expressed in NED frame and, finally, $R^{bn}$ is the rotation matrix from NED to ...
The simplest way to construct $$x \sim p(x_t | x_{t-1}, u)$$ if you have $$x_t = Ax_{t-1}$$ is to just use $$x_t = Ax_{t-1} + \mathcal{N}(0,R)$$ where R is some process noise. You may way to sample from a more complex distribution. Similarly, to construct $$p(z_t | x_t)$$ you can just use $$\mathcal{N}(Cx_t,Q)$$ (again you may want to use some more complex ...