a2pr.RdPitch and roll estimation from triaxial accelerometer data. This is a non-iterative estimator with |pitch| constrained to <= 90 degrees. The pitch and roll estimates give the least-square-norm error between A and the A-vector that would be measured at the estimated pitch and roll. If A is in the animal frame, the resulting pitch and roll define the orientation of the animal with respect to its navigation frame. If A is in the tag frame, the pitch and roll will define the tag orientation with respect to its navigation frame.
a2pr(A, sampling_rate = NULL, fc = NULL)
| A | An nx3 acceleration matrix with columns [ax ay az] or acceleration sensor list (e.g., from readtag.R). Acceleration can be in any consistent unit, e.g., g or m/s^2. |
|---|---|
| sampling_rate | (optional) The sampling rate of the sensor data in Hz (samples per second). This is only needed if filtering is required. If A is a sensor data list, sampling_rate is obtained from its metadata (A$sampling_rate). |
| fc | (optional) The cut-off frequency of a low-pass filter to apply to A before computing pitch and roll. The filter cut-off frequency is in Hertz. The filter length is 4*sampling_rate/fc. Filtering adds no group delay. If fc is not specified, no filtering is performed. |
A list with 2 elements:
p: The pitch estimate in radians
r: The roll estimate in radians
Output sampling rate is the same as the input sampling rate.
Frame: This function assumes a [north,east,up] navigation frame and a [forward,right,up] local frame. In these frames, a positive pitch angle is an anti-clockwise rotation around the y-axis. A positive roll angle is a clockwise rotation around the x-axis. A descending animal will have a negative pitch angle while an animal rolled with its right side up will have a positive roll angle.
if (FALSE) { samplematrix <- matrix(c(0.77, -0.6, -0.22, 0.45, -0.32, 0.99, 0.2, -0.56, 0.5), byrow = TRUE, nrow = 3 ) list <- a2pr(samplematrix) }