Compute MSA

This function is used to compute the Minimum Specific Acceleration (MSA). This is the absolute value of the norm of the acceleration minus 1 g, i.e., the amount that the acceleration differs from the gravity value. This is always equal to or less than the actual specific acceleration if A is correctly calibrated.

Usage

msa(A, ref)

Arguments

A

An nx3 acceleration matrix with columns [ax ay az], or a tag sensor data list containing acceleration data. Acceleration can be in any consistent unit, e.g., g or m/s^2. A can be in any frame as the MSA is rotation independent.

ref

The gravitational field strength in the same units as A. This is not needed if A is a sensor structure. If A is a matrix, the default value is 9.81 which assumes that A is in m/s^2. Use ref = 1 if the unit of A is g.

Value

A column vector of MSA with the same number of rows as A, or a tag sensor data list (output matches input). m has the same units as A.

Details

Possible input combinations: msa(A) if A is a list, msa(A,ref) if A is a matrix.

Note

See Simon et al. (2012) Journal of Experimental Biology, 215:3786-3798.

See also

odba, njerk

Examples

sampleMatrix <- matrix(c(1, -0.5, 0.1, 0.8, -0.2, 0.6, 0.5, -0.9, -0.7),
  byrow = TRUE, nrow = 3, ncol = 3
)
msa(A = sampleMatrix, ref = 1)
#> [1] 0.1224972 0.0198039 0.2449900