Apply a sensor calibration to an IMU vector

Transforms raw values from an IMU sensor to physical units (e.g., meters per second squared) using a specified calibration.

Use acc_calibration() to create a calibration for acc vectors.

Usage

transform_imu(x, calibration)

Arguments

x

An IMU vector (acc, mag, or gyro).

calibration

An imu_calibration object whose subclass matches the sensor type of x. Must be the same length as x or length 1, in which case the calibration is recycled to all elements of x.

Currently, only acc_calibration() is supported.

Value

An IMU vector of the same length as x, with each burst transformed by the corresponding calibration.

Details

An acc_calibration object may contain missing (NA) elements (e.g. if produced by as_acc_calibration()). transform_imu() returns NA in such cases and emits a warning if any bursts are lost because of missing calibration specifications.

If an acc_calibration only has calibration parameters for certain axes (e.g. offset_x = 2048 and slope_x = 0.001), then only those axes will be transformed by transform_imu(). Values for other axes will be converted to NA. The dimension of the input burst matrices therefore remains the same.

See also

acc_calibration() to construct an accelerometer calibration.

Examples

a <- acc_example()

# Transform values using the standard Ornitela calibration formula
transform_imu(a, acc_calibration("ornitela"))
#> <acceleration[2]>
#> [1] (0.01 0 0.01) [m/s^2]  (0 -0.01 0.01) [m/s^2]
#> # frequency: 20 [Hz]

# Transform values using a set of custom acc calibrations.
# Calibrations will be mapped to the input IMU vector by index.
transform_imu(
  a,
  acc_calibration(offset = c(2048, 2046), slope = c(0.001, 0.002))
)
#> <acceleration[2]>
#> [1] (-20.08 -20.08 -20.07) [m/s^2] (-40.13 -40.14 -40.11) [m/s^2]
#> # frequency: 20 [Hz]