| fix_pressure {tagtools} | R Documentation |
Correct a depth or altitude profile
Description
This function is used to correct a depth or altitude profile for offsets caused by miscalibration and temperature. This function finds minima in the dive/altitude profile that are consistent with surfacing/landing. It uses the depth/height at these points to fit a temperature regression.
Usage
fix_pressure(p, t, sampling_rate, maxp = NULL)
Arguments
p |
A sensor list or vector of depth/altitude in meters |
t |
A sensor list or vector of temperature in degrees Celsius |
sampling_rate |
The sampling_rate of p and t in Hz. This is only needed if p and t are not sensor lists. The depth and temperature must both have the same sampling rate (use 'decdc' if needed to achieve this). |
maxp |
The maximum depth or altitude reading in the pressure data for which the animal could actually be at the surface. This is a rough measurement of the potential error in the pressure data. The unit is meters. Start with a small value, e.g., 2m and rerun fix_pressure with a larger value if there are still obvious temperature-related errors in the resulting depth/altitude profile. |
Value
A list with 2 elements:
p: A sensor list or vector of corrected depth/altitude measurements at the same sampling rate as the input data. If the input is a sensor list, the output will also be.
pc: A list containing the pressure offset and temperature correction coefficients. It has fields: pc$tref which is the temperature compensation polynomial. This is used within the function to correct pressure as follows: p + stats::polyval(pc$tcomp, t - pc$tref).
Note
This function makes a number of assumptions about the depth/altitude data and about the behaviour of animals: First, the depth data should have few incorrect outlier (negative) values that fall well beyond the surface. These can be reduced using median_filter.m before calling fix_depth. Second, the animal is assumed to be near the surface at least 2