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PRH Variables

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Will Gough edited this page Nov 11, 2025 · 3 revisions

The "Pitch-Roll-Heading" file (".mat") generated by this toolkit contains multiple variables that can be useful in a variety of analysis.

PRH Variables:

  • At - The tri-axial accelerometer data in the "tag" frame of reference. This means that "forward" in the data is looking straight through the front of the tag, regardless of the animal's orientation
  • audon - A series of boolean values showing when the hydrophone/audio is recording (1s for Yes) or not recording (0s for No).
  • Aw - The tri-axial accelerometer data in the "whale" frame of reference. This means that "forward" in the data is looking straight through the head of the animal, regardless of the tag's orientation.
  • camon - A series of boolean values showing when the camera is recording (1s for Yes) or not recording (0s for No).
  • DN - The Matlab "Date Numbers" corresponding to time at each data position. Can be converted into a string to visualize time in DD:MM:YYYY HH:MM:SS.fff format, or similar.
  • flownoise - The cumulative reading from the hydrophone/audio (if the tag has acoustics) at a given time. Regressed against Orientation-Corrected Depth Rate during data processing as one method to estimate swimming speed.
  • fs - The sampling rate of the tag deployment. In the example given above, a sample rate of 10 means that there are 10 data points per second. So a deployment length of 89283 samples corresponds to 8928.3 seconds, or 2.48 hours.
  • geoPtrack - The geo-referenced pseudo-track of movement throughout the deployment. Using the orientation and speed of the animal, a pseudo-track is created during data processing (the ptrack variable below). This track can be "geo-referenced" by adding in GPS data - either from the on-board GPS sensor or from external measurements (i.e., a mid-deployment UAS-drone position or the tag recovery position, if found within ~15 minutes of falling off animal).
  • GPS - Any GPS data positions (latitude and longitude coordinates) within the deployment, taken from on-board sensors or external measurements.
  • GPSerr - Any error values associated with GPS data positions.
  • Gt - The tri-axial gyroscope data in the "tag" frame of reference.
  • Gw - The tri-axial gyroscope data in the "whale" frame of reference.
  • head - The heading data, given in radians.
  • INFO - A structure designed to provide metadata about the deployment. These variables are detailed below.
  • JigRMS - The root-mean-squared "jiggle" estimate, essentially the amount of fine-scale movement in the tri-axial accelerometer data measured at high sample rates (typically ≥200Hz). Similar to the flownoise variable, the tag "jiggle" is regressed against Orientation-Corrected Depth Rate during data processing as one method to estimate swimming speed.
  • Light - The amount of light, measured in lumens by the tag's light sensor.
  • Mt - The tri-axial magnetometer data in the "tag" frame of reference.
  • Mw - The tri-axial magnetometer data in the "tag" frame of reference.
  • p - The depth of the animal, measured in meters by the tag's pressure sensor.
  • pitch - The pitch data, given in radians.
  • Ptrack - The unreferenced pseudo-track of movement throughout the deployment, based solely on orientation and speed.
  • roll - The roll data, given in radians.
  • speed - A useful table with multiple speed-related measurements, including the JigRMS and flownoise datastreams. The most commonly used column (JJ) corresponds to the jiggle estimate of swimming speed.
  • speedstats - Information related to the swimming speed estimation models generated during data processing.
  • T - The temperature data, given in degrees celsius, and measured by the tag's temperature sensor. On older model tags, this sensor only measured the tag's internal temperature, whereas newer models measure the external water temperature.
  • tagon - A series of boolean values showing when the tag is attached to the animal (1s for Yes) or not (0s for No).
  • viddeploy The numbers corresponding to each video that occur during the animal-attached portion of the deployment. For example, if the raw tag data contains two full videos before deployment, then viddeploy will start at 3.
  • vidDN - The Matlab "Date Numbers" corresponding to the start times of each video in -viddeploy-.
  • vidDurs - The length of each video in viddeploy, measured in seconds. So the first video in the example above would be 2.1455e+03 seconds (2145.5 seconds), which is equal to 35.75 minutes.
  • vidNam - The filenames for each video in viddeploy.

INFO Sub-Variables:

  • magfield - This includes the total magnetic field strength (b), the inclination (inc), and the declination (dec).
  • whaleName - The unique identifier of the deployment. A broadly used format is to use the genus-species code ("gm" for Globicephalus macrorhynchus), followed by the date of the deployment (YYMMDD - 240409 in this example), followed by the unique ID number of the tag ("J4" in this example). The result is "gm240409-J4".
  • tagnum - The unique ID number of the tag, typically two numbers or a letter followed by 1-2 numbers.
  • notes - Any important notes on the PRH creation process. Typically incorporated during the late stages of data processing.
  • timedif - Used to denote any shift between tag time and "real" time. For example, if the time zone of the computer was wrong during tag setup.
  • CAL - Calibration information for the accelerometer, gyroscope, and magnetometer data.
  • W - The transformation matrix used to switch between the "tag" and "whale" frames of reference. There should be nine values - one for each of the three axes of the accelerometer, gyroscope, and magnetometer data.
  • tagprh - This captures the static offsets (how the tag was stuck on: nose-up/down, rolled, twisted) for each segment of data between tag slips.
  • calperiod - The Matlab "Data Numbers" associated with each calibration period (between two tag slips).
  • calperiodI - The data indices associated with each calibration period (between two tag slips).
  • Wchange - This marks transition points between periods of stable tag orientation. When the tag slips, the calibration changes, and a new W (rotation matrix) is computed for the next segment.
  • tagslip - The data indices associated with each tag slip position.
  • vid4K - A switch (1 for Yes, 0 for No) used to determine if the tag data was processed using the newer "4K" rules. The name is based on a series of CATS tags that were used extensively during ~2021-2024. Multiple datastreams (including the video, if available) are processed differently using the "4K" rules versus the older "Wireless" rules.
  • TempInternal - The internal temperature of the tag, measured in degrees Celsius.
  • UTC - The UTC (Universal Time Code) offset for the location where the tag was deployed. For example, -10 would be Hawaii, while California would be -7 or -8, depending on the time of year (PDT vs. PST, respectively).
  • prhcreated - The date that the PRH file was created
  • creator - The initials of the PRH file creator.
  • Hzs - A structure that includes the sampling rates of each sensor. These include the accelerometer (accHz), gyroscope (gyrHz), magnetometer (magHz), pressure/depth (pHz), light (lHz), GPS (GPSHz), and Temperature (THz and T1Hz).
  • GPSoffset - This gives the time offset (in seconds) between the tag’s internal clock and any GPS timestamps.
  • aud - The Matlab "Data Number" corresponding to the start of the audio datastream, if available.

General Introductions

Preparing CATS Tags

Initial Processing Steps

Creating PRH File

PRH Extras

Fieldwork Tips

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