Sensors: Acceleration Viewport

Acceleration Panel

The acceleration panel provides an overview of burst level data with options to

  • zoom into your dataset
  • quickly jump to specific timestamps
  • select regions of interest (shift left-drag)

Bursts

Modern tags capture acceleration data along with location data. As opposed to GPS data, acceleration data is often captured as bursts (see burst vs. continuous). A burst is a consecutive array of measurements starting at a specific timestamp. These measurements do not necessarily align to a known GPS position as they are often recorded following a predefined schedule of fixed intervals. Acceleration data often covers x, y and z acceleration, quite similar to common smartphones.

Firetail can visualize bursts and synchronizes the replay with matching GPS measurements.

Furthermore, Firetail enables the annotation of user-defined labels to selected bursts (see Section Burst annotation).

Loading acceleration data

Downloading data with associated bursts can be done using Firetail’s integrated Movebank download. Here we show experimental data from the Galapagos Albatrosses study (ID: 2911040), tag 131.

burst data The screenshot above shows a number of bursts selected and highlighted in the map window.

Firetail supports

  • e-obs type burst data
  • continuous acceleration alongside with GPS fixes, e.g. TechnoSmart and Ornitela
  • continuous acceleration as accessory measurements, e.g. Vectronic data.
  • compatible movebank files

Contact us if your tag does not work as expected. We’re glad to receive your feedback!

Activity Plots

Activity plots provide a fast overview of individual activities over time. Darker areas encode more active phases.

For burst data, you can generate an activity plot for a tag/individual by using Window > Activity Plot. When acceleration data of multiple individuals is loaded you may choose which individual should be plotted:

activity plot

A sample result would look like this:

activity plot

Activity value of a burst

Let B a burst that consists of n samples capturing acceleration in 3 axes (x, y, z).

The vectors

\(x := (x_1, \dots, x_n)\newline y := (y_1, \dots, y_n)\newline z := (z_1, \dots, z_n)\)

represent the respective axis of ordered sample values in B.

The activity value \(\text{act}(B)\) is then defined as

\(\text{act}(B) := \frac{1}{3*(n-1)} \sum_{d \in \{x,y,z\}} \sum_{i=2}^{n} |d_{i-1}-d_{i}|\)

Selecting a burst region

Selecting one or multiple bursts can be done using either by

  1. a shift-left mouse button selection on the map or the acceleration data window
  2. add more intervals using ctrl-shift-left mouse button on the map or acceleration data window

Deselect a region by a single click or drag an empty box in the map.

burst data

Selecting a burst region via threshold

You can use thresholds on event data to select all regions that exceed this threshold (speed, satellite count, …). Use Ctrl-drag in the event data window to select all regions that exceed the shown threshold.

Use the control

  • <= to select regions below the threshold and
  • > to select regions above the threshold

Burst annotation

Firetail offers a range of tools to annotate (burst level) acceleration data with categories and layers.

Important:

Currently, Firetail does not autosave annotations. Use File > Save Annotations after important changes to store your annotations alongside your project on your local hard drive (You will be asked to save changes before closing a project though).

Note that this option is enabled when data is downloaded the Download Movebank by … menu entries.

We discuss the details in Section Burst Annotation.

Annotations are managed locally and therefore require a project to be loaded via the File > Download Movebank by... menu entries. Multi-animal studies can be annotated per tag/individual or deployment.

The most reliable granularity for annotation is the deployment level.

Why deployments?

  • Tags can swap individuals
  • Individuals swap tags
  • Deployments are same tag/same individual

Save/Export Data and Annotations

Note that only the option Export Annotations will produce a format that Firetail can re-import. See save/load acceleration categories.

Firetail offers several ways to export annotated data as comma separated values (CSV).

  1. Select one of the options in File > Annotations > Export (...) as CSV
  2. Choose one of the available options explained below

export annotations

Note: if no annotations are available in the current project, exported files will be empty

Save Annotations

This will save the annotations along with the downloaded movebank data. This will preserve your annotations across multiple Firetail sessions (restarts).

ACC bursts as CSV

This option will export acc bursts, together with your annotations.

save annotations

You’ll be asked whether to include raw burst data or the timestamp only. In the first case, the bursts data will be added to the respective burst.

To better understand the difference, see this diff-view of both options:

diff annotations

ACC samples as CSV

This option will export acc data as samples, together with your annotations.

GPS as CSV

This will export the annotated region as separate track.

Glossary

For technical terms please refer to the incredibly complete Movebank Glossary.