DOI: 10.5061/dryad.3ffbg79t3
title: Tracking small animals in complex landscapes: a comparison of localisation workflows for automated radio telemetry systems

description: Automated radio telemetry systems (ARTS) have the potential to
 revolutionise our understanding of animal movement by providing a
 near-continuous record of individual locations in the wild. However,
 localisation error in ARTS data can be very high, especially in natural
 landscapes with complex vegetation structure and topography. This curtails
 the research questions that may be addressed with this technology. We set
 up an ARTS grid in a valley with heterogeneous vegetation cover in the
 Colombian high Andes and applied an analytical pipeline to test the
 effectiveness of localisation methods. We performed calibration trials to
 simulate animal movement in high- or low-flight, or walking on the ground,
 and compared workflows with varying decisions related to signal cleaning,
 selection, smoothing, and interpretation, along with four multilateration
 approaches. We also quantified the influence of spatial features on the
 system’s accuracy. Results showed large variation in localisation error,
 ranging between 0.4–43.4 m and 474–1929 m, depending on the localisation
 method used. We found that the selection of higher radio signal strengths
 and data smoothing based on the temporal autocorrelation are useful tools
 to improve accuracy. Moreover, terrain ruggedness, height of movement,
 vegetation type, and the location of animals inside or outside the grid
 area influence localisation error. In the case of our study system,
 thousands of location points were successfully estimated for two
 high-altitude hummingbird species that previously lacked movement data.
 Our case study on hummingbirds suggests ARTS grids can be used to estimate
 small animals’ home ranges, associations with vegetation types, and
 seasonality in occurrence. We present a comparative localisation pipeline,
 highlighting the variety of possible decisions while processing radio
 signal data. Overall, this study provides guidance to improve the
 resolution of location estimates, broadening the application of this
 tracking technology in the study of the spatial ecology of wild
 populations.
description: # Tracking small animals in complex landscapes: a comparison of
 localisation workflows for automated radio telemetry systems
 [https://doi.org/10.5061/dryad.3ffbg79t3](https://doi.org/10.5061/dryad.3ffbg79t3) ## Description of the data and file structure This dataset includes all data and necessary code in R scripts to produce the results of the associated paper. ### Files and variables #### File: tags\_id.csv **Description:** Table with information of tags deployment on hummingbirds. ##### Variables * tag_id: Unique identifier for tags * tag_type: Type of tag, LifeTag or PowerTag * tag_attachment_method: Tag attachment method, harness or glue-on * attached: Whether tag has been deployed on an animal or not * date_m_d_y: Date of tag deployment, in month, day and year * species: Latin name of species tag was deployed on * id: Unique identifier for individual in color code * hour: Time of tag deployment #### File: Nodes.csv **Description:** Table with information on node location. ##### Variables * Own_NodeId: Own unique node identifier * NodeId: Manufacturer's unique node identifier * Latitude: Latitude in decimal degrees * Longitude: Longitude in decimal degrees * NodeUTMx: UTM longitudinal location, projected EPSG * NodeUTMy: UTM latitudinal location, projected EPSG #### File: time\_diff\_matched\_df.csv **Description:** Table with matched signal strength values for tags used in calibration trials. ##### Variables * TagId: Unique identifier for tags * Time.local: Time in GMT * NodeId: Manufacturer's unique node identifier * TagRSSI: Signal strength measured in decibels * time_format: Formatted time to switch to local time * node_local_time: Local time * unique_trial_id: Unique identifier for calibration trial * lon: Longitude in decimal degrees * lat: Latitude in decimal degrees * elevation: Altitude in metres above sea level * test_height: Height of calibration trial, either ground (low), mid or drone (high) * test_local_time: Local time of start of calibration trial * tag_type: Type of tag, LifeTag or PowerTag * start_time: Start time of calibration trial * end_time: End time of calibration trial * reloc_id: Unique identifier to location estimate * time_difference: Difference in time between beep data from radio signal and measured time in calibration trial (measured in seconds) * abs_time_difference: Correction of time difference for absolute values (measured in seconds) #### File: beep\_data.zip **Description:** Compressed folder with radio signal strength reads during the time that hummingbirds flew over the grid. ## Code/software All analyses were carried out using R. The following files for R scripts are included: 1.decay_function.R: Calculate exponential decay function from calibration data 2.nls_multilateration.R: Estimate locations through different multilateration options 3.error_analyses.R: Calculate error in metres of estimates to known locations 4.hummer*_*rss_to_tracks.R: Convert signal reads to movement tracks for tracked hummingbirds 5.Second_smoothing_after_multilat.R: Smoothing options after multilateration 6.Smoothing_rss_before_multilat.R: Smoothing options before multilateration ## Access information Other publicly accessible locations of the data: * Data on ground elevation was obtained from the GLO-30 Copernicus digital elevation model (30 m resolution) of the European Space Agency (ESA, 2024).