ThermalTracker-3D: offshore bird and bat monitoring

ThermalTracker-3D is a tool with thermal and visible-light cameras and image recognition software for bird and bat activity monitoring offshore. This system can be deployed on small lidar buoys and has effectively identified and quantified bird and bat activity onshore and offshore. Data from this system can inform offshore wind turbine siting or collision risk models for birds and bats.

Background

The offshore environment is harsh, with limited accessibility for scientists to conduct long-term research. Remote sensing technologies provide an alternative to traditional labor-intensive field studies for collecting animal data. They provide constant data collection, never fatigue, and require minimal maintenance throughout the year. These characteristics make remote sensing technologies, such as ThermalTracker-3D, ideal for collecting offshore bird and bat data.

ThermalTracker-3D system

ThermalTracker-3D is software and hardware technology that generates flight tracks from thermal imagery of birds and bats recorded above the system. Tracks can be identified to species from the visible-light camera when sufficient daylight and enough visible detail are available. This technology is essential to help scientists understand bird and bat flight speeds, flight heights, and flight directions offshore.

The ThermalTracker-3D system was originally designed to quantify bird activity in offshore wind energy areas during pre- and post-construction studies with one camera. The system was eventually updated to include two cameras, which allowed researchers to collect three-dimensional data using stereo-vision processing. A third revision added a visible-light camera, a dedicated computer, and an integrated camera stabilization system (Figure 1).

The combined system can be installed on stationary wind turbine platforms or floating buoys. In cases where the system is mounted to an unstable substrate (e.g., buoys), a camera stabilization system is also installed. The authors used a Perfect Horizon camera stabilization system for this purpose. A satellite modem allows remote system monitoring and thermal tracks to be transferred hourly to shore. Data from the visible-light camera has to be downloaded manually.

Detections

For the offshore test deployment, the study period lasted from May 4, 2021, until August 13, 2021, when the buoy’s generator failed, and ThermalTracker-3D could no longer operate. Despite the abbreviated trial, the offshore test detected 2440 flight tracks, including detections during the nighttime hours (Figure 2). The target detection rate decreased from 89% in the 2015 ThermalTracker-3D study to 52% in the current study. The lower detection rates were likely because the offshore platform motion was absent in the previous terrestrial testing.

Limitations

The main limitations of ThermalTracker-3D are the following:

• Limited detection rates in the offshore environment compared to on land
• Camera motion from the floating platform affected detection rates
• Limited data transmission from the offshore environment
• Manual taxonomic identifications required

Conclusion

The ThermalTracker-3D technology was designed to collect baseline data on bird and bat activity in the offshore environment before a wind farm’s construction. The system was built with off-the-shelf components that cost less than $50,000, excluding labor, setup, and data analysis. Camera motion is the greatest challenge with cameras deployed on offshore buoys, making some images blurry and difficult to interpret. Despite the challenges, the ThermalTracker-3D system successfully identified 2,440 flight tracks during the operational period and could be a useful remote sensing tool for bird and bat research in the offshore environment.

Literature Cited

Matzner, S. V. I. Cullinan, and C. A. Duberstein. 2015. Two-dimensional thermal video analysis of offshore bird and bat flight. Ecological Informatics 30: 20-28. https://doi.org/10.1016/j.ecoinf.2015.09.001.

Matzner, S., T. Warfel, and R. Hull. 2020. ThermalTracker-3D: A thermal stereo vision system for quantifying bird and bat activity at offshore wind energy sites. Ecological Informatics 57. https://doi.org/10.1016/j.ecoinf.2020.101069.

Matzner, S., T. Warfel, R. Hull, and N. Williams. 2022. ThermalTracker-3D offshore validation technical report. Offshore Validation Technical Report, Pacific Northwest National Laboratory. https://tethys.pnnl.gov/publications/thermaltracker-3d-offshore-validation-technical-report.