Dual-Band Lidar System Used to Study Insect Activity in a Tropical Cloud Forest

Researchers at the Departmento de Física of the Escuela Politécnica Nacional in Quito, Ecuador, have implemented an entomological dual-band 808 and 980-nm light detection and ranging (lidar) system to study insect activity in a tropical cloud forest, and the results were recently published in Applied Spectroscopy (1). The system was successfully tested at a sample rate of 5 kHz during challenging foggy conditions, with backscattered signals retrieved from a distance of up to 2.929 km. The study focused on fog aspects, potentials, and benefits of such dual-band systems, and demonstrated that the modulation contrast between insects and fog is high in the frequency domain, allowing for better identification and quantification in misty forests.

Enchanted tropical rain forest | Image Credit: © Ricardo Nóbrega - stock.adobe.com

The dual-band infrared (IR) Scheimpflug lidar system is a remote sensing tool that uses two different wavelengths of light (808 and 980 nm) to detect and measure insect activity in a tropical cloud forest. This system emits a laser beam which bounces off of objects in its path, and the backscattered signal is captured by a detector. By analyzing the characteristics of the backscattered signal, such as intensity, frequency, and pixel spread, the system can identify and quantify insect and bat activity in the forest.

The Scheimpflug design of the lidar system allows it to maintain focus over a large depth of field, making it well-suited for studying activity in a forest environment where the beam may encounter obstructions at different distances from the lidar. The use of dual-band IR light allows for better identification and quantification of insect activity in misty forests, where the contrast between insects and fog is higher in the frequency domain compared to the time domain. Overall, the dual-band IR Scheimpflug lidar system is a powerful tool for studying and monitoring insect and bat activity in tropical cloud forests, and it could have important implications for biodiversity conservation efforts.

The study also showed oscillatory lidar extinction effects caused by the combination of dense fog and large moths partially obstructing the beam. Researchers were able to identify the dorsal and ventral sides of moth wings by estimating the corresponding melanization with the dual-band lidar. In addition, they demonstrated that the wing beat trajectories in the dual-band parameter space are complementary, rather than covarying or redundant, making a dual-band entomological lidar approach to biodiversity studies feasible in situ and endowing species specificity differentiation.

The findings of this study, published in Applied Spectroscopy, demonstrate the potential of dual-band lidar systems to monitor, understand, and safeguard the biological resources of one of the most biodiverse countries on Earth (1). Future improvements are discussed, indicating the introduction of these methodologies is a significant step towards biodiversity conservation.

Reference

(1) Santos, V.; Costa-Vera, C.; Rivera-Parra, P.; Burneo, S.; Molina, J.; Encalada, D.; Salvador, J.; Brydegaard, M. Dual-Band Infrared Scheimpflug Lidar Reveals Insect Activity in a Tropical Cloud Forest. Appl. Spectrosc. 2023, ASAP. DOI: 10.1177/00037028231169302