As part of the SITES Water monitoring program, floating chambers are used to determine greenhouse gas (GHG) emissions of carbon dioxide (CO2) and methane (CH4) from lakes. The GHG program is conducted at five stations (Abisko, Asa, Erken, Skogaryd and Svartberget) and runs throughout the open water season. The sampling strategy, three transects each with four chambers spread across a depth interval, is based on the lake depth structure and is individual for the different stations. Since the lakes are spread across different climate gradients, the open water season varies, with lakes located in southern Sweden able to start the program earlier in the year.   

As part of SITES Spectral, the SITES stations operate drones in the form of small helicopters, equipped with RGB and multispectral cameras.

RGB cameras are useful for mapping the ground in natural colors in 3-D. Multispectral cameras record images in several wavelengths, including near-infrared, and are useful for monitoring vegetation conditions. Depending on camera type and flying conditions, data need to be calibrated to provide accurate data for quantifying vegetation amount.

Per-Ola Olsson, researcher at Lund University, and collaborators have carried out an analysis of errors related to calibration, and developed a methodology for calibration that minimizes variations related to incoming light fluctuations. The analysis shows that calibration is an important step to be carried out before quantitative analyses of multispectral data from drones.

The results and useful guidelines for how to carry out the calibration were recently published in the open access journal Remote Sensing.

Reference
Olsson, P.-O., A. Vivekar, K. Adler, V. E. Garcia Millan, A. Koc, M. Alamrani & L. Eklundh (2021) Radiometric Correction of Multispectral UAS Images: Evaluating the Accuracy of the Parrot Sequoia Camera and Sunshine Sensor. Remote Sensing, 13, 577.

The AquaNet team, led by the programme coordinator Silke Langenheder, are proud and happy to announce that a detailed description of the SITES AquaNet infrastructure has now been published in Limnology & Oceanography Methods!

SITES AquaNet offers:

1. openness to the scientific community
2. the possibility to use natural lake communities for experiments
3. the possibility to conduct and participate in modularized experiments across time and space
4. high frequency sensor systems
5. expert support by our technical staff and
6. access to data from the accompanying monitoring programme SITES Water.