– Institute of Environmental Science, start wide-area and high-resolution remote monitoring using optical sensors –
□ The National Institute of Environmental Research, which belongs to the Ministry of Environment, remotely monitors the algal bloom situation using optical sensors (sensors) mounted on satellites, aircraft, and unmanned aerial vehicles (drones).
○ This remote monitoring of green algae increases the frequency of monitoring and expands the spatial range by adding multi-spectral images of Sentinel-2* satellites and hyper-spectral images using unmanned aerial vehicles following the use of hyperspectral images of existing aircraft. .
* A satellite developed and operated by the European Space Agency, which provides multispectral imagery with a spatial resolution of 5m every 20 days
□ The National Academy of Environmental Sciences conducted a 'research for predicting changes in the water environment using remote sensing techniques' last year, using the wavelength that specifies algae in the sentinel-2 satellite image to calculate the chlorophyll-a concentration and the phycocyanin concentration of cyanobacteria. has developed
○ Multispectral images using satellites are information that detects energy reflected or radiated from the surface in a limited wavelength range of about 10 mainly, and is converted into concentration information by establishing a correlation model with green algae.
○ Hyperspectral images using existing aircraft have a high spatial resolution of 2 m, but there is a disadvantage that it is difficult to operate depending on weather conditions.
○ It is expected that more stable algal monitoring will be possible if multi-spectral images from satellites, which are relatively less constrained by weather conditions, are used.
□ In addition, the National Academy of Environmental Sciences has developed a new drone image processing algorithm based on its aerial image processing technology, and started monitoring algae using the drone from the middle of this month for areas requiring detailed monitoring, such as bird warning points and water intake points. .
○ Green algae remote surveillance video is provided within 2 days after filming, and the newly added satellite and drone video can be checked through the water environment geographic information service within the Water Environment Information System from June 6.
□ Kim Yong-seok, head of the Water Environment Research Department of the National Academy of Environmental Sciences, said, “The results of intensive observations in early summer, when there is a concern that algal blooms will occur, will be used to preemptively respond to algal blooms.”
Attachment 1
Information content provided by algae remote monitoring
□ Multi-spectral satellite (Sentinel-2) image application case
□ Hyperspectral aerial imaging application case
Attachment 2
Terminology Explanation
□ Green algae remote monitoring (monitoring)
○ This was developed to compensate for the difficulty in understanding the overall status of algae with algae information measured at major points. The distribution of algae over the entire river is based on information measured by mounting advanced sensors such as satellites, aircraft, and drones. Techniques to inform situation and concentration
□ Sentinel-2 satellite
○ It is an artificial satellite developed and operated by the European Space Agency to carry out the Earth observation mission. It is possible to photograph the same area on the Earth at intervals of about 2 days using two satellites with the same performance. The captured image consists of 5 bands in the visible, near-infrared, and short-wavelength infrared regions, and the spatial resolution of the image differs from 13 to 10 m depending on the band.
□ Hyperspectral
○ In contrast to multi-spectral sensors that detect energy reflected or radiated from the surface in a limited range of wavelengths of around 10, a hyperspectral sensor* detects energy that is continuous, narrow, and radiated from many spectral bands.
* Hyperspectral sensor: Unlike general cameras, the visible light region (400-700 nm) and near-infrared region (700-1,000 nm) wavelength bands are subdivided into hundreds of zones (bands) for observation. One wavelength of radiation can be detected
□ Blue-green algae (藍藻類)
○ In blue-green algae, the pigment for photosynthesis is scattered throughout the cell and, like bacteria, there is no nucleus in the cell, so it is called Cyanobacteria. It photosynthesizes with chlorophyll, a green pigment, and has auxiliary pigments such as carotenoids, phycocyanin, phycoerythrin, and allophycocyanin in addition to chlorophyll. The size is about 1-50 μm, and the largest is about the diameter of a human hair (50-70 μm), and it reproduces asexually or proliferates by spores.
□ Chlorophyll-a
○ One of the types of chlorophyll. It shows the characteristics of the main absorption wavelength bands of 660 nm and 429 nm. It is present in all photosynthetic organisms except bacteria, and chlorophyll-a is most abundant in phytoplankton in the aquatic environment. Therefore, along with chemical components such as total phosphorus, it has been an indicator of eutrophication in water bodies.
□ Phycocyanin pigment
○ A pigment that transmits light energy to chlorophyll a to advance photosynthesis, and is a representative indigo pigment uniquely contained in blue-green algae. It contains allophycocyanin and phycoerythrin along with phycocyanin, called phycobiliprotein