Lake’s Quality Measured From Space Using “Superhero Vision” Technology

An international team of researchers recently demonstrated “superhero vision,” by utilizing satellite technology that can visualize pollution levels not visible to the human eye. Doing so provides a means of gauging the quality of water from space.

The team is composed of researchers from the University of Leicester and the Hungarian Academy of Science and is led by Professor Heiko Baltzer from the Department of Geography. The team, alongside industrial partners, has made use of MERIS or the Medium Resolution Imaging Spectrometer instrument, a programmable, medium-spectral resolution imaging spectrometer that operates in the solar reflective spectral range.

MERIS is carried by Envisat, along with nine other Earth-observation instruments, and has five cameras that are placed side by side and are fitted with a pushbroom spectrometer. Pushbroom sensors look at a specific area for a longer time and as a result, it can gather more light and it is able to record one line of an image instantaneously. This technology is then able to gather data in fifteen spectral bands that can be selected by ground command. Thus, MERIS is designed in such a way that it can obtain data over Earth whenever illumination conditions are passable.

The instrument’s primary use is to observe the color of the ocean and monitor terrestrial observations. Whereas these methods have been used to study the ocean, it has not been readily available for lakes, particularly shallow ones with complex optical environments.

Lake Balaton in Hungary was the subject location for this particular study. The area is popular with tourists and is exposed to meteorological changes that could lead to accumulation of algae.

According to Professor Baltzer, “Lake Balaton is incredibly important for the Hungarian tourism sector, since on an annual basis up to 1 million tourists are visiting it. It is also home to a large diversity of fish and other species. When water quality samples are taken from a ship it is not only a logistic nightmare, but the data collection costs a lot of money and only provides point measurements, making the estimation on the whole lake level very speculative. The frequent satellite data of MERIS adds a synoptic observation to the study of algal blooms and how they develop.”

Chlorophyll-a, a green substance that can be found in algae, is measured at the Balaton Limnological Institute at Lake Balaton with a research ship. Over a thousand satellite images are being processed at the satellite data analysis center of Airbus Defense and Space in Farnborough for the duration of the research. These images are converted into maps of the green chlorophyll concentration in the water. Then, more than 250 ship-based measurements taken over five years are going to check the quality.

This study with the title ‘Validation of Envisat MERIS Algorithms for Chlorophyll Retrieval in a Large, Turbid and Optically-Complex Shallow Lake,’ has been published in the February edition in the journal Remote Sensing of Environment and is accessible by all.