Author: ligiadmin

This is the first publication partially funded by the European Space Agency’s HyperBOOST project. With collaboration from scientists at Plymouth Marine Laboratory, UK and the Marine and Environmental Science Centre, Faculdade de Ciências da Universidade de Lisboa, Lisboa, Portugal.

The study consists of deployments at three different water bodies (Western English Channel – UK, Tagus Estuary – Portugal, Lake Balaton – Hungary). In each case, a So-Rad system was mounted onboard a ship-of-opportunity undergoing operational tasks whilst capturing radiometric data and ship transects.

Abstract

Validation of satellite-derived aquatic reflectance involves relating meter-scale in situ observations to satellite pixels with typical spatial resolution ∼ 10–100 m within a temporal “match-up window” of an overpass. Due to sub-pixel variation these discrepancies in measurement scale are a source of uncertainty in the validation result. Additionally, validation protocols and statistics do not normally account for spatial autocorrelation when pairing in situ data from moving platforms with satellite pixels. Here, using high-frequency autonomous mobile radiometers deployed on ships, we characterize the spatial structure of in situ R_rs in inland and coastal waters (Lake Balaton, Western English Channel, Tagus Estuary). Using variogram analysis, we partition R_rs variability into spatial and intrinsic (non-spatial) components. We then demonstrate the capacity of mobile radiometers to spatially sample in situ R_rs within a temporal window broadly representative of satellite validation and provide spatial statistics to aid satellite validation practice. At a length scale typical of a medium resolution sensor (300 m) between 5% and 35% (median values across spectral bands and deployments) of the variation in in situ R_rs was due to spatial separation. This result illustrates the extent to which mobile radiometers can reduce validation uncertainty due to spatial discrepancy via sub-pixel sampling. The length scale at which in situ R_rs became spatially decorrelated ranged from ∼ 100–1,000 m. This information serves as a guideline for selection of spatially independent in situ R_rs when matching with a satellite image, emphasizing the need for either downsampling or using modified statistics when selecting data to validate high resolution sensors (sub 100 m pixel size).

Read the full publication on the Frontiers in Remote Sensing website

Reference

Jordan, TM, Simis, SGH, Selmes, N, Sent, G, Ienna, F and Martinez-Vicente, V. 2023. Spatial structure of in situ reflectance in coastal and inland waters: implications for satellite validation. Frontiers in Remote Sensing, 4. https://doi.org/10.3389/frsen.2023.1249521

To ensure the promotion of Equity, Diversity and Inclusion, the work experience was offered to a selection of local schools from varying social backgrounds. Gender diversity was also important to promote careers in STEM (Science, Technology, Engineering and Mathematics) for women.

Students worked in teams to learn what the daily work of marine scientist looks like in real life. The teams then worked on projects relating to satellite remote sensing, microplastics and mathematical modelling, which were presented to their peers at the end of the week.

Activities included: an interactive tour of the laboratory; a visit to the Plymouth Marine Laboratory (PML) research vessel, Plymouth Quest; talks on marine science topics and career paths, and hands-on tasks, such as measuring changes in water colour for use in optical analysis.

Above: Students in the laboratory with HyperBOOST PI Dr Victor Martinez-Vicente and Dr Tom Jordan as they demonstrate the changes in optics using a sensor and a large container of seawater.

Exploring “Nexus Island”

There was also a fun activity where students played the “Nexus Island” game. This game-based teaching resource was developed by EMBL and inspired by the TRaversing European Coastlines (TREC) expedition.
It was an ideal opporunity for the students to interact with each other and explore the connections within ecosystems as they explored the four quadrants of the island.



Dr Victor Martinez-Vicente, co-ordinator of the experience and HyperBOOST PI, commented:

“Sharing my passion about ocean science and being surprised by the insights from the students have made the work experience week one of the most enjoyable activities this year. I wanted to organise the work experience to give local young people the opportunity to know first-hand what it really means to be a marine scientist so that they can have a good picture before they make those important choices on their degrees the following year. I also wanted to give the opportunity to people working at PML to do something different in their day-to-day work and interact with students.”

“My reward was to hear that I might have helped inspired some of the participants to consider marine science as a career. It was great to see students passionately engaging to solve practical issues and working in teams to find creative solutions to unexpected problems. It took me by surprise how they quickly covered the equipment with their own lab coats when a sudden spell of rain risked on damaging the equipment, and also their resilience when the rain persisted and they did not give up. But then, I come from the south of Spain and I’m still not used to the British rain, even after 20 years!”

Student feedback

The week’s work experience was an intitial pilot and due to its success aims to be repeated in 2024. You can read the positive feedback from the students below:

“Thank you so much for your guidance and kindness throughout this week. I have thoroughly enjoyed working with you and it’s people like you, in your line of work that really inspire me to pursue this.”

“Thanks for putting together an interesting and enjoyable week!”

“Thank you for the work experience, it was an incredible week and we loved it.”

“Thanks you for all your help and effort in arranging this experience for us. I’m very honoured to have been a part of this pilot and I hope future attendees will enjoy it as much as I have”

 

Related information

View more information about the “Nexus Island” game-based teaching resource and download the resources on the EMBL website

In late June the HyperBOOST (Hyperspectral Bio-Optical Observations sailing on Tara) team held the initial ‘kick-off’ meeting for the project.

The two-year project utilisizes the EMBL Trec expedition to provide a means to gather a variety of in situ data for the validation of satellite data.HyperBOOST is a continuation from the BiCOME (Biodiversity of the Coastal Ocean: Monitoring with Earth Observation) project. BiCOME is one of three projects that form part of the European Space Agency ‘Biodiversity+ Precursors’ which focus research on Terrestrial, Freshwater and Coastal Ecosystems respectively.

Coastal waters can be difficult to monitor due to their optical complexity, and with Biodiversity facing a huge number of challenges as the climate changes, it is therefore vital to advance our understanding and assist with the development of Earth Observation technology and in situ observations.

The European Space Agency (ESA) funded project is led by a team at Plymouth Marine Laboratory, working with partners from EMBL, CNR, LOV and the University of Maine.

Working collaboratively with the European Molecular Biology Laboratory (EMBL) and the TREC (Traversing European Coastlines) project.

Updates in the form of news, data and publications will be added to the HyperBOOST website as the project progresses.