FRM4DRONES-AQUATIC

Advancing Drone-Based Measurements for Satellite Calibration and Validation of Aquatic Reflectance

Why Drones for Aquatic Calibration and Validation?

Unoccupied Aerial Vehicles (UAVs), or drones, have revolutionized environmental monitoring by offering flexible, high-resolution data collection. Unlike traditional fixed platforms like AERONET or HYPERNETS, drones can assess spatial variability around these stations, improving the representativeness of satellite pixel-scale measurements.

They can also perform transects from shorelines to open seas, providing critical data for validating atmospheric correction algorithms, such as adjacency corrections. This comprehensive approach enhances the accuracy and reliability of satellite Calibration and Validation (Cal/Val) processes.

Challenges and the Need for Fiducial Reference Measurements

High-quality Fiducial Reference Measurements (FRM) are essential for satellite product validation. Achieving FRM status for drone data over water involves several challenges such as:

Addressing the high spatial and temporal variability of water bodies
Accurate data processing from digital numbers to aquatic reflectance including corrections for glint effects
Rigorous calibration
Providing robust uncertainty budgets and SI-traceability

FRM4drones-AQUATIC

The FRM4DRONES-AQUATIC project aims to improve the reliability, traceability, and accuracy of drone-based aquatic measurements.

Through a collective community effort, the project seeks to:

Bring together the community involved in drone-based aquatic Cal/Val
Develop and discuss best practices
Advance uncertainty quantification and standardization of protocols

By doing so, FRM4DRONES-AQUATIC paves the way for drones to become a trusted and complementary tool in the satellite validation ecosystem.

Online Workshops

Join our upcoming online workshops - more information below:

Day	Time	Topic	Registration
Wednesday, June 11, 2025	15:00-17:00h CET	Workshop 1: Data Acquisition and Processing Protocols	👉 Register here
TBD	TBD	Workshop 2: Uncertainty, FRM, and Traceability	Stay tuned

Program Workshop 1: Data Acquisition and Processing Protocols (June 11, 2025)

The FRM4DRONES-AQUATIC workshop series brings together the community exploring drone-based approaches for aquatic reflectance measurements. This first online session focuses on data acquisition and processing protocols, showcasing current practices and technical challenges while laying the groundwork for a collaborative roadmap toward standardised, high-quality methodologies.

Introduction – VITO:
Welcome & Introduction to the FRM4DRONES-AQUATIC Workshop: Toward Standardised UAV-Based Aquatic Reflectance

The workshop will open with an introduction to the FRM4DRONES- AQUATIC project, highlighting the motivation behind advancing drone-based aquatic reflectance measurements toward Fiducial Reference Measurement (FRM) standards. The main challenges in aquatic drone Cal/Val will be outlined. We will demonstrate, through selected case studies, the use of the MAPEO-Water processing chain as an example of UAV-based aquatic data processing to address some of these challenges. Finally, the objectives and structure of the workshop will be presented, with an emphasis on community engagement and the roadmap toward standardized protocols.

Anna Windle, Satellite Mission Post-Doctoral Fellow, SSAI (NASA GSFC):
Evaluation of Unoccupied Aircraft System (UAS) Remote Sensing Reflectance Retrievals for Water Quality Monitoring in Coastal Waters

Unoccupied aircraft systems (UAS) equipped with optical sensors offer on-demand, highly resolved data. Aquatic UAS applications are in their infancy, and the critical removal of light reflected directly off the skin of water has received little attention in the literature. This talk will describe several different approaches to remove direct surface reflectance from UAS imagery and evaluate each against in situ Rrs data. Furthermore, DroneWQ, a Python library for measuring water quality with a multispectral drone sensor, will be presented.

Carmen Cillero, Researcher at Estonian University of Life Sciences:
Experimental Set-Up and First Results of Drone-Based Radiometry. Future Needs and Potential for Satellite Cal/Val

This talk will describe the experimental set-up developed to integrate a spectroradiometer Ocean Optics STS on board an octocopter to perform point measurements of Rrs by flying a drone over bodies of water. The experimental set-up was tested in different OWTs and compared to a standard set of TriOs RAMSES Spectroradiometers Rrs measurements. We will explore together the possibilities that this approach may offer in the context of the project FRM4DRONES.

Alejandro Román, PhD in Marine Sciences & Technologies:
Novel Direct Georeferencing-Based Method for Accurate Water Surface Mosaicking with Drone Multispectral Imagery

Unoccupied Aircraft Systems (UAS or drones) enable comprehensive observation of marine systems with high spatial and temporal resolutions. However, water surfaces are optically dynamic, and the absence of fixed features precludes the applicability of common terrestrial photogrammetric mosaicking techniques, thereby limiting the ability to monitor water quality using multispectral technology. This study presents an efficient, precise, and benchmark mosaicking method that directly addresses this limitation. A Python-based georeferencing approach leverages image orientation and associated UAS metadata collected during pre-programmed surveys. The integration of this open-source and intuitive technique, alongside emerging surface reflectance retrieval methods, helps advance UAS monitoring in coastal environments.