About CalVal Portal

The European Space Agency (ESA) is providing information and data for Calibration (Cal) and Validation (Val) of Earth Observation (EO) data through this portal.

The Web Portal provides:

  • Description of methodologies
  • Description of instrument characteristics
  • Access to instrument meta data
  • Access to EO data over internationally agreed sites
  • Access to in-situ data
  • Access to calibration software

Currently the Portal is dedicated to calibration of Infrared and Visible Optical Sensors (IVOS). It will extended to other instruments as well as to validation in future releases.

Efficient use of EO data relies on multi source data access, interoperability, long-term data preservation, and definition standards. Calibration and validation are two essential steps for the correct use and understanding of the EO data. Specifically, applications in the GMES context are based on multi sources data and can be addressed only if the calibration and validation process is well defined and controlled through common standards. GMES requires the use of fusion of similar sensor data to guarantee the sustainability of the services. The CalValPortal is dedictaed to ease and strengthen the calibration process and therefore will increase the comparability of similar instruments data.

On the background of these requirements for sensor calibration, intercalibration and product validation, the subgroup on Calibration and Validation of the Committee on Earth Observing System (CEOS) formulated the following recommendation during the plenary session held in China at the end of 2004, with the goal of setting-up and operating an internet based system to provide sensor data, protocols and guidelines for these purposes:

  • Background:
    Reference Datasets are required to support the understanding of climate change and quality assure operational services by Earth Observing satellites. The data from different sensors and the resulting synergistic data products require a high level of accuracy that can only be obtained through continuous traceable calibration and validation activities.
  • Requirement:
    Initiate an activity to document a reference methodology to predict Top of Atmosphere (TOA) radiance for which currently flying and planned wide swath sensors can be intercompared, i.e. define a standard for traceability. Also create and maintain a fully accessible web page containing, on an instrument basis, links to all instrument characteristics needed for intercomparisons as specified above, ideally in a common format. In addition, create and maintain a database (e.g. SADE) of instrument data for specific vicarious calibration sites, including site characteristics, in a common format. Each agency is responsible for providing data for their instruments in this common format. Recommendation : The required activities described above should be supported for an implementation period of two years and a maintenance period over two subsequent years. The CEOS should encourage a member agency to accept the lead role in supporting this activity. CEOS should request all member agencies to support this activity by providing appropriate information and data in a timely manner.

This system shall, therefore, support worldwide activities on calibration and validation, and specifically ensure that sensor intercalibration is favoured in a standardised way. The overall goal is, therefore, to increase measurement accuracy of all the sensors which will be supported by this system, and this so that GMES can be served with the best information products regardless of the sensor providing the source measurements.