Keeping carbon stocks in check

Satellite radar data are being used to map Earth’s vital resources. The latest advances and applications of the POLinSAR remote sensing technique were highlighted at a conference held last week.

Polarimetric InSAR – or POLinSAR – is a remote sensing technique based on polarimetric information in Synthetic Aperture Radar (SAR) images.

With this technique, a radar sends polarised pulses towards the target, and the information in the signals backscattered from Earth can be used to infer properties of the target area, such as the 3D structure of a forested area.

By deriving information on the structure, forest biomass can be estimated. Accurately estimated forest biomass and its distribution is a key parameter for forest inventories and vegetation modelling.

Since forests assist in removing carbon dioxide from the atmosphere, mapping forest biomass is important for our understanding the global carbon cycle.

Biomass inventories are required by the UN and Intergovernmental Panel on Climate Change to provide a comprehensive analysis on estimates of terrestrial carbon fluxes for climate change reports.

In Estonia, forests cover about half of the land. To improve the country’s greenhouse gas inventory and the understanding of the carbon balance in the country, the cooperative Regio PECS project between Estonia and ESA (as part of the Plan for European Cooperating States) was established.

Through Regio PECS, satellite data are being exploited to map forest biomass density and estimate forest value.

The work is also a first step in long-term forest monitoring, and provides a more sophisticated calculation of the country’s carbon stocks.

This and other applications of the remote sensing technique were recently presented at the 2013 POLinSAR workshop, held last week at ESA’s ESRIN establishment in Frascati, Italy.

To demonstrate the importance and the unique benefits of this technique for a wide range of remote sensing applications beyond mapping biomass, ESA has initiated an application study called PolSAR-Ap. Led by the DLR German Aerospace Center, the project involves expert groups from European institutes and universities.

Scientists working on PolSAR-Ap have developed pertinent applications such as the monitoring of water extent in wetlands, the distribution of floods, 3D imaging of urban areas, the detection of oil slicks from space and the classification of ice types in polar regions.

“PolSAR-Ap consistently gathers a diverse selection of applications that are sorted into five themes, and demonstrates their applicability on current available satellite data,” said the project’s leader, Irena Hajnsek.

“The initiative is unique as it brings all state of the art applications together and provides the tools needed by the science community.”

The next big meeting that will provide an opportunity to discuss progress in the field of POLinSAR will be the Living Planet Symposium, schedule for 9-13 September in Edinburgh, UK.

For more information on ESA’s largest scientific event of the year, visit the symposium website.