Measuring Tree Height With a Two-Satellite Constellation

Caitlin Dempsey

Updated:

Recent research has been published in IEEE Xplore on efforts to accurately measure tree height using synthetic aperture radar (SAR) data collected SAOCOM-1. The SAOCOM-1 constellation, composed of two satellites, was launched by the Argentine space agency, known as Comisión Nacional de Actividades Espaciales (CONAE).

The research team, including Santiago Seppi from CONAE, Carlos López-Martínez from the Polytechnic University of Catalonia, and Jacqueline Joseau from Argentina’s National University of Cordoba, used the novel approach of analyzing remotely-sensed data from the SAOCOM satellite constellation to determine height of forest canopies in Corrientes, Argentina. Corrientes is a key region for forest production in Argentina, mainly cultivating pine and eucalyptus trees.

According to the European Space Agency, this marks the first time that a two-satellite constellation has been used to map out tree canopies.

Polarimetric SAR Interferometry (PolInSAR)

To measure forest canopy height, researchers used a series of detailed radar images taken over the course of the year 2021, collected every 8 to 16 days. L-Band SAOCOM data was used to create maps that show the height of forest canopies using a method known as Polarimetric SAR Interferometry (PolInSAR).

The study’s lead author explained to ESA the benefit of using this data: “L-band satellite systems are valuable for scientists because they can penetrate thick vegetation, soil and other structures, providing information that shorter wavelength SAR satellites cannot deliver – this impressive capability opens up many avenues of research.”

PolInSAR is a technique that combines radar images taken from different angles and polarizations in order to differentiate between the various types of signals bouncing back from the ground and vegetation within a single spot. This gives scientists the ability to measure how tall and dense the vegetation in a forest might be by analyzing how the radar signals scatter off of different surfaces.

PolInSAR uses a model called RVoG, which simplifies the forest into two layers: one for the ground and one for the vegetation above it. To figure out the height of the vegetation, scientists compare the actual radar data they get back with what the RVoG model predicts.

Researchers were able to benchmark their tree height results with ground measurements provided by forest owners and data from NASA’s forest monitoring mission called the Global Ecosystem Dynamics Investigation (GEDI). The research showed that using SAOCOM-1’s radar images for mapping forest heights could be very effective with benchmarking showing good accuracy in the estimations based on the test areas studied.

The findings open up new possibilities for commercial forestry managers, policymakers, and the scientific community to leverage SAOCOM’s unique features for various research and operational applications.

References

Seppi, S., López-Martínez, C., & Joseau, M. J. (2024). An Assessment of SAOCOM L-Band PolInSAR Capabilities For Canopy Height Estimation: A Case Study Over Managed Forests In ArgentinaIEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 10.1109/JSTARS.2024.3363435

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About the author
Caitlin Dempsey
Caitlin Dempsey is the editor of Geography Realm and holds a master's degree in Geography from UCLA as well as a Master of Library and Information Science (MLIS) from SJSU.

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