Airborne S-band SAR for forest biophysical retrieval in temperate mixed forests of the UK

Ramesh K. Ningthoujam, Heiko Balzter, Kevin Tansey, Keith Morrison, Sarah C.M. Johnson, France Gerard, Charles George, Yadvinder Malhi, Geoff Burbidge, Sam Doody, Nick Veck, Gary M. Llewellyn, Thomas Blythe, Pedro Rodriguez-Veiga, Sybrand van Beijma, Bernard Spies, Chloe Barnes, Marc Padilla-Parellada, James E.M. Wheeler, Valentin LouisTom Potter, Alexander Edwards-Smith, Jaime Polo Bermejo

Research output: Contribution to journalArticleScientificpeer-review

17 Citations (Scopus)
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Abstract

Radar backscatter from forest canopies is related to forest cover, canopy structure and aboveground biomass (AGB). The S-band frequency (3.1-3.3 GHz) lies between the longer L-band (1-2 GHz) and the shorter C-band (5-6 GHz) and has been insufficiently studied for forest applications due to limited data availability. In anticipation of the British built NovaSAR-S satellite mission, this study evaluates the benefits of polarimetric S-band SAR for forest biophysical properties. To understand the scattering mechanisms in forest canopies at S-band the Michigan Microwave Canopy Scattering (MIMICS-I) radiative transfer model was used. S-band backscatter was found to have high sensitivity to the forest canopy characteristics across all polarisations and incidence angles. This sensitivity originates from ground/trunk interaction as the dominant scattering mechanism related to broadleaved species for co-polarised mode and specific incidence angles. The study was carried out in the temperate mixed forest at Savernake Forest and Wytham Woods in southern England, where airborne S-band SAR imagery and field data are available from the recent AirSAR campaign. Field data from the test sites revealed wide ranges of forest parameters, including average canopy height (6-23 m), diameter at breast-height (7-42 cm), basal area (0.2-56 m2/ha), stem density (20-350 trees/ha) and woody biomass density (31-520 t/ha). S-band backscatter-biomass relationships suggest increasing backscatter sensitivity to forest AGB with least error between 90.63 and 99.39 t/ha and coefficient of determination (r2) between 0.42 and 0.47 for the co-polarised channel at 0.25 ha resolution. The conclusion is that S-band SAR data such as from NovaSAR-S is suitable for monitoring forest aboveground biomass less than 100 t/ha at 25 m resolution in low to medium incidence angle range.

Original languageEnglish
Article number609
JournalRemote Sensing
Volume8
Issue number7
DOIs
Publication statusPublished - 1 Jul 2016

Keywords

  • Aboveground biomass
  • MIMICS-I model
  • S-band SAR
  • Savernake Forest
  • Wytham Woods

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