Vegetation canopy height estimation in dynamic tropical landscapes with TanDEM‐X supported by GEDI data

Michael Schlund*, Arne Wenzel, Nicolò Camarretta, Christian Stiegler, Stefan Erasmi

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

3 Citations (Scopus)
90 Downloads (Pure)

Abstract

Vegetation canopy height is a relevant proxy for aboveground biomass, carbon stock, and biodiversity. Wall-to-wall information of canopy height with high spatial resolution and accuracy is not yet available on large scales. For the globally consistent TanDEM-X data, simplifications are necessary to estimate canopy height with semi-empirical models based on polarimetric synthetic aperture radar interferometry (PolInSAR).
We trained the semi-empirical models with sampled GEDI data, because the assumptions behind the application of such simplifications are not always valid for TanDEM-X. General linear as well as sinc models and empirical parameterizations of these models were applied to estimate the canopy height in tropical landscapes of Sumatra, Indonesia. Airborne laser scanning (ALS) data were consistently used as an independent reference. The general simplified models were compared with the trained empirical versions to assess the potential improvement of the empirical parameterization of the models. The residuals of the different canopy height models were further evaluated in relation to land use and structural information of the vegetation.
Our results indicated that the empirical parameters substantially improved the estimation from a root-mean-square-error (RMSE) of 10.3 m (55.8%) to 8.8 m (47.7%), when using the linear model. In contrast, the improvement of the sinc model with empirical parameters was not substantial compared to the general sinc model (7.4 m [40.4%] vs. 6.9 m [37.5%]). A consistent improvement was observed in the linear model, whereas the improvement of the sinc model was dependent on the land-use type. Structural attributes like the canopy height itself and vegetation cover had a significant effect on the accuracies, with higher and denser vegetation generally resulting in higher residuals.
We demonstrate the potential of the combined exploitation of the TanDEM-X and GEDI missions for a wall-to-wall canopy height estimation in a tropical region. This study provides relevant findings for a consistent mapping of vegetation canopy height in tropical landscapes and on large scales with spaceborne laser and SAR data.
Original languageEnglish
Pages (from-to)1639-1656
Number of pages18
JournalMethods in ecology and evolution
Volume14
Issue number7
Early online date11 Jul 2022
DOIs
Publication statusPublished - Jul 2023

Keywords

  • GEDI
  • TanDEM-X
  • Coherence
  • Semi-empirical models
  • Tropical landscape
  • Vegetation canopy height

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