Comparison between TanDEM-X- and ALS-based estimation of aboveground biomass and tree height in boreal forests

ABSTRACT

Interferometric Synthetic Aperture Radar (InSAR) data from TerraSAR-X add-on for Digital Elevation Measurement (TanDEM-X) were used to estimate aboveground biomass (AGB) and tree height with linear regression models. These were compared to models based on airborne laser scanning (ALS) data at two Swedish boreal forest test sites, Krycklan (64°N19°E) and Remningstorp (58°N13°E). The predictions were validated using field data at the stand-level (0.5–26.1 ha) and at the plot-level (10 m radius). Additionally, the ALS metrics percentile 99 (p99) and vegetation ratio, commonly used to estimate AGB and tree height, were estimated in order to investigate the feasibility of replacing ALS data with TanDEM-X InSAR data. Both AGB and tree height could be estimated with about the same accuracy at the stand-level from both TanDEM-X- and ALS-based data. The AGB was estimated with 17.2% and 14.6% root mean square error (RMSE) and the tree height with 7.6% and 4.1% RMSE from TanDEM-X data at the stand-level at the two test sites Krycklan and Remningstorp. The Pearson correlation coefficients between the TanDEM-X height and the ALS height p99 were r = .98 and r = .95 at the two test sites. The TanDEM-X height contains information related to both tree height and forest density, which was validated from several estimation models.

KEYWORDS:

• TanDEM-X
• InSAR
• forest
• biomass
• height
• ALS
• SAR

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCiD

Henrik J. Persson http://orcid.org/0000-0002-3403-057X

Additional information

Funding

This study was financed by the Swedish National Space Board through the project “Retrieval of forest biomass and biomass change with spaceborne SAR”, contract No. 147/14; by the Hildur & Sven Wingquist’s Foundation for Forest Research; and by the European Community’s Seventh Framework Programme [FP7/2007–2013] under grant agreement no. [606971], the Advanced_SAR project. The TanDEM-X images were acquired through the German Aerospace Center (DLR) “3D forest parameter retrieval from TANDEM-X interferometry” project [XTI_VEGE0376].