Canopy height estimation with TanDEM-X in temperate and boreal forests

Schlund, Michael; Magdon, Paul; Eaton, Brian; Aumann, Craig; Erasmi, Stefan

doi:10.1016/j.jag.2019.101904

Cited by 20 publications

(38 citation statements)

References 45 publications

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“…VOL). The accuracy in terms of the coefficient of determination and the RMSE p is comparable to other studies based on single-pol X-band InSAR data that used ancillary data for the ground phase [21,58] or evaluated physical models for the prediction of forest structural parameters [20].…”

Section: Discussionsupporting

confidence: 70%

“…The effect of wavelength on retrieving forest height from the random volume over ground (RVoG), a two-layer and vertical structure model, and its inversion was recently demonstrated by [15] who compared X-, C-, and L-band and found that the RMSE of forest height inversion increased with increasing frequency. Nevertheless, single-polarized X-band InSAR data are used in scattering models under simplified assumptions or when ancillary data are available to replace missing scattering information of the ground layer [16][17][18][19][20]. Compared to these simplified scattering models, the second approach is dependent on the availability of ancillary data, e.g., a digital terrain model to derive information about the ground height.…”

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confidence: 99%

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Sensitivity of Bistatic TanDEM-X Data to Stand Structural Parameters in Temperate Forests

et al. 2019

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Synthetic aperture radar (SAR) satellite data provide a valuable means for the large-scale and long-term monitoring of structural components of forest stands. The potential of TanDEM-X interferometric SAR (InSAR) for the assessment of forest structural properties has been widely verified. However, present studies are mostly restricted to homogeneous forests and do not account for stratification in assessing model performance. A systematic sensitivity analysis of the TanDEM-X SAR signal to forest structural parameters was carried out with emphasis on different strata of forest stands (location of the study site, forest type, and development stage). Forest structure was parameterized by forest height metrics and stem volume. Results show that X-band volume coherence is highly sensitive to the forest canopy. Volume scattering within the canopy is dependent on the vertical heterogeneity of the forest stand. In general, TanDEM-X coherence is more sensitive to forest vertical structure compared to backscatter. The relations between TanDEM-X volume coherence and forest structural properties were significant at the level of a single test site as well as across sites in temperate forests in Germany. Forest type does not affect the overall relationship between the SAR signal and the forests' vertical structure. The prediction of forest structural parameters based on the outcome of the sensitivity analysis yielded model accuracies between 15% (relative root mean square error) for Lorey's height and 32% for stem volume. The global database of single-polarized bistatic TanDEM-X data provides an important source for mapping structural parameters in temperate forests at large scale, irrespective of forest type. and ranging (LiDAR), and synthetic aperture radar (SAR) data. A comprehensive summary of studies that aim at quantifying forest biomass from satellite sensors was compiled by [3]. AGB estimates from optical remote sensing data mostly rely on vegetation indices that parameterize the photosynthetic activity of vegetation. They imply a relationship between the foliage and the total AGB of a vegetation stand, which is further used to estimate AGB. Since the major part of AGB in forests is composed of non-photosynthetic (woody) components, such approaches imply high uncertainties. The major challenge in AGB mapping from optical data is the saturation of the signal after canopy closure which especially hampers the estimation of high-level AGB [4]. However, recent studies confirmed the general ability of optical systems like Landsat to map AGB at biomass levels around 70 Mg/ha [5].The saturation problem can be overcome by sensors, which are able to penetrate through the canopy and interact with the forest constituents. For instance, LiDAR and interferometric SAR (InSAR) systems generally provide the necessary technique because they are able to penetrate the canopy of a forest and deliver information about the vertical structure of a forest stand. LiDAR data produce high-accuracy canopy height models (CHM) but the main drawback ...

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Section: Discussionsupporting

confidence: 70%

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confidence: 99%

Sensitivity of Bistatic TanDEM-X Data to Stand Structural Parameters in Temperate Forests

et al. 2019

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“…In absence of temporal decorrelation, and thanks to the large baselines available (i.e., short HoA values), volume decorrelation, γ vol , is the dominating decorrelation source [45] and provides sensitivity to vegetation height and structure. Volume decorrelation has been exploited in applications of TanDEM-X for vegetation height retrieval, both in forests [3,34,46,47] and crops [35,48]. As the vegetation height increases, volume scattering effects result in a larger coherence loss, and other structural changes produce also variations in coherence.…”

Section: Time Seriesmentioning

confidence: 99%

Exploring TanDEM-X Interferometric Products for Crop-Type Mapping

et al. 2020

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The application of satellite single-pass interferometric data to crop-type mapping is demonstrated for the first time in this work. A set of nine TanDEM-X dual-pol pairs of images acquired during its science phase, from June to August 2015, is exploited for this purpose. An agricultural site located in Sevilla (Spain), composed of fields of 13 different crop species, is employed for validation. Sets of input features formed by polarimetric and interferometric observables are tested for crop classification, including single-pass coherence and repeat-pass coherence formed by consecutive images. The backscattering coefficient at HH and VV channels and the correlation between channels form the set of polarimetric features employed as a reference set upon which the added value of interferometric coherence is evaluated. The inclusion of single-pass coherence as feature improves by 2% the overall accuracy (OA) with respect to the reference case, reaching 92%. More importantly, in single-pol configurations OA increases by 10% for the HH channel and by 8% for the VV channel, reaching 87% and 88%, respectively. Repeat-pass coherence also improves the classification performance, but with final scores slightly worse than with single-pass coherence. However, it improves the individual performance of the backscattering coefficient by 6–7%. Furthermore, in products evaluated at field level the dual-pol repeat-pass coherence features provide the same score as single-pass coherence features (overall accuracy above 94%). Consequently, the contribution of interferometry, both single-pass and repeat-pass, to crop-type mapping is proved.

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“…InSAR images at C-band were used by [54] to estimate stem volume and attained a RMSE value of 27%. Schlund et al [55] modelled canopy height in boreal and temperate forests based on single-polarized TandDEM-X data. The authors used the RVoG model to estimate tree heights and validated their results with LiDAR data.…”

Section: Canopy Height Estimationmentioning

confidence: 99%

“…The authors used the RVoG model to estimate tree heights and validated their results with LiDAR data. The R 2 lied between 0.08-0.64 and the RMSE varied from 4.8 to 13.5 m [55]. Khati et al [53] analyzed Indian tropical canopy heights based on TS-X/TanDEM-X data and attained RMSEs from 2.71-3.17 m for different seasons using the RVoG inversion approach.…”

Section: Canopy Height Estimationmentioning

confidence: 99%

Canopy Height and Above-Ground Biomass Retrieval in Tropical Forests Using Multi-Pass X- and C-Band Pol-InSAR Data

et al. 2019

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Globally available high-resolution information about canopy height and AGB is important for carbon accounting. The present study showed that Pol-InSAR data from TS-X and RS-2 could be used together with field inventories and high-resolution data such as drone or LiDAR data to support the carbon accounting in the context of REDD+ (Reducing Emissions from Deforestation and Forest Degradation) projects.

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Canopy height estimation with TanDEM-X in temperate and boreal forests

Cited by 20 publications

References 45 publications

Sensitivity of Bistatic TanDEM-X Data to Stand Structural Parameters in Temperate Forests

Sensitivity of Bistatic TanDEM-X Data to Stand Structural Parameters in Temperate Forests

Exploring TanDEM-X Interferometric Products for Crop-Type Mapping

Canopy Height and Above-Ground Biomass Retrieval in Tropical Forests Using Multi-Pass X- and C-Band Pol-InSAR Data

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