Abstract
Model-based forest height inversion from Pol-InSAR data relies on the realistic parameterization of the underlying (vertical) radar reflectivity function. In the context of interferometric TanDEM-X measurements – especially in the global single pol DEM mode – this is not possible due to the limited dimensionality of the observation space. In order to overcome this, the use of lidar waveforms to directly approximate the TanDEM-X reflectivity is proposed. This allows the forest height estimation from a single, single polarimetric, bistatic TanDEM-X acquisition. In order to extend the proposed lidar-supported inversion schema to areas only partially covered or sampled by (waveform) lidar measurements, the use of a “mean” (vertical) reflectivity profile is further proposed. This “mean” reflectivity profile is defined by means of the eigenfunctions of the available set of lidar waveforms. Both approaches are demonstrated and validated using TanDEM-X and airborne waveform lidar data acquired in the framework of the AfriSAR 2016 campaign over the Lope National Park, in Gabon.
Highlights
F OREST height is one of the most important forest parameters in forestry along with basal area and tree species or species composition
This work was performed in the frame of a joint research project between DLR and NASA’s Carbon Monitoring System (CMS) program in support of NASA Grant #80NSSC20K0023 to the University of Maryland. (Corresponding author: Matteo Pardini.)
Full waveform lidars as NASA’s airborne Land, Vegetation, and Ice Sensor (LVIS) [41] transmit short laser pulses to illuminate an area on the ground and receive the reflected distribution of energy, known as the waveform, as a function of time
Summary
F OREST height is one of the most important forest parameters in forestry along with basal area and tree species or species composition. Relying on the inherent sensitivity of the interferometric coherence to the vertical structure of volume scatterers combined with the potential of SAR polarimetry to characterize individual scattering processes, PolInSAR techniques have been established for accurate forest height estimation on large scales in the context of air- and spaceborne implementations [12]–[15]. When it comes to spaceborne repeat-pass implementations, the inherent presence of temporal decorrelation degrades the sensitivity of PolInSAR measurements to vertical scattering structure and limits the performance of PolInSAR inversion techniques [16]–[18].
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