Model-based forest height inversion from single- and multi-baseline polarimetric synthetic aperture radar interferometry (Pol-InSAR) data is today well-established. One of the critical performance points is the parameterization of the vertical reflectivity profile. In this article, the parameterization of the vertical reflectivity profile using a tomographic reconstruction is proposed. To mitigate the limitations in the tomographic reconstruction induced by the limited vertical resolution especially for the ground-scattering component, the ground and volume contributions are separated using the sum of Kronecker products (SKPs) decomposition. For the forest height inversion, the Pol-InSAR line inclination angle is proposed, which, unlike the absolute coherence and the phase center, is invariant to the presence of a residual Dirac-like ground-scattering contribution. The inversion performance is addressed and compared for both single- and multi-baseline cases, in the absence and presence of temporal decorrelation. In all cases, the ground elevation is estimated from the tomographically reconstructed vertical reflectivity profiles and its accuracy directly influences the achieved inversion performance. The proposed methodology establishes a link between interferometric and tomographic measurements and is therefore relevant for missions that allow the implementation of both techniques. ESA’s BIOMASS is one such mission, and as such is being used as a test case to discuss different implementation scenarios. The different inversion strategies are applied to P-band campaign data acquired in the frame of the AFRISAR 2016 experiment and validated against reference measurements.

The combination of TanDEM-X interferometric measurements with GEDI lidar full waveform measurements can provide continuous high-resolution forest height maps at global scale with sufficient accuracy without using external information about the underlyingtopography. In previous studies, the GEDI lidar full waveforms have been used to provide an approximation of the TanDEM-X X-band (radar) vertical reflectivity function in the height inversion of an entire TanDEM-X scene. This framework has been applied to the whole the whole Brazilian Amazon, and the obtained results are presented and analyzed in this paper. More than 12,000 TanDEM-X scenes and 250 millions GEDI lidar measurements have been processed.have.

Polarimetric SAR Interferometry (Pol-InSAR) is a SAR remote sensing discipline with unique and powerful applications related to the vertical structure of natural and man-made volume scatterers. The coherent combination of single- or multi -baseline interferograms acquired at different polarisations provides sensitivity to the vertical distribution of scattering processes and allows their characterisation by using the associated (volume) interferometric coherences.

The TerraSAR-X add on for Digital Elevation Measurement (TanDEM-X) mission provides Interferometric Synthetic Aperture Radar (InSAR) wall-to-wall data (not sparse) at high resolution and at global scale. In addition, the NASA Global Ecosystem Dynamics Investigation (GEDI) is a new spaceborne system that provides (from 51.6°N and 51.6°S) sparse measurements (not images) through LiDAR waveforms. Both systems are sensitivity to the canopy structure such as the forest height but with their own limitations. The TanDEM-X single polarization (HH) interferometric coherence magnitude at X-band provides a continuous mapping of the forest while GEDI provides accurate (but sparse) measurements of the forest. In this paper a methodology of how to combine both systems to estimated forest height is presented and applied to more than 900 TanDEM-X scenes over Gabon in Africa. The forest height results over an area of 1° by 1° are shown and compared respect to GEDI. Finally, a wall-to-wall forest map over the entire country of Gabon is presented as an example of large scale mapping towards a potential global (entire earth) forest height map.

The realistic parameterization of the underlying (vertical) radar reflectivity profile is critical for a model-based inversion of forest height from polarimetric interferometric (Pol-InSAR) data. Indeed, an appropriate parameterization not only affects the final estimation performance, but also enables the inversion from a reduced observation space in terms of number of baselines and / or polarizations. Here, we investigate the possibility of using a full tomographic profile to parameterize the inversion. The proposed methodology is demonstrated and validated using Pol-InSAR and tomographic data acquired in the framework of relevant airborne campaigns.

Polarimetric SAR Interferometry (Pol-InSAR) is a SAR remote sensing discipline with unique and powerful applications related to the vertical structure of natural and man-made volume scatterers. The coherent combination of single- or multi -baseline interferograms acquired at different polarisations provides sensitivity to the vertical distribution of scattering processes and allows their characterisation by using the associated (volume) interferometric coherences [1]–[5].

TanDEM-X experiments have shown that forest height can be estimated with single polarization X-band interferometric coherences. An external digital terrain model (DTM) not only allows to use both coherence magnitude and phase information, but also to overcome X-band penetration limitations. However, DTM information is not available for large areas. Using coherence magnitudes makes height inversion feasible, but it requires a model relating coherence to height. Here we report an experiment using the X-band local phase center variations. Results over a tropical forest site show that in those stands in which the low X-band penetration is not a limitation, the there is a good correlation between the obtained TanDEM-X heights and the heights from Lidar measurements.