IEEE Geoscience and Remote Sensing Magazine - June 2020 - 30

Forest SAR Tomography
Principles and applications
HOSSEIN AGHABABAEI,
GIAMPAOLO FERRAIOLI,
LAURENT FERRO-FAMIL,
YUE HUANG, MAURO MARIOTTI
D'ALESSANDRO, VITO PASCAZIO,
GILDA SCHIRINZI, AND STEFANO TEBALDINI

S

ynthetic-aperture radar (SAR) systems are widely
used for monitoring vegetation and forested environments. Those that offer large-scale coverage, short revisiting times, and an under-foliage wave-penetration capability have been broadly employed to extract information
about the forest structure. Similarly, 3D forest structures
that serve as important indicators of productivity and
biomass levels can be efficiently estimated using the SAR
tomography (TomoSAR) processing technique through
multibaseline (MB) image acquisition. This article provides an overview of the main developments in forest
TomoSAR during the past two decades.
MONITORING FORESTED AREAS
Characterizing and monitoring forested areas are highly important activities for tracking climate change and
quantifying the global carbon cycle in the form of aboveground-biomass (AGB) mapping. Forest environments
play profound roles in resource utilization, ecology, and
biodiversity applications [1], a fact that highlights the significance of monitoring them. Forest characterization is
mainly associated with the identification of its vertical
structure, which typically represents the arrangement of
the trees, trunks, and crown. The forest structure constitutes a significant indicator of productivity and biomass level and thus is recognized by the scientific community as a major element in forest monitoring [2]-[4].
Structure variation can reveal the dynamics of the forest, and the temporal evolution of the AGB distribution
can be inferred from monitoring the forest structure at
a global scale [5].
In situ forest monitoring provides the most accurate data
parameters but involves expensive and time-consuming
field work. Remote sensing techniques have the advantage
of consistent, large-scale coverage and short revisiting times
that can ease the difficulties that are encountered with
traditional approaches. Remote sensing techniques that
Digital Object Identifier 10.1109/MGRS.2019.2963093
Date of current version: 12 February 2020

30

0274-6638/20©2020IEEE

guarantee under-foliage penetration capabilities and enable
3D measurements (not only the horizontal variability but
the vertical parameter) are best suited to forest monitoring.
High-resolution waveform lidar and TomoSAR [6] are
the two most popular approaches to 3D forest monitoring,
and their different sensing technologies result in advantages and drawbacks for each. Among them, the remarkable
advantages of SAR, which is almost independent of weather conditions due to the ability of microwaves to penetrate
semitransparent media and cover a larger study area, have
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JUNE 2020
IEEE Geoscience and Remote Sensing Magazine - June 2020

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