Tropical-Forest Profiles and Biomass from TanDEM-X, Single-Baseline Interferometric SAR: InSAR Performance at Higher Frequencies and Bandwidths

Robert Neil Treuhaft, JPL, California Institute of Technology, robert.treuhaft@jpl.nasa.gov (Presenter)
Fabio G. Goncalves, Agrosatélite Geotecnologia Aplicada, fafabio@agrosatelite.com
Michael Keller, USDA Forest Service, mkeller.co2@gmail.com
João Roberto Santos, INPE, jroberto@ltid.inpe.br
Maxim Neumann, JPL, maxim.neumann@jpl.nasa.gov
Michael Palace, ESRC-University of New Hampshire, michael.palace@unh.edu

The principal method for remotely sensing forest biomass, particularly high-biomass tropical forests, is to measure vertical structural properties of the forest and relate them to biomass. Interferometric SAR (InSAR) and lidar are the two principal technologies applied to this task, with InSAR being coverage-rich and profile-info poor, and lidar being coverage poor and profile-info rich. InSAR is profile-info poor because, in the traditional, look-averaged analysis, it measures the vertical Fourier transform of the radar power at one vertical frequency specified by the baseline. Lidar produces a full profile, including all Fourier frequencies. In TanDEM-X data over tropical forests at the Tapajos National Forest, Brazil, we show the results of potentially improving InSAR’s Fourier coverage. This is done by estimating many Fourier frequencies with a single baseline, based on assumptions detailed in the poster. We show a similarity between the distribution of InSAR look-phase-heights (LPH) and lidar and field profiles over 0.25-ha areas. LPH is the height corresponding to a lateral radar sample of 1.5 x 2.5 meters, obtained before traditional look-averaging. Contrary to expectation, X-band penetration appears to be of the order of that of lidar. Using Fourier transforms of the histogram of LPH over 0.25 ha areas, biomass estimation improved by about 17% over using InSAR coherence and mean forest height, making it competitive with some lidar results. The RMS of biomasses estimated about field biomass was 48 Mg/ha, with biomasses as high as 430 Mg/ha, and an average of 174 Mg/ha. Perhaps LPH distributions bear a similarity to lidar and field profiles because shorter wavelengths (~3 cm) can penetrate holes in the canopy to scatter off a sample of the vegetation with each look. The holes effectively sample the vertical profile. This “hole mechanism” favors higher frequencies, which are able to penetrate smaller holes, and in this poster we explore the potential of high-frequency, high-bandwidth InSAR systems to complement lower frequency measurements.

Presentation: 2015_Poster_Treuhaft_246_135.pdf (4110k)

Presentation Type:  Poster

Session:  General Contributions   (Tue 4:35 PM)

Associated Project(s): 

• Treuhaft, Robert: Tropical Moist Forest Structure and Biomass Estimation from Bistatic InSAR at X-band (TanDEM-X), Small- and Large-Spot Lidar, and Field Measurements ...details

Poster Location ID: 246