Mono- and bistatic UHF-band SAR measurements of a hemi-boreal forest

In this paper, the potential of mono- and bistatic HH-polarized UHF-band SAR imagery for mapping of a hemi-boreal forest is studied. SAR data have been acquired with the two airborne SAR sensors LORA and SETHI during a joint FOI-ONERA campaign conducted in 2010. Three acquisition modes are compared: monostatic, quasi-monostatic (difference in elevation angle around 0°) and bistatic (difference in elevation angle around 6°). Images acquired at two perpendicular flight headings are used, i.e. 178° and 268°, to evaluate the influence of topography, which often has an aggravating effect on forest variable estimation. It is observed that for the quasi-monostatic and bistatic acquisitions, the influence of ground topography is lower compared to the monostatic acquisition. A linear regression model is used to explain the dependence of the backscattering coefficient on the logarithm of biomass, and it is observed that the estimated intercept and slope are similar for the two headings only in the case of quasi-monostatic and bistatic acquisitions, of which the latter features the lowest error and the highest coefficient of determination (0.73 and 0.70, respectively, for headings 178° and 268°).