F. G. Goncalves

Mapping recent deforestation in the Brazilian Amazon using simulated L-band MAPSAR images

Brazilian Amazon Forest biomes are presently under intensive land cover conversion from natural vegetation to agriculture. Timely detection of recent deforestation through orbital remote sensing is a critical requirement for an operational land cover monitoring system in order to provide information to the regulatory systems and decision makers. Optical images present drawbacks for operation in the moist tropics and synthetic aperture radar (SAR) data are a real alternative. The feasibility of using multipolarized L‐band images simulating the Multi‐Application Purpose SAR (MAPSAR) satellite was examined for the detection of recent deforestation in the Tapajós region. The discrimination of recent deforestation from other land cover classes was evaluated through a quantitative analysis based on Jeffreys–Matusitas (JM) distances derived from training samples using amplitude values and supported by field survey. The investigation confirmed the possibility of the discrimination of recently deforested classes from other classes based on the L‐band images as proposed in the MAPSAR.

Analysis of airborne SAR data (L-band) for discrimination land use/land cover types in the Brazilian Amazon region

The objective of this paper is to show the potential of multi-polarized mosaic-images from a MAPSAR (L-band) simulation campaign performed in the Amazon region (test site Tapajos) in order to discriminate land use/land cover classes. An Enhanced-Frost filter was used and the thematic discrimination was done by an algorithm for attribute extraction based on Bhattacharya distance. A comparison was made among the radiometric aspects of the SAR mosaic for 10 thematic classes obtained, converting these B-distances to JM distance values. This allowed to define which individual or multiple polarizations are more appropriate for the identification of thematic classes.

Biomass change in disturbed, secondary, and primary tropical forests from TanDEM-X

The time variation of phase height from interferometric SAR (InSAR) from TanDEM-X is shown for 3 years, in Tapajos National Forest, Brazil. Its RMS, for one secondary stand, about a model linear in time is 0.5 m. This RMS is compared to that for 30 stands at one epoch. The single-epoch RMS for a model linear in mean field height is 2.2 m. It is suggested that the improved performance of the temporal variation may be due to errors in finding the phase height of the ground, which is necessary for single-epoch estimation, but not needed for the “change” measurement. Pending further fieldwork, a tentative conversion of 20 Mg/ha/yr corresponding to 1 m/yr, is proposed. Abrupt discontinuities, as well as phase height rates as a function of stand age/aboveground biomass, are discussed.