Evaluation of JERS-1, ERS-1 and Almaz SAR backscatter for rubber and oil palm stands in West Malaysia

While many reports have been published on radar backscatter characteristics of coniferous and deciduous forests, little work appears to have been done on investigating the backscatter properties of palm trees. In this study, Japanese JERS-1 L(HH) band, European ERS-1 C-VV band and Russian Almaz-1B S-HH band SAR data have been acquired over parts of Kedah and Penang states in West Malaysia in order to investigate the radar backscatter properties for oil palms and rubber trees for each of these sensors. Results show that the radar backscatter for the deciduous rubber trees, for both JERS-1 and ERS-1, appear to behave in accordance with what has been reported earlier for coniferous and deciduous trees, that is, scattering on trunks, branches and twigs at L-band and scattering in the canopy at C-band. The JERS-1 backscatter shows limited correlation with the rubber growth while no relation is found in the ERS-1 data. Oil palms with their characteristic structures affect the radar signal differently compared to the situation for rubber trees. Scattering in the large crown is the dominating backscatter mechanism in both the JERS-1 and ERS-1 data. Leaf area index is correlated closest to the backscatter intensity at both bands. Results from the investigation of the Almaz S-band data are rather discouraging, contradicting earlier more positive reports on the usefulness of the sensor. In this study, the forest types and their intermediate growing stages were found to be virtually indistinguishable, including the clear felled areas. These results should however not be attributed to S-band or Almaz data in general, but rather to this particular data set. It is obvious that the quality of Almaz data varies significantly.