MONITORING OF TROPICAL TREE CROPS BY JERS-1 AND ERS-1 SAR DATA

  Ake Rosenqvist
  Earth Observation Center
  National Space Development Agency of Japan
  1401 Numanoue, Ohashi, Hatoyama-machi
  Hiki-gun, Saitama 350-03, Japan
  E-mail: ake@heoc.eoc.nasda.go.jp


  While many reports have been published on radar backscatter
  characteristics of coniferous and deciduous tree types, little work
  appears to have been done on investigating the backscatter properties of
  palm trees. In this study, JERS-1 LHH band and ERS-1 CVV band SAR data
  have been acquired over parts of Kedah and Penang states in West Malaysia
  in order to investigate the radar backscatter properties of two common
  tree crops in the tropical region with significantly different
  structures. RTraditionalS deciduous tree s are here represented by rubber
  trees, while palm trees are represented by oil palms.

  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 up to a level where the signal saturates. This
  corresponds to an intermediate growth stage where the trees have reached
  a height of about half that of fully grown rubber trees (~20 m). The
  bio-physical parameter that correlates best with the L-band response is
  the average stand height. Not surprisingly, ERS-1 C-band data display
  poor correlation with the growth of rubber trees and depending on the
  conditions of the soil and under cover vegetation, even cleared areas are
  often difficult to distinguish from mature plantations.

  Oil palms, with their characteristic straight, rough trunks and large
  umbrella shaped crowns, on the other hand affect the radar signal
  differently at both L- and C-band. At L-band, scattering in large crown
  is the dominating backscatter mechanism, with little or no penetration
  through the thick canopy. This results in poor correlation with trunk
  height or above ground biomass. Crown related factors such as Leaf Area
  Index and frond length correspond best to the radar response, with the
  developed. In contrast to the poor correlation with rubber growth, C-band
  backscatter displays strong correlation with the growth of the palm
  trees. The C-band response is almost identical to that for L-band, i.e.
  scattering on the large crown and saturation for a closed canopy.

  Distinction between the two tree species (for stands above the saturation
  level) is feasible at both frequencies, although C-band data displays
  slightly better results due to a larger difference in the saturation
  levels between the two species.

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry