Abstract
CRL/NASDA airborne synthetic aperture radar (Polarimetric Interferometric SAR, PI-SAR) has functions to observe in 2 frequencies (X and L-band), high spatial resolution and full polarimetry. This paper aims to analyze the characteristics of PI-SAR data applied for forest observation.
We tried some filtering methods for speckle noise reduction, and recognized that the Frost Filter (3x3) is the most adequate. We compared distinctive abilities between PI-SAR false color composite images (Red, Green, Blue : HH, HV, VV respectively) and TM/CASI/aerial photograph images. It was verified that L-band image showed the feature of tree species as the tone of color, and X-band showed surface texture of forest crown. An inspection of relationship between forest parameters and PI-SAR backscatter coefficient was conducted.
In order to avoid the incident angle effect,
1. flight path was set parallel along with straight forestry road about 8 km long.
2. research plots for forest measurement were placed near that forestry road.
Distinctive features were expected in the relationship between PI-SAR observation parameters and forest parameters. We measured forest parameters such as leaf area index (LAI), basal area, diameter at breast height (DBH) and top height during a few days just after observation of PI-SAR, and analyzed the relationship in evergreen artificial forest. We also considered about appropriate sampling extent on PI-SAR data for the representative value of the dB for comparison. As the result, we found that L-HV, VH, VV data have significant correlation with forest parameters.
L-HH suggested the possibility to distinguish the three categories of tree species (1. evergreen coniferous trees 2. Larix 3. broad leaf trees). We estimated trunk biomass from basal area and standard tree of the stand. And considering about saturation of L-band for forest biomass, we realized that measured plots have smaller volume than saturation revel at L-VV, but bigger at L-HH. The relationship of L-VV and trunk biomass of plots was discribed as σ∝ ∝(trunk biomass)0.28.
