Search

Properties of multi-temporal ERS-1/2 tandem coherence in boreal forests and retrieval accuracy of forest stem volume have been investigated mostly for small, managed forest areas. The clear seasonal trends and the high accuracy of the retrieval are therefore valid for specific types of forest and question is if these findings extend to large areas with different forest types in a similar manner. Using multi-temporal ERS-1/2 coherence data and extensive sets of inventory data at stand level at seven forest compartments in Central Siberia we confirm that the trend of coherence as a function of stem volume is mainly driven by the environmental conditions at acquisition. In addition, we have now found that the variability of the coherence for a given stem volume are due to spatial variations of the environmental conditions, strong topography (slope > 100), small stand size (< 3-4 ha) and low relative stocking (< 50%). Further deviations can be related to errors in the ground data. Stem volume retrieval behaves consistently under stable winter frozen conditions. For stands larger than 3 -4 ha and relative stocking of at least 50%, a relative RMSE of 20 -25% can be considered the effective retrieval error achievable in Siberian boreal forest. Combined with previous experience from managed test forests in Sweden and and Finland, C-band ERS-1/2 tandem coherence observations acquired under stable winter conditions with a snow cover and an at least moderate breeze can be considered so far the most suitable spaceborne remote sensing observable for the estimation of forest stem volume in homogeneous forest stands throughout the boreal zone.

A least-mean-square algorithm in the frequency domain, with amplitude normalisation. is proposed to remove narrowband radio frequency interference in low-frequency ultra-wideband synthetic aperture radar systems. The performance uf the algorithm was tested on experimental data acquired with the CARABAS system.

Retrieval of forest stem volume shows great promise using SAR in the lower

The problem of wave interactions in a dispersive medium with a density periodic in time and space due to a high power pump wave, is treated. Waves are shown to be caused by both scattering and boundary processes. Conditions for parametric traveling wave resonance are found. Generalized Fresnel formulas are given for parallel and perpendicular polarization. (Author), Available copy will not permit fully legible reproduction. Reproduction will be made if requested by users of DDC. Copy is available for public sale.