Delineation of delta ecozones using interferometric SAR phase coherence: Mackenzie River Delta, N.W.T., Canada

Abstract

Interferometric processing of six C-band synthetic aperture radar (SAR) image pairs for the Mackenzie River Delta shows that phase coherence is more effective than radar backscatter for differentiating willow–alder, spruce, ice, and open water. Similar radar backscattering from vegetation and wind-roughened water surfaces can make such distinctions difficult in SAR backscatter images. In contrast, coherence is preserved over surfaces with rigid scattering elements, such as leafless woody alder, but is lost over temporally unstable surfaces such as open water. We find that willow–alder display highest coherence followed by spruce, frozen lakes and channels, and open water, respectively. This general hierarchy is preserved even when overall image coherence is decreased by increasing temporal and spatial baselines. Evaluation of spatial, thermal noise and temporal components of total observed coherence indicates that temporal decorrelation is a primary control. Short temporal baselines, such as those obtained during the European Remote Sensing Satellite (ERS) 1-day tandem missions, are therefore optimal for obtaining maximum differentiation of surface classes.