Interactive Application
Explore the full analysis dashboard below. Navigate between tabs to view 3D echograms, 2D cross-sections, layer details, echo-free zone analysis, and forward models. The app may take a moment to load on first visit.
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Overview
ApRES is an FMCW radar system used to measure internal ice deformation with millimeter precision. Deployed on the Mercer Ice Stream in Antarctica, it yields a depth profile of internal layers that can be tracked over time.
This project focuses on the echo-free zone, the region near the bed where clear layers vanish. We apply phase-sensitive analysis and advanced denoising to extract persistent phase signals, revealing ice dynamics that are otherwise hidden.
Key Methods
Two complementary techniques form the core of the velocity analysis: one operating in the phase domain, the other using optimal path finding through the echogram.
Phase-Slope Velocity Estimation
Estimates vertical velocity directly from the phase field gradient. By fitting a slope to unwrapped phase windows, it produces continuous velocity profiles without needing discrete reflectors. This approach successfully uncovers coherent signals deep within the echo-free zone.
Viterbi Layer Tracking
Treats layer tracking as a hidden Markov model to find the globally optimal path through the echogram. This produces robust trajectories that bridge amplitude gaps, making it ideal for tracking layers that weaken near the echo-free zone boundary.
Key Finding · Coherent Signal in the Echo-Free Zone
The "echo-free zone" is not entirely echo-free. Coherent phase signals persist well below the deepest visible layers, producing velocity estimates that smoothly continue the profile. This provides new constraints on ice dynamics closer to the bed.
Ongoing Research · Nature of the EFZ Signal
We are investigating the physical origin of these signals. Three hypotheses are currently being explored using MCMC probabilistic fitting and CLEAN deconvolution:
- Specular layers: intact dielectric contrasts too weak for amplitude detection.
- Rayleigh scatterers: volumetric scattering from distributed inhomogeneities.
- Broken layers: previously continuous layers disrupted by ice dynamics.