Wind direction estimation from SAR images of the ocean using wavelet analysis
Bibliographic record
Abstract
We present a method for the automatic estimation of wind directions from synthetic aperture radar (SAR) images of the ocean. The method is based on a wavelet analysis and assumes that the wind direction aligns with boundary-layer atmospheric roll vortices, which often appear as streaks at kilometre scales in SAR images of the ocean, and measures the orientation of the streaks. Unlike estimation methods that use the discrete Fourier transform (DFT), the streaks in SAR images are described quantitatively as a natural output of this method. Furthermore, more optimal wind directions are obtained by comparing the directional orientation of the streaks at different spatial scales. Sub-scenes in which the streaks are too weak to determine wind direction do not return a direction, as governed by a user-selected threshold. Wind directions for these sub-scenes are based on those in neighbouring sub-scenes by using an adaptive smoothing technique. Quality control involves tuning the threshold level. We apply the method to two examples of RADARSAT-1 SAR images. The results are compared with those of a DFT-based wind direction analysis, and it is shown that a robust wind direction field is obtained. Mesoscale wind structures can be described by using a finer computing grid. The estimated wind directions still include a 180° direction ambiguity.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".