Fix: unwrap response list phase before interpolation (#3585) - #3803
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Fix: unwrap response list phase before interpolation (#3585)#3803ThomasLecocq wants to merge 2 commits into
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A ResponseListResponseStage (frequency/amplitude/phase triplets) interpolated its phase with a cubic spline directly on the wrapped values. Across +/-180 degree phase wraps the spline overshoots wildly (Gibbs-like oscillation), producing spurious spikes in the response phase (and amplitude notches after evalresp) - clearly visible on real legacy FAP responses such as a Willmore Mk3 from a SEISAN file. Unwrap the phase before the spline and wrap the result back to (-180, 180]. The interpolant now follows the physical continuous phase and stays exact at the tabulated nodes. Amplitude interpolation is unchanged. Impact is minimal: only ResponseListResponseStage is affected (a rare stage type), and np.unwrap is a no-op unless adjacent phase samples jump by more than 180 degrees. FAP responses without wraps are bit-identical (verified on the bundled IM_IL31 response, whose existing full-evalresp test passes unchanged); only responses with genuine +/-180 wraps change, and only in the between-node regions that were previously wrong. Amplitude never changes. Regression test added (fails on master, passes here).
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September 1, 2026 14:27
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@krisvanneste here |
ThomasLecocq
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Sep 3, 2026
| - obspy.core: | ||
| * inventory: fix a bug that Latitude, Longitude and Distance did not accept | ||
| 'measurement_units' when being initialized (see #3623) | ||
| * inventory: unwrap the phase of a response list (FAP) stage before |
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gnee, have to put the changes in master
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A ResponseListResponseStage (frequency/amplitude/phase triplets) interpolated its phase with a cubic spline directly on the wrapped values. Across +/-180 degree phase wraps the spline overshoots wildly (Gibbs-like oscillation), producing spurious spikes in the response phase (and amplitude notches after evalresp) - clearly visible on real legacy FAP responses such as a Willmore Mk3 from a SEISAN file.
Unwrap the phase before the spline and wrap the result back to (-180, 180]. The interpolant now follows the physical continuous phase and stays exact at the tabulated nodes. Amplitude interpolation is unchanged.
Impact is minimal: only ResponseListResponseStage is affected (a rare stage type), and np.unwrap is a no-op unless adjacent phase samples jump by more than 180 degrees. FAP responses without wraps are bit-identical (verified on the bundled IM_IL31 response, whose existing full-evalresp test passes unchanged); only responses with genuine +/-180 wraps change, and only in the between-node regions that were previously wrong. Amplitude never changes.
Regression test added (fails on master, passes here).
Fixes #3585
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masterfor new features,maintenance_?.?.xfor bug fixesCHANGELOG.txt(only obsolete if fixing a bug introduced after the last release)ready for reviewlabel when you the PR is ready to be reviewed