insar-management-system-v2/docs/ISCE2_LT1_ENHANCEMENT_ALIGNMENT_20260427.md

ISCE2 LT-1 Enhancement Alignment 2026-04-27

Purpose

This note records why the managed ISCE2 lt1_stripmap production profile now enables the built-in stripmap enhancement steps by default, and how that choice relates to the existing SARscape custom6 production chain.

Background

The SARscape custom6 chain already goes beyond a bare minimum D-InSAR run. Its production semantics include:

1. Interferogram generation
2. Filtering and coherence
3. Orbital trend / residual phase frequency removal
4. Phase unwrapping
5. GCP-based refinement and reflattening
6. Phase to displacement and geocoding

This means the current LT-1 production baseline in the system is not a scientifically "raw" interferometric export. It is an operationally enhanced delivery chain.

ISCE2 Mapping

ISCE2 stripmap does not expose the exact same SARscape modules, but it does provide native enhancement steps that address the same operational risk class: residual misregistration and geometry-driven long-wavelength artifacts.

The relevant built-in ISCE2 controls are:

• doDenseOffsets
• doRubbersheetingRange
• doRubbersheetingAzimuth
• do split spectrum
• do dispersive
• rubberSheetSNRThreshold
• rubberSheetFilterSize

When enabled, the stripmap workflow:

• estimates dense offsets from cross-correlation
• filters / masks those offsets
• updates the geometry offset fields
• performs a fine resampling pass using the corrected offsets
• unwraps low/high-band interferograms and estimates a dispersive ionosphere term
• geocodes the ionosphere-corrected nondispersive phase for delivery

This is not identical to SARscape's RemoveResidualPhaseFrequency plus RefinementAndReflattening, but it is the closest native ISCE2 enhancement path inside the standard stripmap application.

Production Decision

The managed ISCE2 lt1_stripmap profile now treats these steps as part of the default LT-1 production workflow:

• split-spectrum ionosphere correction: enabled
• dense offsets: enabled
• range rubbersheeting: enabled
• azimuth rubbersheeting: enabled

Default numeric parameters:

• rubberSheetSNRThreshold = 5.0
• rubberSheetFilterSize = 9
• denseWindowWidth = 64
• denseWindowHeight = 64
• denseSearchWidth = 20
• denseSearchHeight = 20
• denseSkipWidth = 32
• denseSkipHeight = 32

These defaults are stored as profile semantics in code, not as loose .env feature toggles.

Runtime Dependency

The stripmap ionosphere implementation imports cv2 and scipy.

Deployment check:

/home/administrator/miniconda3/envs/insar_wsl_v1/bin/python -c "import cv2, scipy; print('ionosphere_ok')"

Repair command for an existing runtime:

conda install -n insar_wsl_v1 -c conda-forge opencv scipy

The range rubbersheeting implementation in ISCE2 imports astropy.convolution from runRubbersheetRange.py. The shared WSL conda runtime therefore must include astropy.

Deployment check:

/home/administrator/miniconda3/envs/insar_wsl_v1/bin/python -c "from astropy.convolution import convolve; print('astropy_ok')"

Repair command for an existing runtime:

conda install -n insar_wsl_v1 -c conda-forge astropy

Boundary

This change does not mean that every long-wavelength ramp problem is solved.

It only means the default managed ISCE2 LT-1 profile now includes the native registration-enhancement path that was previously omitted.

If a run still shows a strong residual scene-wide ramp after rubbersheeting, that should be treated as a separate quality / post-processing issue and should be diagnosed explicitly rather than silently hidden inside export logic.

Operational Implication

When comparing current SARscape and ISCE2 LT-1 products:

• SARscape custom6 remains the more explicitly refined chain
• ISCE2 lt1_stripmap is no longer a bare stripmap baseline
• both engines now include standard enhancement intent in default production

This makes cross-engine behavior more defensible for LT-1 operational delivery.

Operator Controls

As of 2026-04-29, the production UI no longer hides these choices behind code defaults only.

The ISCE2 production panel now exposes the managed LT-1 profile parameters in three groups:

• Execution
• Delivery
• Enhancement

The user-visible controls now cover:

• split-spectrum ionosphere correction on/off
• dense offsets on/off
• range rubbersheeting on/off
• azimuth rubbersheeting on/off
• reference normalization mode (coh_median or none)
• deramp mode (plane or none)

This keeps the default managed behavior unchanged, while allowing operators to fall back toward a more conservative stripmap delivery path when a specific scene looks worse after enhancement.