## snap_graph.CoherenceConfig


Configuration for the coherence pipeline.


Usage

``` python
snap_graph.CoherenceConfig()
```


Inherits every parameter of [GeocodingConfig](snap_graph.GeocodingConfig.md#s1bursts.snap_graph.GeocodingConfig).

No `Multilook` step is applied, unlike [BackscatterConfig](snap_graph.BackscatterConfig.md#s1bursts.snap_graph.BackscatterConfig). It would save no runtime, since it can only sit after the coregistration and phase-removal stages that dominate this graph, and placing it after the `Coherence` operator averages coherence magnitudes and so cannot reduce the small-window estimator bias. Use `window` to set the looks.


## Parameters


`window`  
Coherence estimation window `(n_rg, n_az)` in single-look samples. This is the only control over the number of looks entering the estimator. SNAP's `squarePixel` option, which derives the azimuth window from the range window and the scene geometry, is pinned off, so the window given is the window applied.

`subtract_flat_earth_phase`  
Remove the flat-earth phase before estimating coherence.

`subtract_topographic_phase`  
Remove the topographic phase using `dem`.

`correct_coherence_bias`  
Remove the positive bias a finite estimation window leaves in the coherence magnitude. Requires SNAP 14; building the graph for an older or undetermined version raises [ConfigurationError](errors.ConfigurationError.md#s1bursts.errors.ConfigurationError). Off by default, unlike SNAP's own default, so that the estimator stays the one the window describes and stays comparable across SNAP versions.

`remove_local_phase_ramp`  
Let SNAP estimate and remove a local phase ramp within each estimation window before averaging, which recovers coherence lost to residual fringes. Requires SNAP 14, as above.


## Attributes

| Name | Description |
|----|----|
| [output_bands](#output_bands) | Names assigned to the output GeoTIFF bands by the SNAP client. |

------------------------------------------------------------------------


#### output_bands


Names assigned to the output GeoTIFF bands by the SNAP client.


`output_bands: list[str]`


## Methods

| Name | Description |
|----|----|
| [to_xml()](#to_xml) | Build the coherence graph XML for this config. |

------------------------------------------------------------------------


#### to_xml()


Build the coherence graph XML for this config.


Usage

``` python
to_xml(*, snap_version=None)
```


##### Raises


`ConfigurationError`  
If `correct_coherence_bias` or `remove_local_phase_ramp` is enabled but `snap_version` is older than 14 or unknown.