[Sentinel-1 GRD] Accessing the Incidence Angle Map

[fabito]

I'm looking to extract the incidence angle map band from Sentinel-1 GRD products, in addition to the VV and VH bands that are already supported.

Specific Goal & Requirement:

• Inputs: Sentinel-1 GRD product and a 1-meter resolution DEM.
• Output: A 3-band Cloud-Optimized GeoTIFF (COG) with bands: VV, VH, and the incidence angle (preferably in radians).

Does eoreader currently support the generation of the local incidence angle map by incorporating an external DEM? If so, could anyone share an example of the configuration or method?

Thanks for any help or pointers!

[remi-braun]

Sadly I never saw this usecase and this is not implemented.
Is this doable with SNAP?

[fabito]

GEE exposes it: https://developers.google.com/earth-engine/datasets/catalog/COPERNICUS_S1_GRD#bands

I think the SNAP's Terrain-Correction operator can output incidence angle data through:

  <node id="Terrain-Correction">
    <operator>Terrain-Correction</operator>
    <parameters>
        <sourceBands/>
        <saveIncidenceAngleFromEllipsoid>true</saveIncidenceAngleFromEllipsoid>
        <saveLocalIncidenceAngle>true</saveLocalIncidenceAngle>
        <saveProjectedLocalIncidenceAngle>true</saveProjectedLocalIncidenceAngle>
    </parameters>
  </node>

From docs:

Incidence angle ellipsoid: Checkbox indicating that the tie point grid incidence angle will be saved as a band in the target product.
Local incidence angle: Checkbox indicating that local incidence angle will be saved as a band in the target product.
Projected (into the range plane) local incidence angle: Checkbox indicating that the projected local incidence angle will be saved as a band in the target product.

[remi-braun]

Ok, this can be done, however I have no usecase for this at all.
As I am a bit swamped, feel free to open an issue and create a PR to solve it 🙏

[remi-braun]

@simone-tilia I see your fork seems to answer this topic (at least partially).
Would you mind to submit a PR if you are confident in your code?

[remi-braun]

LIA should be accessible since 0.23.0 : https://eoreader.readthedocs.io/stable/sar.html#local-incidence-angles