New CWL Application Package - Visualisation

[james-hinton]

A new application package that generates an NDVI PNG from a Sentinel-2 STAC item. Similar to https://github.com/EOEPCA/deployment-guide/blob/main/scripts/processing/oapip/examples/app-water-bodies-cloud-native.1.5.0.cwl but simpler.

Inputs

• stac_item (string) - URL to a Sentinel-2 STAC Item from Earth Search
• aoi (string, optional) - Bounding box as minx,miny,maxx,maxy in EPSG:4326

Output

• PNG showing NDVI with a colour ramp
• STAC Catalog for the output

Example

{
  "inputs": {
    "stac_item": "https://earth-search.aws.element84.com/v1/collections/sentinel-2-l2a/items/S2A_34SEG_20240721_0_L2A",
    "aoi": "21.0,37.0,21.5,37.5"
  }
}

Use the water bodies CWL as a starting point, the existing tools can be reused:

• crop - ghcr.io/terradue/ogc-eo-application-package-hands-on/crop:1.5.0
• norm_diff - ghcr.io/terradue/ogc-eo-application-package-hands-on/norm_diff:1.5.0 (this is generic, works for NDVI with nir and red bands)
• stac - ghcr.io/terradue/ogc-eo-application-package-hands-on/stac:1.5.0

NDVI calculation: grab the nir (B08) and red (B04) assets from the STAC item, then calculate (nir - red) / (nir + red).

What needs creating

1. visualise tool - Python script that takes an NDVI GeoTIFF, applies a colour ramp, outputs PNG
2. Dockerfile for the visualise tool
3. CWL workflow tying it all together (based on water-bodies structure but without the Otsu step, adding visualise instead)

Reference

• https://github.com/EOEPCA/deployment-guide/blob/main/scripts/processing/oapip/examples/app-water-bodies-cloud-native.1.5.0.cwl
• https://github.com/EOEPCA/deployment-guide/blob/main/scripts/processing/oapip/examples/convert-url-app.cwl
• https://github.com/eoap/application-package-patterns/tree/main
• Example STAC item: https://earth-search.aws.element84.com/v1/collections/sentinel-2-l2a/items/S2A_34SEG_20240721_0_L2A

Done when

• CWL workflow file that orchestrates the steps
• Python script for the visualise tool
• Dockerfile for the visualise tool