Why, How, and When to Use the New Target Sensor in the Harmonization Tool

Why, How, and When to Use the New Target Sensor in the Harmonization Tool

Planet operates three generations of Doves (Dove Classics, Dove-R, SuperDove) that have different spectral responses. In order to use images from all Doves interchangeably they need to be normalized to a single target so all images' spectral responses align closer to each other. If all the images are not normalized, this can lead to inconsistencies between scene-to-scene observations over an area for a given day. 

The new target sensor in the harmonization tool allows you to reduce inconsistencies  between data across these sensors and provides temporally and spatially consistent data approximately matching a Sentinel-2 spectral response. If you’d like to learn more about the methodology behind harmonization, read this white paper. 

The new target sensor (Sentinel-2) was designed for agriculture and land cover use cases where users want to use the Dove archive to understand a field's performance and health. For example, users who need to know the health of their crop field can leverage the harmonization tool in order to perform indices calculation (eg, NDVI, NDRE) over their fields. In general, use cases that require using PlanetScope imagery from all sensors in the archive typically require harmonization to achieve time-series and historical analysis. 

Note: the harmonization tool can only be applied to the Surface Reflectance assets in PSScene. 

Users can access this tool within the Orders and Subscriptions API, Planet Explorer, and integrations. 

Orders & Subscriptions API

To harmonize your surface reflectance assets with the Orders and Subscriptions API, use the Harmonization Tool with the “Sentinel-2” as the “target_sensor” attribute value. 

Orders API (Documentation)

{
  "name": "harmonize_example",
  "products": [
    {
      "item_ids": [
        "20211008_002442_03_2456"
      ],
      "item_type": "PSScene",
      "product_bundle": "analytic_sr_udm2"
    }
  ],
  "tools": [
    {
      "harmonize": {
        "target_sensor": "Sentinel-2"
      }
    }
  ]
}

Subscriptions API (Documentation)

{

  "name": "Harmonize PSScene 4-Band SR Subscription",
  "source": {
    "type": "catalog",
    "parameters": {
      "geometry": {
        "coordinates": [
       [[139.5648193359375,35.42374884923695],[140.1031494140625,35.42374884923695],[140.1031494140625, 35.77102915686019], [139.5648193359375,35.77102915686019],
            [139.5648193359375,35.42374884923695]]],"type": "Polygon"},
      "start_time": "2021-03-01T00:00:00Z",
      "end_time": "2022-03-26T00:00:00Z",
      "item_types": ["PSScene"],
      "asset_types": ["ortho_analytic_4b_sr"]
    }
  },
  "tools": [{
      "type": "harmonize",
      "parameters": {
        "target_sensor": "Sentinel-2"
      }
    }
  ],
  "delivery": {
    "type": "google_cloud_storage",
    "parameters": {
      "bucket": "storage-location",
      "credentials": "redacted"
    }
  }
}

Planet Explorer

Integrations