Key Differences Between UDM2.1 and UDM2.0
UDM2.1 is the latest version developed by Planet, and it significantly improves performance in classifying data when compared to the previous version of the mask, UDM2.0.
These are the key differences between UDM2.0 and UDM2.1:
- There is one haze class rather than two. The Heavy Haze class in UDM2.0 underperformed and was too commonly confused with the Cloud and Light Haze classes. Having a single haze class produces a more consistent and understood product.
- Clouds are defined as interference that are not seen through to the ground and haze is defined as any interference that is seen through to the ground. With this easily understood definition, Planet provides the most usable data.
Note: The formatting of the product has not changed from UDM2.0 to UDM2.1 and is delivered as an 8-band GeoTIFF. The prior Light Haze band (band 4) will be populated with the only Haze value and the values for the Heavy Haze band (band 5) and the heavy_haze_percent metadata will always be 0.
Availability - Date Ranges
Usable Data Masks are available for 4-band PlanetScope imagery back to August 2018 globally and specific agricultural regions back to January 2018. A small percentage of PlanetScope 4-band imagery after August 2018 does not have the UDM2 asset due to rectification and/or image processing failures.
Usable Data Masks are also available for the SkySat archive starting from 2017. In very rare instances, a UDM2 asset may not be available for specific SkySat items. As of November 29, 2023 all new PlanetScope and SkySat imagery will be processed by UDM2.1. Any imagery acquired prior to November 29, 2023 were processed by UDM2.0.
Metadata fields
These metadata fields may be used to construct filters for searching Planet imagery. To learn more, refer to the Planet help page Search Filters.
UDM2.1-related metadata fields
| Field | Type | Value Range | Description |
|---|---|---|---|
| clear_percent | int | [0-100] | Percent of clear values in dataset. Clear values represents scene content areas (non-blackfilled*) that are deemed to be not impacted by cloud, haze, shadow and/or snow. |
| clear_confidence_percent | int | [0-100] | percentage value: per-pixel algorithmic confidence in 'clear' classification |
| cloud_percent | int | [0-100] | Percent of cloud values in the dataset. Cloud values represent regions of a scene (non-blackfilled) that contain thick clouds. You cannot see ground objects through clouds. |
| heavy_haze_percent | int | [0-100] |
Note: UDM2.1 does not include a heavy haze classification. Any non-zero values for this field were generated by the UDM2.0 product. Under UDM2.0’s definition: Percent of heavy haze values in the dataset. Heavy haze values represent scene content areas (non-blackfilled) that contain thin low altitude clouds, higher altitude cirrus clouds, soot and dust which allow fair recognition of land cover features, but not having reliable interpretation of the radiometry or surface reflectance. |
| light_haze_percent | int | [0-100] | Percent of haze values in the dataset. Haze values represent regions of a scene (non-blackfilled) with thin, filamentous clouds, soot, dust, and smoke. You can see ground objects through haze. |
| shadow_percent | int | [0-100] | Percent of cloud shadow values in the dataset. Shadow values represent regions of the scene (non-blackfilled) that are covered by shadows caused by clouds. |
| snow_ice_percent | int | [0-100] | Percent of snow and ice values in the dataset. Snow_ice values represent regions of the scene (non-blackfilled) that are hidden below snow and/or ice. |
| visible_percent | int | [0-100] | Visible values represent the fraction of the scene content (excluding the portion of the image which contains blackfill) which comprises clear, light haze, shadow, snow/ice categories, and is given as a percentage ranging from zero to one hundred. |
| visible_confidence_percent | int | [0-100] | Average of confidence percent for clear_percent, light_haze_percent, shadow_percent and snow_ice_percent |
* Blackfilled content refers to empty regions of a scene file that have no value
UDM2.1 Map Deliverable
The new UDM2.1 asset is delivered as a multi-band GeoTIFF file, with the following bands and values:
UDM2.1 Bands
| Band | Description | Pixel Value Range | Interpretation |
|---|---|---|---|
| Band 1 | Clear map | [0, 1] | 0: not clear, 1: clear |
| Band 2 | Snow map | [0, 1] | 0: no snow or ice, 1: snow or ice |
| Band 3 | Shadow map | [0, 1] | 0: no shadow, 1: shadow |
| Band 4 | Light haze map | [0, 1] | 0: no light haze, 1: light haze |
| Band 5 | Heavy haze map | [0, 1] |
0: no heavy haze, 1: heavy haze Note: UDM2.1 does not support a heavy haze class, but this class name persists to support functional backwards compatibility with UDM2.0. Pixels will never be classified as Heavy Haze with UDM2.1. |
| Band 6 | Cloud map | [0, 1] | 0: no cloud, 1: cloud |
| Band 7 | Confidence map | [0-100] | percentage value: per-pixel algorithmic confidence in classification |
| Band 8 | Unusable pixels | -- | Equivalent to the UDM asset: see Planet's Imagery Specification for complete details |
UDM2.1 Classification Methodology
Planet’s UDM2.1 classification approach is based on supervised machine learning techniques that use observation data from Planet-sensors to train a classification model.
The Planet Engineering team regularly reviews cloud masks and identifies new scenes and add to the truth scene training set. Additionally, your reports of poorly performing scenes or regions are part of the feedback process to improve the truth training set.
To see more details of the classification, please see UDM2.1 Classification Methodology.
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