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cloud_cover and snow_cover calculation guidelines (#26)
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* cloud_cover and snow_cover calculation guidelines

Co-authored-by: Matthias Mohr <webmaster@mamo-net.de>
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drnextgis and m-mohr authored Jul 8, 2024
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4 changes: 4 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -28,6 +28,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

- `eo:bands` - use `bands` instead

### Fixed

- Clarified how the coverages `eo:cloud_cover` and `eo:snow_cover` should be computed

## [v1.1.0] - 2023-02-10

### Added
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20 changes: 9 additions & 11 deletions README.md
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Expand Up @@ -40,8 +40,8 @@ The fields in the table below can be used in these parts of STAC documents:

| Field Name | Type | Description |
| ---------------------- | ------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| eo:cloud_cover | number | Estimate of cloud cover, in %. |
| eo:snow_cover | number | Estimate of snow and ice cover, in %. |
| eo:cloud_cover | number | Estimate of cloud cover as a percentage (0-100). |
| eo:snow_cover | number | Estimate of snow and ice cover as a percentage (0-100). |
| eo:common_name | string | The name commonly used to refer to the band to make it easier to search for bands across instruments. See the [list of accepted common names](#common-band-names). |
| eo:center_wavelength | number | The center wavelength of the band, in micrometers (μm). |
| eo:full_width_half_max | number | Full width at half maximum (FWHM). The width of the band, as measured at half the maximum transmission, in micrometers (μm). |
Expand All @@ -51,17 +51,15 @@ The fields in the table below can be used in these parts of STAC documents:

### Coverages

#### eo:cloud_cover
This extension defines some common coverage types (cloud and snow/ice cover) as a percentages (0-100) of the entire scene:
- `eo:cloud_cover`
- `eo:snow_cover`

Estimate of cloud cover as a percentage (0-100) of the entire scene. If not available, the field should not be provided. Generally,
this value should be used in Item Properties rather than Item Assets, as an Item from an electro-optical source is a single snapshot
of the Earth, so the cloud cover value would apply to all assets.
It is important to consider only the valid data regions, excluding any "nodata" areas while calculating both the coverages.
If such information is not available or can't be calculated, the fields should not be provided.

##### eo:snow_cover

Estimate of snow and ice covered surfaces as a percentage (0-100) of the entire scene. If not available, the field should not be provided. Generally,
this value should be used in Item Properties rather than Item Assets, as an Item from an electro-optical source is a single snapshot
of the Earth, so the snow cover value would apply to all assets.
Usually, the properties should be used in Item Properties rather than Item Assets,
as an Item from an electro-optical source is a single snapshot of the Earth, so the coverages usually apply to all assets.

### Spectral Bands

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