diff --git a/CHANGELOG.md b/CHANGELOG.md index 5c3e1df..133f05d 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -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 diff --git a/README.md b/README.md index 21574ee..3342bca 100644 --- a/README.md +++ b/README.md @@ -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). | @@ -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