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Deprecate sar:product_type in favor of product:type #13

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Jun 20, 2024
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Deprecate sar:product_type in favor of product:type #13

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2 changes: 2 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -14,6 +14,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

### Deprecated

- `sar:product_type` in favor of `product:type`

### Removed

### Fixed
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43 changes: 25 additions & 18 deletions README.md
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Expand Up @@ -36,7 +36,7 @@ To describe frame start and end times, use the
| sar:frequency_band | string | **REQUIRED.** The common name for the frequency band to make it easier to search for bands across instruments. See section "Common Frequency Band Names" for a list of accepted names. |
| sar:center_frequency | number | The center frequency of the instrument, in gigahertz (GHz). |
| sar:polarizations | \[string] | **REQUIRED.** Any combination of polarizations. |
| sar:product_type | string | **REQUIRED.** The product type, for example `SSC`, `MGD`, or `SGC` |
| sar:product_type | string | ***DEPRECATED** in favor of [`product:type`](https://github.com/stac-extensions/product).* The product type, for example `SSC`, `MGD`, or `SGC` |
| sar:resolution_range | number | The range resolution, which is the maximum ability to distinguish two adjacent targets perpendicular to the flight path, in meters (m). |
| sar:resolution_azimuth | number | The azimuth resolution, which is the maximum ability to distinguish two adjacent targets parallel to the flight path, in meters (m). |
| sar:pixel_spacing_range | number | The range pixel spacing, which is the distance between adjacent pixels perpendicular to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type `GRD`. |
Expand All @@ -61,23 +61,6 @@ for instance for `HH+HV` add both `HH` and `HV`.
**Important:** In the `properties` of a STAC Item `sar:polarizations` must be a set with unique elements.
In assets `sar:polarizations` can contain duplicate elements and, if possible, the polarizations must appear in the same order as in the file.

#### sar:product_type

The product type defines the type of processed data contained in the assets. A list of suggestions include:

| sar:product_type | Type | Description |
| ----------------- | --------- | ----------- |
| SSC | complex | Single-look Slant-range Complex image (standard SLC) |
| MGD | amplitude | Multilooked Ground-range Detected image |
| GRD | amplitude | Multilooked Ground-range Detected image (used by Sentinel-1) |
| GEC | amplitude | Geocoded Ellipsoid Corrected image |
| GTC | amplitude | Geocoded Terrain Corrected image |
| RTC | amplitude | Geocoded Radiometrically Terrain Corrected image |
| SGC | complex | Single-look Ground projected Complex image |
| SLC | complex | Single-look Ground projected Complex image (used by Sentinel-1) |

This can vary by data provider, who all may use slightly different names. Sentinel-1 for instance uses `GRD`, which is the same as the more general `MGD` and `SLC` instead of `SGC`.

### Common Frequency Band Names

The `sar:frequency_band` is the name that is commonly used to refer to that band's spectral
Expand All @@ -94,6 +77,30 @@ properties. The table below shows the common name based on the wavelength and fr
| K | 1.1 - 1.7 | 18 - 26.5 | |
| Ka | 0.75 - 1.1 | 26.5 - 40 | |

### Product type

The product type for SAR data defines the type of processed data contained in the assets.
A list of suggestions for [`product:type`](https://github.com/stac-extensions/product) include:

| product:type | Type | Description |
| ------------ | --------- | ----------- |
| SSC | complex | Single-look Slant-range Complex image (standard SLC) |
| MGD | amplitude | Multilooked Ground-range Detected image |
| GRD | amplitude | Multilooked Ground-range Detected image (used by Sentinel-1) |
| GEC | amplitude | Geocoded Ellipsoid Corrected image |
| GTC | amplitude | Geocoded Terrain Corrected image |
| RTC | amplitude | Geocoded Radiometrically Terrain Corrected image |
| SGC | complex | Single-look Ground projected Complex image |
| SLC | complex | Single-look Ground projected Complex image (used by Sentinel-1) |

This can vary by data provider, who all may use slightly different names.
Sentinel-1 for instance uses `GRD`, which is the same as the more general `MGD` and `SLC` instead of `SGC`.

**Note:**
- v1.0 of the extension did require `sar:product_type`.
- v1.1 deprecates `sar:product_type` and it's not required any longer, but `product:type` is **strongly recommended**.
- v2.0 will require `product:type` as part of this extension and remove `sar:product_type`.

### Date and Time

In SAR, you usually have frame start and end time. To describe this information it is recommended to use the [Date and Time Range fields](https://github.com/radiantearth/stac-spec/blob/master/item-spec/common-metadata.md#date-and-time-range).
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5 changes: 3 additions & 2 deletions examples/envisat.json
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Expand Up @@ -2,7 +2,8 @@
"type": "Feature",
"stac_version": "1.0.0",
"stac_extensions": [
"https://stac-extensions.github.io/sar/v1.0.0/schema.json"
"https://stac-extensions.github.io/sar/v1.0.0/schema.json",
"https://stac-extensions.github.io/product/v0.1.0/schema.json"
],
"id": "sar-envisat-example",
"properties": {
Expand All @@ -26,7 +27,7 @@
"sar:looks_azimuth": 4,
"sar:frequency_band": "C",
"sar:center_frequency": 5.331,
"sar:product_type": "GM1_1P"
"product:type": "GM1_1P"
},
"geometry": {
"type": "Polygon",
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5 changes: 3 additions & 2 deletions examples/sentinel-1.json
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Expand Up @@ -2,7 +2,8 @@
"type": "Feature",
"stac_version": "1.0.0",
"stac_extensions": [
"https://stac-extensions.github.io/sar/v1.0.0/schema.json"
"https://stac-extensions.github.io/sar/v1.0.0/schema.json",
"https://stac-extensions.github.io/product/v0.1.0/schema.json"
],
"id": "sentinel-1-example",
"properties": {
Expand All @@ -27,7 +28,7 @@
"sar:looks_equivalent_number": 2.7,
"sar:frequency_band": "C",
"sar:center_frequency": 5.405,
"sar:product_type": "GRD"
"product:type": "GRD"
},
"geometry": {
"type": "Polygon",
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3 changes: 1 addition & 2 deletions json-schema/schema.json
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Expand Up @@ -34,8 +34,7 @@
"required": [
"sar:instrument_mode",
"sar:frequency_band",
"sar:polarizations",
"sar:product_type"
"sar:polarizations"
],
"properties": {
"sar:polarizations": {
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