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Merge pull request #18 from stac-extensions/swath
Add SAR swath information
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‎CHANGELOG.md

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@@ -8,6 +8,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
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### Added
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- `sar:beam_ids` property to describe the swath in the SAR acquisition.
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### Changed
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- Required properties of type `string` require a minimum length of `1`.

‎README.md

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- Examples:
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- [Envisat](examples/envisat.json)
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- [Sentinel-1](examples/sentinel-1.json)
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- [Sentinel-1 GRD EW](examples/sentinel-1-grd-ew.json)
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- [Sentinel-1 GRD S4](examples/sentinel-1-grd-s4.json)
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- [Sentinel-1 SLC IW](examples/sentinel-1-slc-iw.json)
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- [JSON Schema](json-schema/schema.json)
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- [Changelog](./CHANGELOG.md)
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## Item Properties or Asset Fields
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| Field Name | Type | Description |
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| --------------------------- | --------- | ------------------------------------------------------------ |
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| Field Name | Type | Description |
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| --------------------------- | --------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
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| sar:instrument_mode | string | **REQUIRED.** The name of the sensor acquisition mode that is commonly used. This should be the short name, if available. For example, `WV` for "Wave mode" of Sentinel-1 and Envisat ASAR satellites. |
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| 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. |
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| sar:center_frequency | number | The center frequency of the instrument, in gigahertz (GHz). |
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| sar:polarizations | \[string] | **REQUIRED.** Any combination of polarizations. |
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| 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` |
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| 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). |
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| 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). |
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| 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`. |
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| sar:pixel_spacing_azimuth | number | The azimuth pixel spacing, which is the distance between adjacent pixels parallel to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type `GRD`. |
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| sar:looks_range | number | Number of range looks, which is the number of groups of signal samples (looks) perpendicular to the flight path. |
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| sar:looks_azimuth | number | Number of azimuth looks, which is the number of groups of signal samples (looks) parallel to the flight path. |
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| sar:looks_equivalent_number | number | The equivalent number of looks (ENL). |
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| sar:observation_direction | string | Antenna pointing direction relative to the flight trajectory of the satellite, either `left` or `right`. |
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| 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. |
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| sar:center_frequency | number | The center frequency of the instrument, in gigahertz (GHz). |
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| sar:polarizations | \[string] | **REQUIRED.** Any combination of polarizations. |
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| 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` |
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| 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). |
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| 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). |
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| 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`. |
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| sar:pixel_spacing_azimuth | number | The azimuth pixel spacing, which is the distance between adjacent pixels parallel to the flight path, in meters (m). Strongly RECOMMENDED to be specified for products of type `GRD`. |
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| sar:looks_range | number | Number of range looks, which is the number of groups of signal samples (looks) perpendicular to the flight path. |
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| sar:looks_azimuth | number | Number of azimuth looks, which is the number of groups of signal samples (looks) parallel to the flight path. |
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| sar:looks_equivalent_number | number | The equivalent number of looks (ENL). |
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| sar:observation_direction | string | Antenna pointing direction relative to the flight trajectory of the satellite, either `left` or `right`. |
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| sar:relative_burst | number | Identification number that uniquely identifies a burst cycle within each repeat cycle. |
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| sar:beam_ids | \[string] | Composition of the swath of the SAR acquision referencing the beam identifiers. |
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**Note:** In this specification *range* values are meant to be measured perpendicular to the flight path and *azimuth* values
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are meant to be measured parallel to the flight path.
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**Important:** In the `properties` of a STAC Item `sar:polarizations` must be a set with unique elements.
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In assets `sar:polarizations` can contain duplicate elements and, if possible, the polarizations must appear in the same order as in the file.
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#### sar:beam_ids
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The `sar:beam_ids` field is used to reference the beam identifiers of the SAR acquisition. According to the mission and the sensor mode,
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the beam identifiers can be used to identify the composition of the swath of the SAR acquisition.
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The beam identifiers are usually provided in the metadata of the SAR data.
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### Common Frequency Band Names
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The `sar:frequency_band` is the name that is commonly used to refer to that band's spectral
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properties. The table below shows the common name based on the wavelength and frequency ranges for several SAR satellites.
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| Common Name | Wavelength Range (cm) | Frequency Range (GHz) | Satellites |
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| ----------- | --------------------- | --------------------- | ---------- |
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| P | 30 - 120 | 0.25 - 1 | |
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| L | 15 - 30 | 1 - 2 | ALOS, JERS, NISAR, SOACOM |
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| S | 7.5 - 15 | 2 - 4 | HJ-1C |
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| C | 3.8 - 7.5 | 4 - 8 | EnviSat, ERS, Radarsat, Risat-1, Sentinel-1 |
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| Common Name | Wavelength Range (cm) | Frequency Range (GHz) | Satellites |
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| ----------- | --------------------- | --------------------- | -------------------------------------------------- |
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| P | 30 - 120 | 0.25 - 1 | |
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| L | 15 - 30 | 1 - 2 | ALOS, JERS, NISAR, SOACOM |
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| S | 7.5 - 15 | 2 - 4 | HJ-1C |
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| C | 3.8 - 7.5 | 4 - 8 | EnviSat, ERS, Radarsat, Risat-1, Sentinel-1 |
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| X | 2.4 - 3.8 | 8 - 12.5 | Cosmo-SkyMed, TerraSAR-X, TanDEM-X, PAZ, KOMPSat-5 |
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| Ku | 1.7 - 2.4 | 12.5 - 18 | |
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| K | 1.1 - 1.7 | 18 - 26.5 | |
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| Ka | 0.75 - 1.1 | 26.5 - 40 | |
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| Ku | 1.7 - 2.4 | 12.5 - 18 | |
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| K | 1.1 - 1.7 | 18 - 26.5 | |
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| Ka | 0.75 - 1.1 | 26.5 - 40 | |
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### Product type
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The product type for SAR data defines the type of processed data contained in the assets.
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A list of suggestions for [`product:type`](https://github.com/stac-extensions/product) include:
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| product:type | Type | Description |
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| ------------ | --------- | ----------- |
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| SSC | complex | Single-look Slant-range Complex image (standard SLC) |
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| MGD | amplitude | Multilooked Ground-range Detected image |
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| GRD | amplitude | Multilooked Ground-range Detected image (used by Sentinel-1) |
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| GEC | amplitude | Geocoded Ellipsoid Corrected image |
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| GTC | amplitude | Geocoded Terrain Corrected image |
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| RTC | amplitude | Geocoded Radiometrically Terrain Corrected image |
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| SGC | complex | Single-look Ground projected Complex image |
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| product:type | Type | Description |
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| ------------ | --------- | --------------------------------------------------------------- |
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| SSC | complex | Single-look Slant-range Complex image (standard SLC) |
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| MGD | amplitude | Multilooked Ground-range Detected image |
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| GRD | amplitude | Multilooked Ground-range Detected image (used by Sentinel-1) |
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| GEC | amplitude | Geocoded Ellipsoid Corrected image |
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| GTC | amplitude | Geocoded Terrain Corrected image |
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| RTC | amplitude | Geocoded Radiometrically Terrain Corrected image |
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| SGC | complex | Single-look Ground projected Complex image |
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| SLC | complex | Single-look Ground projected Complex image (used by Sentinel-1) |
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This can vary by data provider, who all may use slightly different names.
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This list should not be considered definitive, and implementors are welcome to use other asset roles. If consensus and tooling consolidates around
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these role names then they will be specified in the future as more standard than just 'best practices'.
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| Role Name | Description |
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| --------- | ---------------------------------------------------------------------- |
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| local-incidence-angle | Points to the local incidence angle file. |
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| ellipsoid-incidence-angle | Points to the ellipsoid incidence angle file. |
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| noise-power | Points to the noise power file. |
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| amplitude | Points to the intensity file with focused SAR data that has been ground range detected (e.g. GRD). |
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| magnitude | Points to the intensity file where data are represented as complex numbers containing amplitude and phase information (e.g SLC). |
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| sigma0 | Points to the radar backscatter file where data is referenced in ground surface. It is often derived from an `amplitude` or a `magnitude` role asset. |
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| beta0 | Points to the radar backscatter file where data is referenced in the slant range plane and is radiometrically calibrated. It is often derived from an `amplitude` or a `magnitude` role asset. |
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| gamma0 | Points to the radar backscatter file where data is referenced in the plane perpendicular to the line of sight. It is often derived from an `amplitude` or a `magnitude` role asset. |
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| date-offset | Points to the date-offset file. |
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| covmat | Points to the Points to the Normalized Polarimetric Radar Covariance Matrix (CovMat) file. |
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| prd | Points to the Polarimetric Radar Decomposition (PRD) file. |
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| Role Name | Description |
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| ------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| local-incidence-angle | Points to the local incidence angle file. |
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| ellipsoid-incidence-angle | Points to the ellipsoid incidence angle file. |
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| noise-power | Points to the noise power file. |
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| amplitude | Points to the intensity file with focused SAR data that has been ground range detected (e.g. GRD). |
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| magnitude | Points to the intensity file where data are represented as complex numbers containing amplitude and phase information (e.g SLC). |
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| sigma0 | Points to the radar backscatter file where data is referenced in ground surface. It is often derived from an `amplitude` or a `magnitude` role asset. |
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| beta0 | Points to the radar backscatter file where data is referenced in the slant range plane and is radiometrically calibrated. It is often derived from an `amplitude` or a `magnitude` role asset. |
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| gamma0 | Points to the radar backscatter file where data is referenced in the plane perpendicular to the line of sight. It is often derived from an `amplitude` or a `magnitude` role asset. |
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| date-offset | Points to the date-offset file. |
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| covmat | Points to the Points to the Normalized Polarimetric Radar Covariance Matrix (CovMat) file. |
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| prd | Points to the Polarimetric Radar Decomposition (PRD) file. |
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## Contributing
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‎examples/sentinel-1.json renamed to ‎examples/sentinel-1-grd-ew.json

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"sar:looks_equivalent_number": 2.7,
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"sar:frequency_band": "C",
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"sar:center_frequency": 5.405,
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"sar:beam_ids": [
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"EW"
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],
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"product:type": "GRD"
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},
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"geometry": {

‎examples/sentinel-1-grd-s4.json

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{
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"type": "Feature",
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"stac_version": "1.0.0",
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"stac_extensions": [
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"https://stac-extensions.github.io/sar/v1.0.0/schema.json",
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"https://stac-extensions.github.io/sat/v1.0.0/schema.json",
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"https://stac-extensions.github.io/processing/v1.2.0/schema.json",
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"https://stac-extensions.github.io/product/v0.1.0/schema.json"
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],
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"id": "S1A_S4_GRDH_1SDV_20240531T073124_20240531T073144_054112_06947D_072C",
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"collection": "SENTINEL-1",
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"geometry": {
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"type": "Polygon",
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"coordinates": [
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[
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[
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-24.488338,
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],
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[
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-24.251352,
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15.285328
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],
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[
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-24.985012,
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15.424737
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],
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[
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-25.217945,
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14.262449
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],
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[
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-24.488338,
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]
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]
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]
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},
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"bbox": [
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-25.217945,
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14.122218,
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-24.251352,
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15.424737
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],
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"properties": {
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"sat:absolute_orbit": 54112,
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"sat:orbit_state": "descending",
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"processing:datetime": "2024-05-31T11:25:04.541000+00:00",
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"sar:instrument_mode": "SM",
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"processing:level": "L1",
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"sar:beam_ids": [
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"S4"
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],
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"processing:facility": "Production Service-SERCO",
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"processing:version": "003.71",
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"constellation": "sentinel-1",
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"Instruments": [
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"SAR"
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],
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"sat:relative_orbit": 140,
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"sar:polarizations": [
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"VV",
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"VH"
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],
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"platforn": "sentinel-1a",
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"datetime": "2024-05-31T07:31:24.961Z",
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"end_datetime": "2024-05-31T07:31:44.204Z",
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"start_datetime": "2024-05-31T07:31:24.961Z",
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"product:type": "S4_GRDH_1S-COG",
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"sar:frequency_band": "C"
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},
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"assets": {
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"vh": {
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"href": "https://example.com/collections/sentinel-1/items/S1A_S4_GRDH_1SDV_20240531T073124_20240531T073144_054112_06947D_072C/assets/s1a-s4-grd-vh-20240531t073124-20240531t073144-054112-06947d-002-cog.tiff",
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"type": "image/tiff; application=geotiff; profile=cloud-optimized",
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"title": "VH Band",
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"sar:polarizations": [
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"VH"
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]
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},
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"vv": {
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"href": "https://example.com/collections/sentinel-1/items/S1A_S4_GRDH_1SDV_20240531T073124_20240531T073144_054112_06947D_072C/assets/s1a-s4-grd-vv-20240531t073124-20240531t073144-054112-06947d-001-cog.tiff",
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"type": "image/tiff; application=geotiff; profile=cloud-optimized",
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"title": "VV Band",
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"sar:polarizations": [
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"VV"
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]
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},
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"thumbnail": {
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"href": "https://example.com/collections/sentinel-1/items/S1A_S4_GRDH_1SDV_20240531T073124_20240531T073144_054112_06947D_072C/assets/s1a-s4-grd-thumbnail-20240531t073124-20240531t073144-054112-06947d-072c.png",
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"type": "image/png",
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"title": "Thumbnail"
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}
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},
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"links": [
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{
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"rel": "root",
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"href": "../../catalog.json",
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"type": "application/json"
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},
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{
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"rel": "collection",
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"href": "../collection.json",
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"type": "application/json"
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}
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]
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}

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