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| # CEOS-ARD for Radar - Source Data <!-- omit in toc --> | ||
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| - **Scope:** Item, Collection | ||
| - **Extension [Maturity Classification]:** Proposal | ||
| - **Owner**: @m-mohr | ||
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| This extension specifies how to create [STAC] Items for Source Data that | ||
| comply to the [CEOS-ARD product family specifications] (PFS) for radar sensors. | ||
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| > \[!IMPORTANT] | ||
| > See also the [main specification document](radar.md) for CEOS ARD for Radar, | ||
| > which includes the specification for [Product Data](radar.md#stac-items-ard-product). | ||
| > \[!NOTE] | ||
| > This document is a draft and not finalized yet. | ||
| > We welcome feedback from early adopters. | ||
| **Additional resources:** | ||
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| - Examples (ToDo) | ||
| - JSON Schema (ToDo) | ||
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| **Table of Contents:** | ||
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| - [STAC Items (Source Data)](#stac-items-source-data) | ||
| - [Extensions](#extensions) | ||
| - [Common Metadata](#common-metadata) | ||
| - [Processing](#processing) | ||
| - [Projection](#projection) | ||
| - [SAR](#sar) | ||
| - [Satellite](#satellite) | ||
| - [View Geometry](#view-geometry) | ||
| - [Assets](#assets) | ||
| - [Data](#data) | ||
| - [Notes / ToDo](#notes--todo) | ||
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| ## STAC Items (Source Data) | ||
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| Metadata for the source data could also be provided in a different form, | ||
| e.g. in the CEOS ARD XML metadata format or in the source metadata. | ||
| Nevertheless, it is recommended to provide them as STAC Items for a consistent interface. | ||
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| STAC Items must always be valid, but not all STAC Item requirements are covered here, | ||
| only additional requirements and mappings to fulfill the CEOS-ARD requirements are listed here: | ||
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| | Field Name | Req. | Description | | ||
| | --------------- | ----- | ------------------------------------------------------------ | | ||
| | stac_extensions | *n/a* | **REQUIRED.** Must contain [all implemented STAC extensions](radar.md#stac-extensions). | | ||
| | id | 1.6.6 | **REQUIRED.** The source product ID / file name. If another type of ID is provided, the file name can also be extracted from the asset with role `data`. | | ||
| | geometry | 1.6.7 | **REQUIRED.** The geometry of the acquisition in WGS84. | | ||
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| Generally, CEOS-ARD requests to provide DOIs for various resources. | ||
| For STAC, DOIs (e.g. `10.1109/5.771073`) must be converted to URLs (e.g. `https://doi.org/10.1109/5.771073`). | ||
| See [Resolve a DOI name](https://dx.doi.org/) for details. | ||
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| ### Extensions | ||
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| The following [STAC extensions](radar.md#stac-extensions) are relevant for the source Items: | ||
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| | Name | Required | | ||
| | --------------- | :------: | | ||
| | [CEOS-ARD] | ✓ | | ||
| | [Processing] | ✓ | | ||
| | [Projection] | ✓ | | ||
| | [SAR] | ✓ | | ||
| | [Satellite] | ✓ | | ||
| | [View Geometry] | ✗ | | ||
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| Providing the CEOS-ARD [fields](README.md#fields) and [links](README.md#relation-types) fulfills req. 1.3 and 1.4. | ||
| The fields can be provided either in the [Collection](radar.md#stac-collections) or in each Item. | ||
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| ### Common Metadata | ||
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| | Field Name | Req. | Description | | ||
| | ----------- | ----- | ------------------------------------------------------------ | | ||
| | datetime | 1.6.3 | **REQUIRED.** The start date and time of the source data. Can also be expressed as `start_datetime` and `end_datetime` instead. | | ||
| | instruments | 1.6.2 | **REQUIRED.** Instruments in lower-case. | | ||
| | platform | 1.6.2 | **REQUIRED.** Satellite name in lower-case. | | ||
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| Requirement 1.6.2 asks to provide links to: | ||
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| - [CEOS Missions Database] record(s) | ||
| - [CEOS Instruments Database] record(s) | ||
| - [CEOS Measurements Database] record(s) | ||
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| ### Processing | ||
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| | Field Name | Req. | Description | | ||
| | --------------- | ----- | ---------------------------- | | ||
| | processing:facility | 1.6.6 | **REQUIRED.** Processing facility | | ||
| | processing:datetime | 1.6.6 | **REQUIRED.** Processing date and time | | ||
| | processing:software / processing:version | 1.6.6 | **REQUIRED.** Software version(s) | | ||
| | processing:level | 1.6.6 | **REQUIRED.** Processing level | | ||
| | processing:facility | 1.6.6 | **REQUIRED.** Processing facility | | ||
| | processing:facility | 1.6.6 | **REQUIRED.** Processing facility | | ||
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| ### Projection | ||
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| | Field Name | Req. | Description | | ||
| | ------------------------------------- | ----- | ------------------------------------------------------------ | | ||
| | proj:code / proj:wkt2 / proj:projjson | 1.6.7 | **REQUIRED**. Coordinate Reference System (CRS). One of the fields is required to be provided. | | ||
| | proj:bbox | 1.7.7 | **REQUIRED**. The source data geometry in the given CRS. | | ||
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| ### SAR | ||
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| | Field Name | Req. | Description | | ||
| | -------------------- | ----- | ------------------------------------------------------------ | | ||
| | sar:frequency_band | 1.6.4 | **REQUIRED.** Radar band | | ||
| | sar:center_frequency | 1.6.4 | **REQUIRED.** Center frequency | | ||
| | sar:polarizations | 1.6.4 | **REQUIRED.** Polarization(s) | | ||
| | sar:instrument_mode | n/a | **REQUIRED.** Name of the sensor acquisition mode | | ||
| | sar:product_type | n/a | **REQUIRED.** The product type for the source data, e.g. `GRD`. | | ||
| | sar:looks_azimuth | 1.6.6 | **REQUIRED.** Azimuth number of looks | | ||
| | sar:looks_range | 1.6.6 | **REQUIRED.** Range number of looks | | ||
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| ### Satellite | ||
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| | Field Name | Req. | Description | | ||
| | --------------- | ----- | ---------------------------- | | ||
| | sat:orbit_state | 1.6.5 | **REQUIRED.** Pass direction | | ||
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| ### View Geometry | ||
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| | Field Name | Req. | Description | | ||
| | ------------ | ----- | ---------------------- | | ||
| | view:azimuth | 1.6.5 | Platform heading angle | | ||
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| ### Assets | ||
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| **Data Access:** Requirement 1.6.1 **requires** information about data access. | ||
| This requirement is automatically fulfilled by STAC if the referenced assets are publicly accessible. | ||
| If authentication or other steps are required to access the data, this should at least be described in the Collection or Item description. | ||
| For a more machine-readable way implementors could also use other means, such as the [Authentication] extension. | ||
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| **Roles:** The role names specify the values to be used in the Asset's `roles`. | ||
| Each of the assets can either be exposed individually or grouped together in any form. | ||
| In the latter case the role names can simply be merged to a set of unique role names. | ||
| Roles can also be combined for a single file. | ||
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| #### Data | ||
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| For non-metadata requirements that refer to how the data must be created and processed | ||
| please consult the relevant CEOS-ARD specification. | ||
| There can be one or multiple data assets per acquisition. | ||
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| For data assets, the following properties are relavant in the context of CEOS-ARD: | ||
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| | Field Name | Req. | Description | | ||
| | ---------- | --------- | ------------------------------------------------------------ | | ||
| | roles | *various* | **REQUIRED.** All data assets must to include the `data` role. | | ||
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| ## Notes / ToDo | ||
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| - Req. 1.6.4: The following requirements can't be expressed in STAC yet: | ||
| - Observation mode (i.e., Beam mode name) | ||
| - Antenna pointing (Right/Left) | ||
| - Beam ID (i.e., Beam mode Mnemonic) | ||
| - Req. 1.6.5: The orbit data source can't be specified in STAC yet. | ||
| - Req. 1.6.6: STAC can only specify a single value in `sar:looks_range` (i.e. for a single beam), | ||
| but for multiple beams CEOS ARD requires to provide separate values for each beam. | ||
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| [CEOS-ARD product family specifications]: <http://ceos.org/ard/> | ||
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| [CEOS Missions Database]: <https://database.eohandbook.com/database/missiontable.aspx> | ||
| [CEOS Instruments Database]: <https://database.eohandbook.com/database/instrumenttable.aspx> | ||
| [CEOS Measurements Database]: <https://database.eohandbook.com/measurements/overview.aspx> | ||
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| [STAC]: <https://github.com/radiantearth/stac-spec> | ||
| [Maturity Classification]: <https://github.com/radiantearth/stac-spec/tree/master/extensions/README.md#extension-maturity> | ||
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| [Authentication]: <https://github.com/stac-extensions/authentication> | ||
| [CEOS-ARD]: <https://github.com/stac-extensions/ceos-ard> | ||
| [Processing]: <https://github.com/stac-extensions/processing> | ||
| [Projection]: <https://github.com/stac-extensions/projection> | ||
| [SAR]: <https://github.com/stac-extensions/sar> | ||
| [Satellite]: <https://github.com/stac-extensions/sat> | ||
| [View Geometry]: <https://github.com/stac-extensions/view> |
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