Quality Award Standard 
Important Notice
The Astro Dynamic Quality Awards are a draft standard. The current standard, including awards and naming scheme, is subject to change in the future with the continued help of our collaborators and customers. As of Version 0.1, April 2025, the quality assurance is only applied to Meta Data included in a STAC Item, NOT the assets.
Note
This standard is compatible with STAC 1.0.0 and 1.1.0. We are in the process of updating our documentation to match version 1.1.0.
Overview
As part of Data Sphere's feature set, all data added to the platform will be awarded a Quality Award. The award gives a quick reference for the quality level of a particular data product, enabling users discover the best data for their use case, as well as giving collaborators feed back on the quality of their data.
This document will specify Astro Dynamic's motivations behind providing a quality standard, the current scope of the standard, award criteria for our quality badges, and our future plans.
About
Astro Dynamic's Data Sphere is designed to increase discoverability of earth observation data and its applications to end users, whilst enabling access by anyone at any point in the supply chain. Ease of access and discoverability are key factors in enabling adoption by end users for any earth observation product, and bridging the gap between the space industry and real world applications that has been a decades long challenge.
The STAC Specification has made strides in this respect. Creating a standard that is easy to implement, is human readable, and flexible enough to evolve with the changing needs of the industry. Although, to an end user unfamiliar with frequency bands, nadir, and other fields related earth observation imagery, this meta data does little to help them find the data best suited for their use case. Moreover, having such a flexible framework means that many datasets have significantly different meta data available. From highly detailed collections with a number of STAC Extensions, to only providing the STAC core specification. This can be frustrating for end users and industry alike.
To address these challenges, we use Quality Awards.
The aim of the awards is to provide "assurance at a glance" to users. From one look, a user knows exactly the quality of data and meta data they are getting. We believe this will help to address the gap between industry and real world applications, as well as help in data discovery and enable access to those outside of the space industry.
How it works
Each STAC Item added to Data Sphere will be given an Award. It will be one of the following:
- Unqualified
- Basic
- Bronze
- Silver
- Gold
Each of these awards has a plus variation ( For example, Silver+ ), indicating that there are extensions present which are outside the scope of the award criteria but could still be useful. Whilst each item is being given an award, the item's collection is being updated with the average quality award for all the items in the collection.
These awards are displayed on a contributors collections page as well as on an item's product page. Users are given the option to filter their search results by award.
Rationale
We built the standard on four tenets :
- Simple hierarchy
- Intuitive understanding
- Clear criteria
- Built on existing standards
This is the reason the awards are Basic, Bronze, Silver and Gold. It's a well known ranking, with Gold at the top. Easy and intuitive, and defines clear hierarchy. With the inclusion of the Plus on these awards, it does make the hierarchy less simple. But naturally, a Silver+ or Gold+ would be considered better than a Silver or Gold, without prior knowledge of what the Plus meant.
The Plus helps us keep our award criteria clear as well. It allows us to recognise the usefulness of meta data outside the scope of the awards, and reward the contributors who include more data. Our focus is then maintained on the key fields that our customers and contributors will find most useful. Although we believe that our Awards standard should be widely applicable to many areas of earth observation data, it must maintain a core focus on what the needs of the majority, rather than catering to every use case. This follows the same ideas that the STAC Specification.
As such the awards standard is built on the STAC Specification (as you may have guessed), deriving from the Astro Dynamic STAC Blueprint. Key fields and Extensions were identified after their repeated use in the STAC Index catalogs. Reviewing these fields further, we only included the fields which could be applicable to a wide range of use cases that a majority of users would find useful. This makes it far more accessible and provides simple clear criteria for contributors and users.
Please Note
You are not required to follow the AD STAC Blueprint to be given an award. The Award Standard and Blueprint are two separate documents. The Award Standard is a limited and partial implementation of our Blueprint, focused on items only. There is common ground between the two documents simply because of the recognition of key fields from the STAC Core and Extensions. Thus, following the Blueprint in its entirety would award a contributor a Gold+. Again though, this is not a requirement and you can achieve Gold+ without our Blueprint.
Limitations
The Quality Award Standard is currently a draft standard, and is subject to various changes in the future. Notably, we will be reviewing a change to our current naming and badge awards by version 1.0. Prior to any changes, future draft versions of the standard will be shared in advance with collaborators and customers publicly.
Currently, the scope of the standard only applies to Meta Data included with STAC Items added to Data Sphere. This is only for the inclusion of fields and less on their contents. The quality checker does not asses whether urls given in the Links object or Assets are working or available, except when being shown on the item product page. We will be implementing this type of check as soon as possible, as we recognise this as a important metric that should be checked continually rather than just once. Most checking at this stage of the standard is restricted to checking whether a criteria field is present, and whether the field's type is correct.
Future Plans
As mentioned in the limitations, the Awards Standard only scores the meta data content of a STAC Item, not the assets themselves. This is intentional. Astro Dynamic and Data Sphere are still in their early stages, and the company and product are undergoing continual change. As such, we've kept the version 0.1 of the standard barebones. Thereby, we can develop the standard further in an additive fashion rather than taking out criteria. We hope that this makes it easier for contributors to Data Sphere.
Our aims for the awards extend past simply checking the contents of a STAC Item. In the future, we will be adding in-depth quality assurance to assets as well as verifying all links in an item or collection. This will be introduced as our capabilities grow and as the awards standard matures.
Finally, we appreciate as much feedback as possible on our awards standard. Is it difficult to meet the award criteria? How well do you think this represents your data? Are the awards clear? Are the fields we included in the criteria valid additions? What would you like to see added? Any feedback is greatly appreciated and will help us to build a better standard.
Awards Criteria
There are 6 quality awards to the standard. Higher awards are only given if the previous award criteria have been met. For example, to be awarded a Silver, the item must have met the criteria for a Bronze award. The Plus Award augments every award (apart from unqualified) and is used to identify items with extra meta data outside the scope of the criteria; but could still be useful for a user. Therefore, it is possible to have a Basic+ data product.
The highest award a data product can achieve is Gold+.
| Award | Overview |
|---|---|
| Unqualified | Metadata does not meet the basic level of the Standard or STAC Specification. |
| Basic | Metadata meets the STAC Item specification. |
| Bronze | Metadata contains either the Electro-Optical Extension or SAR Extension. |
| Silver | Metadata has either the View or Projection Extension. |
| Gold | Metadata has either Electro-Optical or SAR Extension, and both the View and Projection Extensions. |
| Plus (+) | Metadata contains extensions that are not included as part of the A.D STAC Specification, or provides its own Metadata in the Assets Object. |
Only fields from a STAC Extension that we consider to be key meta data will be marked as criteria for an Award. Therefore, for a given STAC Extension, only the fields in the award criteria need to be included in the item's meta data. This is aimed to help in cases where not all fields in an extension are necessary, easily available to contributors, or useful to the end user. However, we encourage contributors to fill as many fields as possible for any given Extension.
Basic Criteria
The Basic Award indicates that the item is compliant with the STAC Item Specification version 1.0.0 or higher. A Basic award is required for contributors data to be recommended on Data Sphere.
To be award Basic you will require the following fields from the STAC Item Specification.
| Field | Additional Information |
|---|---|
| stac_version | Version 1.0.0 or higher |
| id | - |
| bbox | - |
| links | Links object containing the at least the root, parent, and self relations. |
| assets | Asset object containing at least one asset with working href. |
| geometry | - |
| datetime | start_datetime and end_datetime can be used in place of datetime. |
| created | - |
| updated | - |
| gsd | - |
| platform | - |
| instruments | Instruments object with at least one instrument. |
Bronze Criteria
Bronze shows that frequency band information for assets is available. There is no criteria for assets to be separated by frequency band, therefore, a single asset may consist of a range of bands.
To be awarded Bronze, either the electro-optical or SAR extension, depending on whether your assets is from optical or SAR instruments.
| Requirement | Additional Information |
|---|---|
| Basic Award | - |
| Electro-Optical Extension | Version 1.1.0 or higher. For optical imagery. Not required for SAR. |
| eo : bands | This should be present in the assets object |
| eo : cloud_cover | Between 0 - 100 |
| SAR Extension | Version 1.0.0 or higher. For SAR imagery. Not required for optical. |
| sar : instrument_mode | - |
| sar : frequency_band | - |
| sar : polarizations | - |
| sar : center_frequency | - |
| sar : resolution_range | - |
| sar : looks_range | - |
Silver Criteria
Silver shows that information for the instrument angles or projection of the assets is available in the item's meta data.
Either the View extension or Projection extension are needed for the Silver award, it is not required to have both.
| Requirement | Additional Information |
|---|---|
| Bronze Award | - |
| View Extension | Version 1.0.0 or higher. |
| view : off_nadir | - |
| view : azimuth | - |
| view : incidence_angle | - |
| Projection Extension | Version 1.1.0 or higher |
| proj : espg / wkt2 / projjson | Only one of these fields is required. |
| proj : shape | - |
| proj : transform | - |
Gold Criteria
Gold shows that all previous awards criteria have been met and the data product contains instrument angle, project, and frequency band information for an item's assets.
All previous awards must be met to be awarded Gold. Must have either the electro-optical or SAR extensions, depending on the asset.
| Requirement | Additional Information |
|---|---|
| Silver Award | - |
| Projection Extension | Version 1.1.0 or higher. Only require fields from previous awards. |
| View Extension | Version 1.0.0 or higher. Only require fields from previous awards. |
| Electro-Optical Extension | Version 1.1.0 or higher. For optical imagery. Not required for SAR. Only require fields from previous awards. |
| SAR Extension | Version 1.0.0 or higher. For SAR imagery. Not required for optical. Only require fields from previous awards. |
Plus
This award is more of an augmentation field to signify to a user that there is extra meta data available on the item that is outside the scope of our quality checks, but could still be useful. Moreover, it is included to reward contributors who provide meta data that is outside of the scope of the standard.
To be awarded a Plus (shown as a "+" on appended to an award, I.e.: Silver+) any additional extensions that are Not Electro-optical, SAR, View, or Projection extensions may be included. Alternatively, it can be a link to meta data in the Assets object, with the role of "metadata" defined in the STAC Item specification.
At least one of these, additional extensions or metadata file, is required to be award a Plus, and there is no limit to the number of extensions or fields in metadata file. Please note, although we do encourage adding as much meta data as possible, there is no additional award for providing more than one extra extension in version 0.1 of the standard.
Example
Here is an example of what a Gold+ item would look like. All the criteria for the Gold Award have been met, and two extra extensions have been included ( remote-data and scientific ), making it Gold+.
{
"stac_version": "1.0.0",
"stac_extensions": [
"https://stac-extensions.github.io/eo/v1.0.0/schema.json",
"https://stac-extensions.github.io/projection/v1.0.0/schema.json",
"https://stac-extensions.github.io/scientific/v1.0.0/schema.json",
"https://stac-extensions.github.io/view/v1.0.0/schema.json",
"https://stac-extensions.github.io/remote-data/v1.0.0/schema.json"
],
"type": "Feature",
"id": "20201211_223832_CS2",
"bbox": [
172.91173669923782,
1.3438851951615003,
172.95469614953714,
1.3690476620161975
],
"geometry": {
"type": "Polygon",
"coordinates": [
[
[
172.91173669923782,
1.3438851951615003
],
[
172.95469614953714,
1.3438851951615003
],
[
172.95469614953714,
1.3690476620161975
],
[
172.91173669923782,
1.3690476620161975
],
[
172.91173669923782,
1.3438851951615003
]
]
]
},
"properties": {
"title": "Example Gold+ Item",
"description": "An example Gold+ awarded item, using the STAC Extended item example as a base",
"datetime": "2020-12-14T18:02:31.437000Z",
"created": "2020-12-15T01:48:13.725Z",
"updated": "2020-12-15T01:48:13.725Z",
"platform": "cool_sat2",
"instruments": [
"cool_sensor_v2"
],
"gsd": 0.66,
"eo:cloud_cover": 1.2,
"proj:epsg": 32659,
"proj:shape": [
5558,
9559
],
"proj:transform": [
0.5,
0,
712710,
0,
-0.5,
151406,
0,
0,
1
],
"view:sun_elevation": 54.9,
"view:off_nadir": 3.8,
"view:azimuth": 2.0,
"view:incidence_angle": 20.1,
"view:sun_azimuth": 135.7,
"rd:type": "scene",
"rd:anomalous_pixels": 0.14,
"rd:earth_sun_distance": 1.014156,
"rd:sat_id": "cool_sat2",
"rd:product_level": "LV3A",
"sci:doi": "10.5061/dryad.s2v81.2/27.2"
},
"collection": "fake_collection_1",
"links": [
{
"rel": "collection",
"href": "./collection.json",
"type": "application/json",
"title": "Simple Example Collection"
},
{
"rel": "root",
"href": "./collection.json",
"type": "application/json",
"title": "Simple Example Collection"
},
{
"rel": "parent",
"href": "./collection.json",
"type": "application/json",
"title": "Simple Example Collection"
},
{
"rel": "alternate",
"type": "text/html",
"href": "http://remotedata.io/catalog/20201211_223832_CS2/index.html",
"title": "HTML version of this STAC Item"
}
],
"assets": {
"analytic": {
"href": "https://storage.googleapis.com/open-cogs/stac-examples/20201211_223832_CS2_analytic.tif",
"type": "image/tiff; application=geotiff; profile=cloud-optimized",
"title": "4-Band Analytic",
"roles": [
"data"
],
"eo:bands": [
{
"name": "band1",
"common_name": "blue",
"center_wavelength": 470,
"full_width_half_max": 70
},
{
"name": "band2",
"common_name": "green",
"center_wavelength": 560,
"full_width_half_max": 80
},
{
"name": "band3",
"common_name": "red",
"center_wavelength": 645,
"full_width_half_max": 90
},
{
"name": "band4",
"common_name": "nir",
"center_wavelength": 800,
"full_width_half_max": 152
}
]
},
"thumbnail": {
"href": "https://storage.googleapis.com/open-cogs/stac-examples/20201211_223832_CS2.jpg",
"title": "Thumbnail",
"type": "image/png",
"roles": [
"thumbnail"
]
},
"visual": {
"href": "https://storage.googleapis.com/open-cogs/stac-examples/20201211_223832_CS2.tif",
"type": "image/tiff; application=geotiff; profile=cloud-optimized",
"title": "3-Band Visual",
"roles": [
"visual"
],
"eo:bands": [
{
"name": "band3",
"common_name": "red",
"center_wavelength": 645,
"full_width_half_max": 90
},
{
"name": "band2",
"common_name": "green",
"center_wavelength": 560,
"full_width_half_max": 80
},
{
"name": "band1",
"common_name": "blue",
"center_wavelength": 470,
"full_width_half_max": 70
}
]
},
"udm": {
"href": "https://storage.googleapis.com/open-cogs/stac-examples/20201211_223832_CS2_analytic_udm.tif",
"title": "Unusable Data Mask",
"type": "image/tiff; application=geotiff;"
},
"json-metadata": {
"href": "http://remotedata.io/catalog/20201211_223832_CS2/extended-metadata.json",
"title": "Extended Metadata",
"type": "application/json",
"roles": [
"metadata"
]
},
"ephemeris": {
"href": "http://cool-sat.com/catalog/20201211_223832_CS2/20201211_223832_CS2.EPH",
"title": "Satellite Ephemeris Metadata"
}
}
}