Product Family Specification, Optical, Surface Reflectance
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CEOS Analysis Ready Data (CEOS-ARD) are satellite data that have been processed to a minimum set of requirements and organized into a form that allows immediate analysis with a minimum of additional user effort and interoperability both through time and with other datasets.
Product Family Specification: Optical, Surface Reflectance (SR)
Version: 5.1-draft
Applies to: Data collected by Optical sensors
Data collected with multispectral optical sensors operating in the VIS/NIR/SWIR wavelengths at all ground sample distances and resolutions.
WARNING: The requirement numbers below are not stable and may change or may be removed at any time. Do not use the numbers to refer back to specific requirements! Instead, use the textual identifier that is provided in brackets directly after the title.
1.
General MetadataThese are metadata records describing a distributed collection of pixels. The collection of pixels referred to must be contiguous in space and time. General metadata should allow the user to assess the overall suitability of the dataset, and must meet the requirements listed below.
1.1.
TraceabilityIdentifier: meta.metadata-traceability
Not required.
Data must be traceable to SI reference standard.
Notes:
2.
Source MetadataThese are metadata records describing (detailing) each acquisition (source data) used to generate the ARD product. This may be one or mutliple acquisitions.
2.1.
Example RequirementIdentifier: src.example
This is an example requirement.
This is a threshold requirement.
This is a goal requirement.
Notes:
3.
Product MetadataInformation related to the CEOS-ARD product generation procedure and geographic parameters.
3.1.
Example RequirementIdentifier: prd.example
This is an example requirement.
This is a threshold requirement.
This is a goal requirement.
Notes:
4.
Per-Pixel MetadataThe following minimum metadata specifications apply to each pixel. Whether the metadata are provided in a single record relevant to all pixels or separately for each pixel is at the discretion of the data provider. Per-pixel metadata should allow users to discriminate between (choose) observations on the basis of their individual suitability for applications.
Cloud optimized file formats are recommended.
4.1.
Example RequirementIdentifier: pxl.example
This is an example requirement.
This is a threshold requirement.
This is a goal requirement.
Notes:
5.
Radiometric and Atmospheric CorrectionsThe following requirements must be met for all pixels in a collection. The requirements indicate both the necessary outcomes and the minimum steps necessary to be deemed to have achieved those outcomes. Radiometric corrections must lead to a valid measurement of surface reflectance.
5.1.
Measurement UncertaintyIdentifier: rac.measurements-uncertainty
Note: In current practice, users determine fitness for purpose based on knowledge of the lineage of the data, rather than on a specific estimate of measurement uncertainty.
Not required.
An estimate of the certainty of the values is provided in measurement units.
Notes:
6.
Geometric CorrectionsThe geometric corrections are steps that are taken to place the measurement accurately on the surface of the Earth (that is, to geolocate the measurement) allowing measurements taken through time to be compared. This section specifies any geometric correction requirements that must be met in order for the data to be analysis ready.
6.1.
Example RequirementIdentifier: gcor.example
This is an example requirement.
This is a threshold requirement.
This is a goal requirement.
Notes:
This section aims to provide background and specific information on the processing steps that can be used to achieve analysis ready data for a specific and well-developed Product Family Specification. This Guidance material does not replace or override the specifications.
CEOS-ARD are products that have been processed to a minimum set of requirements and organized into a form that allows immediate analysis with a minimum of additional user effort. In general, these products would be resampled onto a common geometric grid (for a given product) and would provide baseline data for further interoperability both through time and with other datasets.
CEOS-ARD products are intended to be flexible and accessible products suitable for a wide range of users for a wide variety of applications, including particularly time series analysis and multi-sensor application development. They are also intended to support rapid ingestion and exploitation via high-performance computing, cloud computing and other future data architectures. They may not be suitable for all purposes and are not intended as a replacement for other types of satellite products.
The CEOS-ARD branding is applied to a particular product once:
Agencies or other entities considering undertaking an assessment process should consult the CEOS-ARD Governance Framework.
A product can continue to use CEOS-ARD branding as long as its generation and distribution remain consistent with the peer-reviewed assessment.
Threshold (Minimum) requirements are the minimum that is needed for the data to be analysis ready. This must be practical and accepted by the data producers.
Goal (Desired) requirements (previously referred to as “Target”) are the ideal; where we would like to be. Some providers may already meet these.
Products that meet all threshold requirements should be immediately useful for scientific analysis or decision-making.
Products that meet goal requirements will reduce the overall product uncertainties and enhance broad-scale applications. For example, the products may enhance interoperability or provide increased accuracy through additional corrections that are not reasonable at the threshold level.
Goal requirements anticipate continuous improvement of methods and evolution of community expectations, which are both normal and inevitable in a developing field. Over time, goal specifications may (and subject to due process) become accepted as threshold requirements.