CEOS-ARD - Optical - Nighttime Light Surface Radiance

 

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Product Family Specification, Optical, Nighttime Light Surface Radiance

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CEOS Analysis Ready Data Definition

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.

Description

Product Family Specification: Optical, Nighttime Light Surface Radiance (NLSR)

Version: 1.1-draft

Applies to: Data collected by Optical sensors

Background

Data collected with nighttime light sensors operating in the VIS/NIR wavelengths. These typically operate with ground sample distance and resolution in the order of 10-1000m; however, the Specification is not inherently limited to this resolution.

Definitions and Abbreviations

CEOS-ARD
Committee on Earth Observation Satellites - Analysis Ready Data
DOI
Digital Object Identifier
NIR
Near Infrared
NLSR
Nighttime Light Surface Radiance
SI
International System of Units, internationally known by the abbreviation SI (from French Système international d’unités)
VIS
Visible

Requirements

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 Metadata

These 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. Traceability

Identifier: meta.metadata-traceability

Threshold requirements:

Not required.

Goal requirements:

Data must be traceable to SI reference standard.

Notes:

  1. Relationship to Section “Radiometric and Atmospheric Corrections: Measurement Uncertainty”. Traceability requires an estimate of measurement uncertainty.
  2. Information on traceability should be available in the metadata as a single DOI landing page.

2. Source Metadata

These 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 Requirement

Identifier: src.example

This is an example requirement.

Threshold requirements:

This is a threshold requirement.

Goal requirements:

This is a goal requirement.

Notes:

  1. This is a note.

3. Product Metadata

Information related to the CEOS-ARD product generation procedure and geographic parameters.

3.1. Example Requirement

Identifier: prd.example

This is an example requirement.

Threshold requirements:

This is a threshold requirement.

Goal requirements:

This is a goal requirement.

Notes:

  1. This is a note.

4. Per-Pixel Metadata

The 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 Requirement

Identifier: pxl.example

This is an example requirement.

Threshold requirements:

This is a threshold requirement.

Goal requirements:

This is a goal requirement.

Notes:

  1. This is a note.

5. Radiometric and Atmospheric Corrections

The 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 Uncertainty

Identifier: 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.

Threshold requirements:

Not required.

Goal requirements:

An estimate of the certainty of the values is provided in measurement units.

Notes:

  1. This is a requirement for SI traceability. See also Section “General Metadata: Traceability”.
  2. Information on measurement uncertainty should be available in the metadata as a single DOI landing page.

6. Geometric Corrections

The 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 Requirement

Identifier: gcor.example

This is an example requirement.

Threshold requirements:

This is a threshold requirement.

Goal requirements:

This is a goal requirement.

Notes:

  1. This is a note.

Introduction

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.

What is CEOS Analysis Ready Data?

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.

When can a product be called CEOS-ARD?

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.

What is the difference between Threshold and Goal?

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.

References

International Organization for Standardization. 2009. “Geographic information — Metadata — Part 2: Extensions for imagery and gridded data.” Standard. Geneva, CH: International Organization for Standardization.
Mills, Stephen, and Steven Miller. 2014. “VIIRS Day-Night Band (DNB) Calibration Methods for Improved Uniformity.” Proceedings of SPIE - The International Society for Optical Engineering 9218 (October): 921809. https://doi.org/10.1117/12.2060143.
Román, Miguel O., Zhuosen Wang, Qingsong Sun, Virginia Kalb, Steven D. Miller, Andrew Molthan, Lori Schultz, et al. 2018. “NASA’s Black Marble Nighttime Lights Product Suite.” Remote Sensing of Environment 210: 113–43. https://doi.org/https://doi.org/10.1016/j.rse.2018.03.017.
Ryan, Robert E., Mary Pagnutti, Kara Burch, Larry Leigh, Timothy Ruggles, Changyong Cao, David Aaron, Slawomir Blonski, and Dennis Helder. 2019. “The Terra Vega Active Light Source: A First Step in a New Approach to Perform Nighttime Absolute Radiometric Calibrations and Early Results Calibrating the VIIRS DNB.” Remote Sensing 11 (6). https://doi.org/10.3390/rs11060710.
Wang, Zhuosen, Miguel O. Román, Virginia L. Kalb, Steven D. Miller, Jianglong Zhang, and Ranjay M. Shrestha. 2021. “Quantifying Uncertainties in Nighttime Light Retrievals from Suomi-NPP and NOAA-20 VIIRS Day/Night Band Data.” Remote Sensing of Environment 263: 112557. https://doi.org/https://doi.org/10.1016/j.rse.2021.112557.