Liping Di Laboratory for Advanced Information Technology and Standards (LAITS)

1. The Planned ISO TC 211 Standard Project on Radiometric Calibration and Validation of Remote Sensing Data Liping Di Laboratory for Advanced Information Technology and Standards (LAITS) George Mason University 9801 Greenbelt Road, Suite 316-317 Lanham, MD 20706 lpd@rattler.gsfc.nasa.gov

2. Introduction • Remote sensing is one of the major methods for collecting geospatial data. • Both public and private sectors have been involved in the remote sensing activities. • Remote sensing data have been widely used in all aspects of human socio-economic activities, ranging from the global change research to decision making. • Those research and applications normally requires data collected by multiple sensors and provided by different data providers. • Those data are normally analyzed by users through GIS/Image process systems to derive useful information. • Without basic standards for remote sensing data and system, it is very difficult to • integrate data from multiple sources, • share data among the data providers and users, • interoperate between data systems.

3. The ISO TC211 • A technical committee of the International Organization for Standardization (ISO), responsible for setting international standards on geographic information. • Since 1997, ISO TC 211 has been worked on developing international standards in the area of the imagery and gridded data, which includes remote sensing data. • ISO 19121-Imagery and Grid Data • ISO 19124-Imagery and gridded data components • ISO 19129-Imagery, gridded and coverage data framework • ISO 19130-Sensor and data models for imagery and gridded data • ISO 19115.2-Metadata: Extensions for imagery and gridded data • ISO 19101.2-Reference Model: Imagery • Planned new TC211 projects on remote sensing • Radiometric calibration and validation for remote sensing data. • Rules for encoding imagery and gridded data.

4. Categories of remote sensing data • There are two major types of properties in remote sensing data. • Geometric. • Contents. • Based on geometric properties, remote sensing data can be classified into two major categories: • Georeferenceable: ungeorectified remote sensing data such as swath data. • Georectified (include ortho-rectified). • Based on their contents, remote sensing data can be categorized into: • Images – the cell value subject to interpretation for its geographic/geophysical meanings. • Thematic gridded data-geographic meaning assigned. • The ISO 19130 standardizes the geometric aspects of georeferenceable remote sensing data. • Defined sensor models and data model.

5. ISO 19130-Sensor and Data Models for Imagery and Gridded Data • It specifies a sensor model describing the physical and geometrical properties of each kind of photogrammetric, remote sensing and other sensors that produces imagery type of data. • It defines a conceptual data model that specifies, for each kind of sensor, the minimum content requirement and the relationship among the components of the content for the raw data that was measured by the sensor and provided in an instrument-based coordinate system, to make it possible to geolocate and analyze the data. • The standard defines the ways for providing the geolocation information, but not the geolocation methods itself. • Currently experts from eleven countries and five international organizations form the project team. • Australia, Canada, France, Germany, Japan, Malaysia, Saudi Arabia, South Africa, South Korea, Thailand, USA. • OGC, CEOS, IHO, DGIWG, and ISPRS. • The FGDC Swath Standard is the basis for the data model part of the standard.

6. Data Model for Georefereable Dataset • ISO 19130 defines a data model for georefereable datasets. The top level UML model is shown:

7. The needs for the radiometric standard • Standardizing the description of radiometric properties of remote sensing data is very important for data utilization and sharing. • Both in ISO 19115- Geographic metadata and in ISO 19130 sensor and data models, there is a placeholder for radiometric class. • No further definitions were specified. • There is no standard in ISO to specify the radiometric properties and radiometric calibrations of remote sensing data. • The ISO TC 211 WG 6 realized the importance of standardizing the radiometric properties of remote sensing data • It started to discuss the needs for such standards in Year 2002. • WG6 briefed the plan for an ISO standard project on radiometric calibration and validation of remote sensing data at ISO TC211 Plenary in May 2003. • WG6 authorized the ISO 19130 project team to start the preparatory work on the subject at the same time.

8. The Preparatory Work • An ISO standard project typically has the following stages: • Proposal, Working Draft (WD), Committee Draft (CD), Draft International Standard (DIS), Formal Draft International Standard (FDIS), and International Standard (IS). • The main tasks for the preparatory work are: • Prepare a new work item proposal (NWIP) for the new project. • Inform the possible stakeholders the planned new ISO project. • Dr. Liping Di of GMU, the chair of ISO 19130, took the lead for preparing the new work item proposal. • A draft NWIP has been prepared and was briefed at the ISO TC WG6 meeting in Berlin in October 2003. • It is planned the proposal will be submitted to ISO TC 211 by U.S. national body as a U.S. Contribution. • A project team will be formed once the proposal is approved by ISO TC 211. • The project team consists of a project chair, an editor, and experts nominated by the members and liaison organizations of the TC. • It is expected the U.S. will submit the proposal to ISO TC 211.

9. The Scope • The tentative title for the new ISO standard project is: Geographic Information- Radiometric calibration and validation of remotely sensed data. • The standard covers two groups of remote sensing data: • Radiometrically un-calibrated data (e.g., data still in sensor reading as DN) • Radiometrically calibrated data (e.g., radiance), but not the thematic data. • For the un-calibrated data, • For each type of remote sensing sensors, the standard defines all necessary parameters required to quantitatively derive physical values from raw sensor measurements and evaluate their quality. • The standard specifies the information that is needed to define the response of the system to input signals. • For calibrated data, • The standard defines the ways for reporting the methods for the radiometric calibration/correction, the accuracy and precision of the calibration, and the methods for determining the accuracy and precision.

10. Purpose • The purpose of this International Standard is to define standard content that is necessary for the radiometric calibration of sensors measurements and the validation of the results. • An essential aspect of deriving geographical information from sensor measurements is the conversion of the raw data values into physical variables that can be interpreted in the context of geographical information. To be able to do so, the instrument must be calibrates: its radiometric properties and its response to input signals must be known. This standard will define the precise information that must be provided if this process is to be carried out for different kinds of measuring systems.

11. The Content of the Standard • The current thoughts on the content of the standards envision two parts. • The first part will define, for each type of sensors, the terms and definitions for the parameters and their quality measurements required for the radiometric correction of raw remote sensing data products acquired by the type of sensors. • The second part will define the methodology for reporting the radiometric correction and validation procedures and the radiometric fidelity of radio-metrically corrected remote sensing data.

12. Sensor classification • For the purpose of this standard, remote sensors are grouped into two groups: • active sensors • passive sensors • Each group of sensors will further classify into five types based on the wavelength the sensor works • visible/near infrared (optical), thermal infrared, microwave, radio wave, sound wave. • A remote sensing instrument may have multiple bands working on different wavelength, each band is considered as a sensor. • The standard will focus on optical, thermal, and microwave, both active and passive.

13. Cooperative development of the standard • A standard setting process is a consensus-building process. • A successful standard should be developed by as many stakeholders as possible. • Because of the importance of this planned standard to the remote sensing, the international remote sensing community should participate fully in the development of standard. • The International Society for Photogrammetry and Remote Sensing (ISPRS), • The Committee on Earth Observation Satellites (CEOS). • The IEEE Geoscience and Remote Sensing Society (IGARSS) • The International workshop on Radiometric and Geometric Calibration organized by the ISPRS/CEOS joint task force is the important venue for reporting the best international practices on radiometric and geometric calibration. • ISOTC 211 expects that results of this workshop will serve as one of the information sources for drafting the international standards. It also expect the above mentioned international organizations will be the major force for setting the standard.