JOINT ISPRS/CEOS-WGCV TASK FORCE
ON RADIOMETRIC AND GEOMETRIC CALIBRATION
S.A. Morain?, V.M. Zanoni^
“UNM, Earth Data Analysis Center, Albuquerque, New Mexico, 87111 - (smorain@edac.unm.edu)
"Earth Science Applications Directorate, NASA, Stennis Space Center, Mississippi 39529 - (vicki.m.zanoni@nasa.gov)
Commission I, WG 1/2
KEY WORDS: Radiometry, Calibration, Measurement, Instruments, Parameters, Standards, Targets, Performance
ABSTRACT:
A draft Resolution passed by the Committee on Earth Observing Satellites (CEOS) Plenary in 2002 recommended that a task force
be established with joint membership by the Working Group on Calibration and Validation (WGCV) and ISPRS. This resolution
formed the basis for subsequent ISPRS Resolutions (1.1, 1.2, and 1.3) adopted by the General Assembly at the XIX" Congress in
Amsterdam. The idea originated from the CEOS WGCV Terrain Mapping Subgroup, whiclf recognized that a standard format for
sensor parameters should be established. There is a demand for consistent practices in measuring the radiometric and geometric
calibration of satellite sensor data because of: (1) the rapid increase in numbers of orbital and Earth-oriented platforms, (2) the
variety of digital sensors now taking Earth and environmental measurements across the EM spectrum, (3) the wide array of angular
and multi-angular measurements and fields-of-view being employed, (4) the desire for measurements and observations to be fused
into complex products for specific applications, and (5), the growing interest by Ordinary Members of ISPRS to contribute high
quality calibration test fields for global sensors that embrace all of the world's ecological and climate zones. ISPRS Working Groups
I/1, 1/2 and I/5 have responsibility for task force activities. In January 2001, the WGs developed a profile of expertise and skills
required by the task force. In November 2002, the first joint task force meeting was held in Denver at the Commission-I midterm
symposium to identify its Chair and membership. Most recently, in December 2003, the Task Force convened its first International
Workshop to identify, define, and review best practices for measuring the radiometric and geometric properties of infrared and
visible optical sensors (IVOS). This paper is a summary of the workshop findings and recommendations. For further information on
calibration methods, techniques, and best practices, a peer-reviewed book in the ISPRS Book Series titled Post-launch Calibration
of Satellite Sensors contains articles by most of the Workshop presenters. It is scheduled for release in summer 2004.
physical and cultural systems. To perform their individual
Missions, these sensors have a variety of system designs,
spectral bandwidths, and spatial resolutions. These various data
sets are being fused into digital composites, and applied in a
1. BACKGROUND
1.1 Rationale
Digital aerial and satellite image data are acquired as raster
(gridded) data. For optical systems, the dimensions of a picture
clement are defined by the: (a) altitude of the sensor, (b)
milliradian field-of-view, (c¢) number and arrangement of
detectors, and (d) system's instantaneous-field-of-view. Digital
values for each picture element are determined by the radiance
recorded for given spectral bands and the radiometric resolution
(bit rate).
On a global scale, images derived from digital systems are
useful for studying Earth processes because they reveal
synoptic patterns that would otherwise never be observable in a
timely fashion to capitalize on their content. Science and user
communities are well trained to make visual interpretations of
synoptic images related to terrestrial vegetation,
geomorphology and digital elevation models, ocean patterns
(temperature, chlorophyll), ice, and many atmospheric
constituents. Experience and expanded data availability from an
increasing number of sensors operated by both national
governments and commercial firms, have expanded applications
requiring electronic fusion of many data sets for use at local and
regional scales.
Trends in the New Millennium are to fuse data from several
sensors designed to measure different phenomena of the Earth's
modelling framework to local and regional needs. Interpretation
of multi-layered and multi-theme natural and cultural processes
requires a comprehensive understanding of the radiometric and
geometric properties of each of the input data sets forming the
composite because misinterpretation of the modelled results can
carry critical social, economic, and political implications.
1.2 Actions Undertaken
In anticipation of the greater depth of understanding required to
interpret fused images and modelled results from sensor data,
the Committee on Earth Observing Satellites (CEOS)
recognized a need for consistency in terminology and
definitions for radiometric and geometric calibration
parameters. The International Society for Photogrammetry and
Remote Sensing (ISPRS) likewise recognized this need,
especially on behalf of global data users who might otherwise
misinterpret data products, or interpret them in inconsistent
fashion. The two organizations therefore formed a joint Task
Force on Radiometric and Geometric calibration to review the
maze of engineering and sensor design terminology in hopes of
developing a list of terms, definitions, and best practices for
measuring calibration parameters.
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