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Affiliate status is granted by the CEOS members in order to
establish links to other satellite co-ordinating groups and to
scientific or governmental bodies that are international in
nature and currently have a significant programmatic activity
that supports CEOS objectives. Currently, the following
organizations hold affiliate status:
e FAO (Food and Agricultural Organization of the United Na-
tions),
e GCOS (Global Climate Observing Program),
e GOOS(Global Oceans Observing Program),
e ICSU (International Council of Scientific Unions),
e IGBP (International Geosphere-Biosphere Program),
e IOC (Intergovernmental Oceanographic Commission),
e UNEP United Nations Educational Program),
e UNOOSA (United Nations Office for Outer Space Activi-
ties?),
e WCRP (World Climate Research Program),
e WMO (World Meteorological Organization).
A previous application of ISPRS for affiliate status was denied
by the CEOS Plenary on the ground that ISPRS is primarily an
international lobby organization rather than a scientific body.
a renewed application for affiliate status requires good prepara-
tion and some lobbying with CEOS members;, however, the
addition of the Terrain Mapping subgroup in the WGCV
should make it significantly easier to argue that ISPRS has "a
significant programmatic activity that supports CEOS objec-
tives". The author believes that an active participation of
ISPRS in CEOS activities, especially terrain mapping, will
be beneficial to future ISPRS activities.
5. INTERNATIONAL STANDARDIZATION IN
COLOUR ORDER SYSTEMS
"Colour" is not an easy subject to deal with as it involves the
combination of two aspects, colour stimulus and colour per-
ception.
Colour stimulus refers to the physical aspects of colour, the
electromagnic radiation with a certain spectral distribution
which can be measured. Colour-stimulus related questions
can be discussed under the heading colour optics, and they
include for example
e radiant energy,
e wavelength and colour,
e monochromatic stimuli,
e fluorescence,
e colour temperature,
e colour mixture (better colour-stimulus synthesis),
e three-colour separation,
e colour printing.
Colour perception refers to psychological aspects of colour,
that is the way in which we perceive colour. The psychologi-
cal aspects of colour are closely related to the physiological
aspects of colour, that is the way in which the human visual
nerve system works.
The combination of the physical and the psychological aspects
of colour leads to a psychophysical way to treat colours which
resulted in a scientific branch called colorimetry.. The Human
visual system is here treated like a black box.
Colour systems gain additional interest as a result of an
increase use of either digital imaging systems or of digitized
images. A few colour systems will now be reviewed briefly.
5.1 CIE System
This CIE colorimetric system is basically a method of ana-
lyzing colour stimuli with respect to their ability to generate
colour percepts. It is based on the ability of the human visual
system to see a monochromatic colour stimulus and a mixture
of three primary colour stimuli as the same colour metamery).
Hence, it is possible to define all visible colours as a mixture
of three primary stimuli. The International Illumination Com-
mission (CIÉ from Commission Internationale de lÉclairage)
has determined the response of standard observers for a 2° and
a 10° visual field, the spectral characteristics of standard light
sources and a system of describing colours known as chroma-
ticity diagram.
Based on the chromaticity co-ordinates, two colour spaces for
the evaluation of small stimulus differences were in 1976 tem-
porarily accepted by CIE after a long dispute and repealed a
few years ago: CIELAB and CIELUV. CIELAB proved to be
more useful in connection with reflective material (Photo-
graphic prints, printed materials), CIELUV for projected im-
ages (television).
5.2 NCS and Munsell Systems
A set of three elementary colours has long been used as base
colours. These colours were later combined in three opponent
pairs (white-black, yellow-blue, red-green) in recognition of
the fact that signals from the trichromatic receptor system in
the retina are processed to polarities. Hence, this psychologi-
cal system is known as Natural Colour System. It has become
under that name a Swedish national standard and has been
considered for introduction as an international standard but
work was discontinued for the time being as the Swedish sy-
stem carries a personal copyright unacceptable to ISO. The
system is physically realized in form of a colour atlas con-
taining a large number of colorimetrically specified samples,
and the colorimetric specifications are tied to a certain CIE
standard illuminant and standard observer
The other major system beside the NCS is the Munsell system
also based on a colour atlas. While the NCS colours fit rea-
sonably equally distributed into a double cone, have the Mun-
sell colours a more irregular distribution leading to a presenta-
tion in a Munsell tree. Also, the three chromatic opponent
pairs are not in exact opposite positions on Munsell's colour
circle.
5.3 Monitor colour systems
Monitors use primary colours determined by available pig-
ments; these have nothing to do with the CIE primary stimuli.
In recognition of the fact that colours can be interactively
better controlled or transmitted with a certain degree of loss-
free data compression, transformations into several monitor
colour spaces have become common:
e HSV (hue, saturation, value),
e HLS (hue, lightness, saturation),
e HVC (hue, value, chroma),
e IHS or HIS (hue, intensity, saturation),
e YIQ (luminance Y, red - Y, blue - Y used in NTSC),
e YCC (Kodak system similar to NTSC)
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B1. Vienna 1996
