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Mesures physiques et signatures en télédétection

E.J. Milton, E.M. Rollin and A.More
NERC Equipment Pool for Field Spectroscopy
Department of Geography
University of Southampton
Southampton S09 5NH, U.K.
The paper describes two hypertext-based training applications developed by the UK Natural Environment
Research Council Equipment Pool for Field Spectroscopy (NERC-EPFS). The first introduces NERC-EPFS and
explains its role in loaning field spectroradiometers and associated equipment to UK research groups, and the
training and research activities of the Pool. The second application is a systematic review of the accuracy of
field spectroscopy and comprises five main sections: Primary standards, Instrument characteristics. Panel
characteristics, Environmental factors and Measurement methodology . The written paper illustrates the type of
material contained in the computer-based products by summarising three of the many experiments included.
The first shows how changes in temperature have a strong influence upon the radiometric sensitivity of a
Spectron SE590 spectroradiometer, particularly above 700nm.The second shows how in the field situation in
temperate latitudes skylight moderates the non-lambertian properties of a Spectralon panel. The third
experiment investigates the relative accuracy of measurements made with the sensor hand-held or held in a
fixed support. No significant difference in nadir reflectance was measured from grass and asphalt surfaces
using a Spectron SE590 spectroradiometer operated in the two modes.
KEY WORDS: field spectroscopy, training, methodology, hypertext, errors
In January 1988 the UK Natural Environment Research Council established an Equipment Pool for Field
Spectroscopy (EPFS) located at the University of Southampton and this now comprises five inter-calibrated
field spectroradiometers and associated instruments. The EPFS is staffed by a Pool Manager and a Research
Assistant, and its main function is to provide field spectroradiometers to the UK research community, and to
train prospective users in field spectroscopy. An important subsidiary role of the EPFS is to perform
fundamental research on the methodology of field spectroscopy.
Although much of the training undertaken by EPFS is 'hands-on' we have also identified a
need for interactive computer-based training materials which can be distributed more widely, and have
developed two hypertext applications using a program called Toolbook from Asymetrix Inc.
This application is intended as an introduction to the NERC Equipment Pool and its activities and comprises a
series of modules linked through a contents page which is shown in figure 1. Introductory sections describe the
function of EPFS and the various instruments available for loan, and nested modules within these sections
allow the user to access more detailed information on the subject of field spectroscopy and a comprehensive
bibliography. Other main sections cover the calibration of EPFS instruments and the system by which their
calibration is traceable to the UK National Physical Laboratory. Considerable attention is also devoted to the
different methods by which spectral reflectance may be measured in the field, and advice given on the practical
aspects of field measurements. Finally, sections cover the procedure by which prospective users may apply for
use of the instruments, and examples of completed studies are provided, together with a full set of information
notes and technical data produced by EPFS staff.