HAND-HELD RADIOMETER STUDIES OF VEGETATION
IN SITU: A NEW AND PROMISING APPROACH
Compton J. Tucker
Earth Resources Branch, Code 923
NASA/Goddard Space Flight Center
Greenbelt, Maryland 20771 USA
Abstract
The development of hand-held radiometers for in situ remote sensing data
collection is traced from detailed field spectrometer work through to hand-
held radiometers. Several 2xamples of this new approach of spectral data
collection are reviewed for studying vegetation.
Introduction
There currently is a need for rapid, convenient, and accurate in situ
ground-based remote sensing data collection instruments for measuring
vegetation. This data is needed principally to increase our understanding
of the information available in the spectral reflectance-vegetation inter-
action. A greater understanding of this coupling between spectral reflectance
and vegetation will lead to two objectives: (1) a greater understanding of
satellite and aircraft remote sensing imagery of terrestrial vegetation; and
(2) the use of these techniques for nondestructive ground-based studies of
vegetation by themselves. Regardless of the altitude of the sensor (s) in
question (2 m, 2000 m, or 700 km) the same information is potentially
available.
Our understanding of vegetational remote sensing will be increased via
controlled in situ experimentation. The easiest and most controlled way
to do this is with some ground-based method. It has proven to be extremely
difficult to accurately and precisely reconstruct the status of vegetation
in Landsat pixels, for example. In this situation, one must deal not only
with atmospheric effects, sun angle effects, etc., but with the difficulty
of sampling enough pixels on the ground to represent a valid and controlled
sample (each pixel = ~ 0.45 ha).