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).