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Previous efforts to better understand the spectral reflectance of vegetation 
have used spectrometers in various field configurations. This has proven to 
only partially alleviate the dirth of controlled in situ data from vegetation, 
however. 
Spectrometers are capable of providing detailed spectra from vegetated targets. 
They sacrifice mobility and hence wide area coverage in achieving the capa- 
bility of detailed wavelength measurements. 
Advantages and Disadvantages of Spectrometers 
Spectrometers are basically laboratory devices. They require sophisticated 
electronic support in data collection, reduction, and storage. They are in 
need of frequent recalibration and maintenance. They do, however, offer the 
possibility of collecting detailed reflectance data as a function of wavelength. 
Spectrometers are generally not very mobile as they are usually trailor or 
cherry-picker mounted. This restricts their spatial data collection efforts 
substantially. In addition, they are expensive to buy, expensive to operate, 
and require a highly trained staff to operate and maintain. These factors 
greatly restrict the wide-spread use of field spectrometers in ground-based 
remote sensing studies.  Hand-held radiometers, by contrast, have complementary 
strengths and weaknesses. 
Advantages and Disadvantages of Hand-Held Radiometers 
Hand-held radiometers are the strongest where spectrometers are the weakest 
and vice versa. They can be built as field devices. They are not in need 
of involved electronic, data collection, and/or data reduction support. They 
do not require frequent maintenance or recalibration. They do not offer the 
possibility of collecting detailed wavelength information. 
Hand-held radiometers are as mobile as the operator. They are inexpensive to 
buy, inexpensive to operate, and do not require a highly trained staff to 
operate and maintain. They are well suited for the biologist or agronomist 
with no understanding of electronics. 
The Role of Spectrometers and Hand-Held Radiometers 
Both spectrometers and hand-held radiometers are needed in ground-based studies 
of vegetation.  Spectrometers should be used to collect the detailed spectral 
reflectance data from vegetated targets and hence establish the various 
physiological-spectral reflectance relationship(s). Once this has been done, 
hand-held radiometers should be employed to expand the research dramatically. 
I will now illustrate this by reviewing the spectrometer--hand-held radiometer 
development of L. D. Miller, R. L. Pearson, and C. J. Tucker, who, at that 
time, were at Colorado State University and associated with the U. S. Inter- 
national Biological Program (IBP) Grassland Biome. 
    
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