- 670 =
Hand-held radiometers, as referred to in this report, are some light-weight
device with various bands configured spectrally by a custom-made interference
filter for each band (see Pearson, et al., 1976).
A logical extension of hand-held devices to more sophisticated 6 to 15 band
instruments could easily be undertaken. This would make available for the
first time the possibility of a standard ground-based remote sensing device
which would be easy to operate, accurate, inexpensive, and could be used as
a 3-band device or as a 6 -15 band truck mounted instrument. Such work is
currently underway at NASA/GSFC.
Conclusions
1. Additional and numerous ground-based remote sensing studies are needed
immediately to expand our understanding of spectral reflectance from
vegetation targets. This will not happen quickly if only field spectro-
meters are used.
2. Discrete band radiometers, configured by custom-made interference
filters, have proven tó overcome the limitations of spectrometers.
Spectrometers are needed, however, to define those wavelength regions
to be used in the discrete band radiometers. A previous effort in
these respects is reviewed and documented.
3. Discrete band radiometers, whether they are hand-held ( £ 6 bands) or
boom supported (8-15 bands) offer a logical means of expanded remote
sensing data collection. They are inexpensive and could be standardized
to facilitate inter-comparisons between different investigators.
4. The value to any life science discipline when instrumentation becomes
available that does not require extensive knowledge of physics or
electronics for operation is great. An example would be the tremendous
biological advances made possible by the electron microscope when
biologists (cytologists, anatomists, physiologists, etc.) could operate
these instruments vis-a-vis the use of them in biological research by
only physicists. Remote sensing instruments are needed for plant
Scientists. In this fashion, the potential of remote sensing of
vegetation will be realized.
Addendum
I have attempted to document the development and applications of discrete
band hand-held radiometers by reviewing the work which led up to this new
approach. As such, I have only reviewed my/our own work. This was not
done for egotistical reasons but simply because that was the course of
events. It should be mentioned that workers at LARS/Purdue have reached
the same conclusion from their more recent efforts in the collection of
field spectrometer data (Robinson et al., 1978). I feel any group who takes
this approach for monitoring vegetation and is successful quickly realizes
the limitations of field spectrometer data collection. Discrete band