on color and false color photos); (b) The level 
of information desired (color photos provide 
considerable refinement in mapping, and 
large-scale photos show greater ground de- 
tail), and (c) The cost differential between 
black-and-white and color photos (color photos 
are generally two to three times greater in cost 
per exposure). Final consideration should also 
be given to the tradeoff between choice of film 
type, cost per exposure, and scale of photogra- 
phy. 
As an example, in some range environments 
the increased information derived from inter- 
pretation of color infrared photos (compared 
to panchromatic) may permit procurement of 
smaller scale photography (e.g., 1/380,000) 
which covers a larger range area. Thus, the 
fewer color exposures required may offset the 
additional cost per exposure and bring the 
total inventory cost in line with the cost of 
procuring black-and-white photos taken at a 
relatively larger scale (1/15,000 to 1/20,000). 
Line Scan Devices 
The use and interpretation of line scan im- 
agery from an optical mechanical scanner is 
still in experimental stages. Figure 6 shows 5 
of 18 spectral bands which record both reflected 
and emitted radiation in the ultraviolet, visible, 
near infrared, and thermal infrared portions 
of the electromagnetic spectrum. By comparing 
the tone signatures of the various range fea- 
tures illustrated, one can see that the energy 
responses from bands of the spectrum are very 
different. Some range features are emphasized 
on one band but are obscured on another band. 
Consequently, it is most desirable to interpret 
the band(s) which reveal the greatest infor- 
mation about the features of particular inter- 
est. For example, an image obtained in the visi- 
ble band of the spectrum is better for delineat- 
ing the most vegetation and soil boundaries, 
whereas significant moisture regimes are em- 
phasized on the thermal infrared image. 
Advantages of the optical mechanical scan- 
ner over photographic systems previously dis- 
cussed are: (1) Imagery can be generated 
simultaneously in wavelengths both within and 
outside the photographic region; (2) the signal 
is in an electronic form and can be stored on 
magnetic tape or converted to a_ photolike 
image; and (3) the detectors generally have a 
wide dynamic range and hence more tone 
values can be discerned. On the other hand, 
limitations of the scanner are: (1) It is more 
complex than a camera; (2) it generally has 
poorer spatial resolution than a camera; and 
(5) it has distortions which are difficult to 
eliminate or rectify (Lowe 1968). 
Thermal infrared imagery of perennial 
rangelands in northeastern California, has been 
obtained with a Reconofax IV infrared imager 
(see figure 7). Dark tones within the image in- 
dicate low emitted radiance associated with 
low temperatures, whereas light tones indicate 
high emitted radiance associated with features 
which are warm. This day-or-night sensing de- 
vice provides a capability for discriminating 
objects having different thermal emission 
(temperature emissivity). Applications sug- 
gested by the thermal infrared image in figure 
7 include detection of springs and differentia- 
tion of water temperatures. Other applications 
of thermal infrared imagery which seem feasi- 
ble are: (a) Monitoring moisture regimes be- 
fore, during, and after the grazing season; (b) 
determining range readiness and availability 
of stock water for efficient range management; 
(c) detecting moisture regimes which aid in 
analyzing the presence or distribution of im- 
portant vegetation types; and (d) inventory- 
ing of domestic or wild animals. Resolution 
constraints presently limit operation of  in- 
frared imagers to relatively low altitudes, but 
even so, the feasibility for detecting animals in 
the open, i.e., not beneath a vegetation cover, 
has been demonstrated (Garvin et al. 1964; 
Carneggie et al. 1966, 1967). 
Side-looking radar devices have been oper- 
ated over rangeland in Oregon, California, 
Utah, and Kansas. Analysis of radar imagery 
for vegetation studies is summarized by Moore 
and Simonett (1967). Their results indicate 
that radar may have a role in preparation of 
small-scale regional or reconnaissance vegeta- 
tion maps, particularly where there are pron- 
ounced structural differences between plant 
communities. Although the resolution of radar 
imagery is generally much lower than that of 
photographs taken at the same altitude, the 
ability of radar devices to obtain imagery day 
or night, and during most adverse weather 
conditions, makes it a promising sensor for a 
special-purpose inventory—for example, in 
range environments characterized by persis- 
tent cloud cover which would prevent the at- 
tainment of photographs. There is also evi- 
dence that longer wavelength radar pulses, ca- 
pable of penetrating soil to various depths, 
may be extremely useful for analysis of soil 
properties. 
REMOTE SENSING DATA ANALYSIS 
Analysis of most remote sensing data de- 
pends primarily upon recognition of the energy 
responses (associated with reflectance or emitt- 
ance of radiation) from objects in the various 
portions of the electromagnetic spectrum. 
Through procurement and analysis of many 
kinds of remote sensing imagery, such as have 
been presented in this paper, an image analyst 
soon becomes familiar with tone or color re- 
171 
