the panchromatic photo image indicate the 
amount of visible radiation which is reflected 
from features on the ground. Dark tones on 
the positive print indicate objects having low 
reflectance, while light tones indicate those of 
high reflectance. 
The Aerographic Infrared film emulsion (fi- 
gure 5) when exposed with a Wratten 89B 
filter records only near infrared wavelengths 
of light (0.7 to 0.9 micron), i.e., wavelengths 
of radiation just beyond what the human eye 
can see. Since healthy vegetation exhibits high 
infrared reflectance, it appears light in tone. 
Soil generally has relatively low infrared re- 
flectance and appears dark in tone (see figure 
5). The tone contrast between healthy vegeta- 
tion and soil in the near infrared portion of the 
spectrum is particularly significant since range 
managers are concerned about the presence 
and amount of range vegetation. 
Aerial Ektachrome film is a three-layered 
emulsion sensitive to blue, green, and red wav- 
eleneths of light (see figure 2). When they 
are processed, the activated dyes combine to 
form colors which may closely match those of 
the original scene. True color rendition is diffi- 
cult to obtain, and it is especially difficult to re- 
plicate from one photo mission to another due 
to variations in processing, exposure, and spec- 
tral reflectances of the objects as well as the 
sensitivity of the emulsion base. Despite these 
problems, considerable refinement in mapping 
and interpretation can be expected compared to 
black-and-white photographs. 
Ektachrome Infrared Aero film is a three- 
layered emulsion sensitive to green, red, and 
near infrared wavelengths of light which acti- 
vate yellow, magenta, and cyan dyes, respec- 
tively. When processed to a positive image, the 
resulting colors in the photograph are blue, 
green and red, respectively (Fritz, 1967). A 
Wratten 12 or 15 filter is generally used when 
exposing this film to omit blue wavelengths of 
light, to which all three layers of this film are 
also sensitive. On color infrared photographs, 
healthy vegetation—which has relatively low 
reflectance in the visible portion of the spec- 
trum (except in the green region) and rela- 
tively high reflectance in the near infrared— 
appears reddish; hence, healthy vegetation is 
readily detected (see figure 2). Color infrared 
film can be used to record many plant condi- 
tions because the intensity of near infrared ra- 
diation reflected from healthy vegetation is a 
function of the quantity and compactness of 
green foliage, the moisture content of the 
leaves (Weber et al. 1967), the phenological de- 
velopment of foliage, the disease status of the 
foliage (Colwell 1956), and plant cell anatomy. 
Bare soil, which normally appears reddish or 
brownish, appears greenish on this film. 
170 
Detailed photo interpretation of both annual 
and perennial rangeland on 9- by 9-inch film 
format, at scales between 1/8,500 and 1/85,000, 
indicate that panchromatic photos are ade- 
quate for delineating broad vegetation and soil 
boundaries. The level of detail in mapping de- 
pends upon photo quality; the scale of the pho- 
tos; and the interpreter’s skill in discriminat- 
ing tone, texture, shape, size, etc., of significant 
features. 
Aerographic infrared photos conspicuously 
show meadows and other dense vegetation 
types. A variety of moisture regimes, e.g., 
streams, ponds, and standing water, are also 
easily detected; however, such photos are not 
considered useful for general vegetation-soil 
mapping in rangeland. 
Color photographs (both Ektachrome and 
Ektachrome Infrared) permit considerable re- 
finement in mapping accuracy. We would ex- 
pect this gain because the human eye can dis- 
criminate far more shades of color than shades 
of gray. Aerial Ektachrome photographs are 
particularly useful for soil boundary delinea- 
tion where range vegetation is sparse or when 
obvious changes in vegetation type correspond 
to changes in soil type. By using soil color 
characteristics to identify soil types, other re- 
lated information, such as soil fertility and as- 
sociated vegetation, can be inferred. Whereas 
meadow vegetation usually can be identified on 
the color photos, other important range vegeta- 
tion types with sparser foliage cover are not as 
readily discriminated, due to a lack of sharp 
color contrast between vegetation and _ soil. 
This problem becomes more noticeable on 
smaller scale color photography. 
Ektachrome Infrared Aero photos appear to 
be the most easily interpreted for detection, 
identification, and evaluation or mapping of 
vegetation-soil boundaries, changes in vegeta- 
tion density, and moisture regimes, e.g., wet 
meadows sustained by subsurface and surface 
spring water flow, and marshy conditions 
formed by standing spring water (figure 2). 
Likewise, detection and identification of man- 
agement problems are also facilitated by the 
unique color renditions and increased contrasts 
produced on the color infrared film. However, 
many ranges, particularly xeric ranges, may 
not contain a variety of conditions which are 
best discriminated on Ektachrome Infrared 
Aero film. Hence, another film type, e.g., pan- 
chromatic, may be just as useful for inventory 
purposes. 
Before indiscriminately procuring photos for 
inventory purposes, one should consider these 
factors: (a) The diversity of physical and bio- 
logical characteristics (complex vegetation- 
soil-moisture regimes are more interpretable 
