73 
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in the study area. 
Patterns evident on both the ERTS imagery and large scale photography were 
similar in all phases of the mapping effort. Evaluation of the small scale 
aerial photography (1:120,000) proved to be of little value since more detailed 
information could be gained on the relatively larger scale photography (1:30,000). 
The use of an ERTS image, aerial photographs (1/30,000) and ground data in 
a multistage analysis proved to be a valuable combination for regional inventory 
of the soil resource. 
Land units most easily interpreted were the units consisting of shallow, 
eroded soils of upland plateaus with Juniper-low sagebrush community, and those 
with deep, uneroded soils of upland basins with dense Rabbitbrush community. 
Interpreters had the most difficulty in distinguishing sandy, dune soils with 
dense Big sagebrush-Bitterbrush vegetation type from the silty, lacustrine 
basin soils with low density Rabbitbrush or Greasewood (Sarcobatus vermiculatus). 
Land units with high surface rock density were easily identified due to the 
homogeneous dark gray tones on the imagery. Occasionally, however, this rock 
cover transgresses adjacent land units making it difficult for interpreters to 
map the unit boundary accurately. 
When mapping on a regional level, soils must be evaluated and examined 
with a certain degree of bias because they vary within and between vegetation- 
terrain types. Previously, the only certain way to detect and document this 
variability was through highly detailed survey procedures. When surveying 
on a regional level, however, detailed examination based on conventional 
techniques succeeds in only expending valuable time, money, and personnel. What 
is desired for reconnaissance level mapping is the grouping of soils which will 
behave similarly under certain management programs. In the past these groupings 
have been made from completed, detailed surveys by combining smaller mapped 
units of similar types of soils into larger units, associations. The procedures 
discussed in this paper which are based on mapping land system units and 
documenting the major characteristics of that land unit, eliminate the need for a 
detailed survey before one can group similar types of soils. Satellite imagery 
though low in resolution proved to be of sufficient resolution for grouping 
similar soils, vegetation and land types by distinguishing large units and 
coalescing the small inclusions which tend to confuse the interpreter on high 
resolution large scale photography. By utilizing a strong multistage analysis 
approach, ranging from ERTS imagery to aerial photos to strategically located 
field profile plots, soil resource evaluation and mapping is quite feasible on 
a regional level at a considerable savings in time, money, and personnel, with 
no sacrifice of the accuracy needed for resource management objectives at this 
level. 
Ground data collection efforts for the project were hampered by lack 
of accessibility to plot areas and resulted in a portion of the interpreted 
area not being verified on the ground. This portion of the vegetation mapping 
effort was classified through photo interpretation by using the convergence 
of information gained in the previously examined regions of the study area and/ 
or through data sources present prior to the study. Time was the most critical 
constraint during the project. The total time allocated and needed to complete 
the mapping efforts, however, using remote sensing data products reduced the 
time and costs considerably from the conventional methods of rangeland inventory 
without use of photography. The total vegetation mapping effort performed on 
color infrared aerial photos (1/30,000), including interpretation time,