71 
lapping and 
jximately 
)00 scale U-2 
)f the mapping 
Lstics during 
racteristics 
subsurface 
itative units 
eliminated 
s transferred 
Lanning unit 
The classifi- 
srson (1973) 
i on BLM 
set was the 
^eland 
sites and small 
were utilized 
sitive area 
s on map sheets 
is was utilized 
the study area, 
und data were 
ing land systems 
Is, (b) 
landforms 
s all of recent 
determined by the accessibility of the land unit. Four mapping cells were 
interpreted both on the ERTS imagery and aerial photography. Land unit classi 
fications within the mapping cells were based on image characteristics and 
information gained through field plot examination. The soils within the land 
units were mapped at the soil association level which in turn are governed by 
landscape position. The vegetative communities were classified according to 
species composition and dominance within a given land unit. Landforms were 
stratified into two first order classes on the basis of whether they were of 
a primary (residual) or secondary (alluvial, aeolian, or lacustrine deposits) 
nature. Further stratifications were based on the specific type of landform 
within each of these first order classes. 
RESULTS 
Multidate analysis of ERTS-1 imagery during the spring and summer 
months allowed interpreters to observe the dynamic changes in the rangeland 
resources present in the study area. Analysis of multidate imagery during the 
spring enabled interpreters to determine when forage and water sources were 
available due to their characteristic tones on the imagery. Water quality in 
the deeper reservoirs was shown to increase as the season progressed. 
On the early April ERTS image no available forage could be detected. 
Water bodies and reservoirs contained ample water supply which may have been 
relatively high in suspended material as evidenced by the light gray tones 
on the imagery depicting a sediment load. 
The late spring ERTS show an increase in forage development on upland 
areas subsequent to the snow melt (increase in red tones), while forage associated 
with low lying areas on the plains which was green early in the season has 
subsequently dried (red tones change to light yellow). Water quality has 
increased in the deeper surface water bodies due to the clearing of the water 
bodies as evidenced on the imagery by increasing dark blue or black tones. 
ional level 
from the ERTS-1 
located on the 
ion-terrain 
future intensive 
ately 25,000 
to the area 
scale. Maximum 
11s which 
types in 
formation gained 
a given land 
that unit. If 
were sagebrush 
ority of the 
n was ultimately 
Analysis of multidate ERTS-1 imagery taken in the summer (1972) showed 
a significant decrease in the surface area of water bodies and reservoirs. 
Many small ephemeral reservoirs dissipated during the four successive ERTS 
passes, while ephemeral vegetation began to occupy the moist sites that were 
formerly reservoirs. Change detection techniques enabled interpreters to 
accurately determine the extent and location of areas of decreasing water supply, 
areas of available forage, and areas of decreasing forage supply by changes 
in tonal and textural patterns between dates in the late summer season. 
Single date ERTS imagery is most useful when the synoptic coverage is 
utilized effectively; that is when the study areas are very large (greater 
than 100,000 hectares) and a general overview of the entire study area enables 
broad stratifications of the various resources. The single data of ERTS 
imagery which covered all of the project area (July 26, 1972) was stratified 
into major resource types, land uses, and variations in cover or productivity 
based on differences in tone and textural patterns on the image. Though some