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- 8 - 
"High-Stage" Aerial Photography and ERTS Data-Based Systems 
High-Stage Aerial Photography : Because of the need this year (197*0 to 
survey the resources of the much larger (1,500,000 hectares) Custer-CoaIwood 
Area adjoining the Decker-Birney — the possibility of using smaller scale, 
but higher quality, color infrared coverage was taken under consideration. 
There was some precedent for this in Montana in view of some small-camera, 
small-scale tests performed previously in the overall BLM/Minnesota College 
of Forestry project. Also, coverage of this type with 23 x 23cm format 
mapping cameras in other states by a highly experienced commercial aerial 
photography firm using special high-altitude aircraft and a sophisticated 
IMC camera mount appeared to be the logical direction in which to move. 
Again, as on the Decker-Birney, final parameters of the aerial photo 
graphy and ultimately the actual resource survey, were dictated to some ex 
tent by budgetary constraints — i.e., it was highly questionable whether 
the limited funds available for the project would be adequate to cover the 
costs of 1:40,000 aerial photography, as well as the interpretation and 
mapping. As it finally turned out, the operating budget was barely adequate 
to cover the small scale 1:30,000 CIR peak-of-green coverage obtained -- and 
the related interpretation, field checking and mapping, which are currently 
underway. The photography was flown in such a manner as to be "quad-centered 1 
-- that is, each line of photography was flown on the north-south center axis 
of each 7i~minute quadrangle in the area — which coincided with the quad 
rangles used by the U.S. Geological Survey as a base for their 1:24,000 topo 
graphic sheets. In contrast to the Decker-Birney Project, interpretation, 
field checking and mapping were let on contract to a suitably qualified firm 
in lieu of performing all of these tasks within the BLM. 
ERTS Data Applications : As the ultimate in "High-Stage" application, 
considerable attention has been given in the last two years to the possible 
incorporation of ERTS data into first-level extensive resource data surveys 
on extremely large portions of Montana and the Northern Great Plains in gen 
eral. Again, within the limits of what was assumed could reasonably be ex 
pected in the way of operational budgets in a practical sense, attempts were 
(are) being made to explore for possible ERTS data applications. 
A preliminary study conducted north of the Missouri River in the BLM's 
Malta District was reported on by Meyer and Gerbig (1974). In no case was any 
thing more sophisticated used in the study than 70mm bulk ERTS imagery sub 
jected to enhancement and study via the Minnesota College of Forestry's color 
combiner, density level-slicer and (simple) projection-mapping systems. On 
the basis of what was learned on the Malta District study area, actual tests 
of the applicability of similar types of ERTS data to the already-surveyed 
Decker-Birney Area have been accomplished. These results (techniques, classi 
fications) are now being applied to a portion of the Custer-CoaIwood Area with 
the idea of providing an unbiased look at the relative usefulness of these 
kinds of ERTS data as a first-level resource data base for large land surfaces 
in the Northern Great Plains. 
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