————ÁÁÁÁ rali eU E M Ue SPESE UTER =
= = T Jo EE o be DUE Redi os CS oed
ESP SON
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(664)
(3) Burton S. Grant, Chief Engineer of Water Works, Department of Water
Power, City of Los Angeles, California 1952
(4) Corps of Engineers, U.S. Army, Office of the Division Engineers,
South Pacific Division, San Francisco, California, 1952
(5) Division of Water Resources, State of California, Dept. of Public Works,
Sacremento, California, 1952
(6) Water Right Branch, Dept. of Lands and Forests, Victoria, B.C. 1952
INTERPRETATION OF AERIAL PHOTOGRAPHS FOR RANGE
AND AGRICULTURAL INVENTORIES
T. Lommasson and C. E. Waldo.
Aerial photographs provide the most rapid and efficient known means for
mapping the extent and general character of grazing resources and agricultural
crops. Accuracy of detail in range inventory has been about doubled, and costs
have been reduced about half compared to costs by ground methods.
Range inventories determine the extent, distribution and differences in the
vegetative production of the soil, its value for forage, the condition of the forage
crop and its most productive use. Agricultural inventories determine distribu-
tion and kinds of crops and cultivation practices.
Properly to qualify men to successfully conduct these activities, specialized
training is essential, both in field and office operations. Technical men, trained
in the kind of work involved, are the most competent. The order of training
preferably is office technique first, followed by correlation with ground exami-
nation, using the pictures as a guide. The latter verifies or makes subject to
change the determinations made in the office.
For range inventories, location of the major ridges and the drainage pattern
are first mapped on the photographs. Surveyed section lines are then added,
followed by the outlines of the various types of vegetation according to stan-
dards set for each. These are then transferred to the map, usually with the
K.E.K. plotter.
The map is then taken to the field with the photographs and, coincident
with the collection of further data necessary for completion of the inventory,
such changes as are found to be necessary and which could not be distinguished
on the photographs, are made. More work can be accomplished during the short
field season by this method. It reduces stereo examination of photos on the
ground to a minimum. The alternate method is to map directly on the photo-
graphs in the field, and then compile the data in the office. This method slows
field work and lessens accomplishment during the field season.
In range inventories the relationship of topography, accessibility, location
of feed areas, waste and ranch land is more clearly discernable with photographs
than by ground methods. Boundaries of the various areas having different kinds
of cover are much more exact than can be secured by ordinary grounds methods.
Native ranges are almost invariably mixtures of species which are not distin-
guishable from the air. Detail of kinds of grasses and forbs can be only general-
ized from photographs. The various kinds of trees and browse can be deter-
mined more definitely. Pertinent detail must be secured by ground examination.
Agricultural inventories afford greater accuracy of crop variety detail from
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