32 HISTORY OF PHOTOGRAMMETRY IN THE UNITED STATES
later to be one of the most practical and
potent American stereoscopic plotting
machines, was conceived and partially
developed by Harry T. Kelsh and others
while employed by the Soil Conservation
Service.
Besides making use of photographic
coverage for making maps and mosaics,
the Service further developed photo-
grammetry for its planning and erosion
surveys, land use, determination of slope,
flood control surveys, watersheds, timber
cultivation, range surveys, irrigation, po-
tential land uses, farm surveys, vegetation
classification, reservoir capacity surveys,
and sedimentation studies.:?/ 9:10
PHOTOGRAMMETRIC INSTRUMENTS DEVELOPED
Vari-Scale templet punch and slotter.
The Cook Stereoscopic Plotter.
Magruder slotter and center punch (Figure 1).
Initial research and early development of Kelsh
Plotter. (This plotter was subsequently com-
pleted by U. S. Geological Survey and is now
produced commercially. See U. S. Geological
Survey Report.
PATENTS
Slotted templet method—C. W Collier
Vari-scale slotter and center punch—E. W. Ma-
gruder and H. T. Kelsh
REFERENCES
1. Woodward, L. A., “Mosaic and Plani-
metric Mapping,’ PHOTOGRAMMETRIC EN-
GINEERING, Vol. V, No. 4, 1939.
2. Kelsh, H. T., “Report of Tests of the
Slotted Templet System of Radial Triangu-
lation,” PHOTOGRAMMETRIC ENGINEERING,
Vol. V, No. 4, 1939.
3. Cude, William C., “Planimetric Mapping in
the Soil Conservation Service," PHoro-
GRAMMETRIC ENGINEERING, Vol. VI, No. 3,
1940.
4. Kelsh, H. T., *Hunting Rubber from the
Air,” PHOTOGRAMMETRIC ENGINEERING,
Vol. IX, No. 4, 1943.
5. Woodward, L. A., “Aerial Photography as
a Map Substitute,” PHOTOGRAMMETRIC
ENGINEERING, Vol. X, No. 2, 1944.
6. Schlatter, E. S., “Map Accuracy,” PHOTO-
GRAMMETRIC ENGINEERING, Vol. X, No. 3,
1944.
7. Kelsh, H. T., "Germany's Use of the
Slotted Templet System,” PHOTOGRAM-
METRIC ENGINEERING, Vol. XII, No 3,
1946.
8. Schlatter, E. J., “The Variable Elevation
Wedge," PHOTOGRAMMETRIC ENGINEERING,
Vol. XII, No. 3, 1946.
9. Magruder, E. W., “Aerial Photographs and
the Soil Conservation Service,” PHOTO-
GRAMMETRIC ENGINEERING, Vol. XV, No.
4, 1949.
10. Kelsh, H. T., "The Slotted Templet
Method,” U. S. Dept. of Agriculture Pub.
404.
So1L, SURVEY, DEPARTMENT OF AGRICULTURE
Interest in the possible use of aerial
photographs for mapping soils first came
about in the early 1920's when some ex-
perimental work was done. Photographs
were first used in the soil surveys of a county
in 1929 when they were obtained for
Jennings County, Indiana through the
efforts of T. W. Bushnell of Purdue Uni-
versity and Mark Baldwin of the Division
of Soil Survey, U. S. Dept. of Agriculture.
These photographs were used to prepare
soil maps. Although the advantage of
photography in soil mapping became ap-
parent they did not come into immediate
general use, chiefly because of their high
cost at the time.
About 1935 aerial photographs were
flown for the Agricultural Adjustment
Administration in a nation-wide program
and resulted in low-cost photography for
most areas where soil surveys could be
made. The use of aerial photographs be-
came one of the major advances in soil
surveys, where the photographs are used
in both the field operations and in the
preparation of maps. Mapping is not
usually undertaken until air-photos are
available.
As useful as photographs are, little can
be interpreted about soils without field
work in soil mapping and careful study on
the ground.
The photos permit rapid and accurate
plotting of soil boundaries, but sound
classification and mapping of soils can be
achieved only by detailed field study of
the soils themselves, supplemented by
laboratory study of samples and examina-
tion of soil profiles.
REFERENCES
Soil Survey Staff. 1951. Soil Survey Manual.
U. S. Dept. of Agriculture Handbook No. 18,
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