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geology Section of the U. S. Geological Survey are discussed to demonstrate the
practical applications of photogeologic techniques.
Training in photogrammetry is designed to give the geologist a broad know
ledge in the field of photogrammetry. This is important as photogrammetric
instruments are used extensively in photogeologic studies. The course is given
periodically in the offices of the U. S. Geological Survey at Washington, D. C.
and Denver, Colorado.
Education photogéologique au bureau géologique des Etats-Unis
(U. S. Geological Survey)
Avec l’emploi croissant des photographies aériennes dans la cartographie géologique, il faut que
les géologues soient instruits dans l’emploi correct des photographies aériennes et des instruments
photogrammétriques. Dans ce but le Bureau Géologique des Etats-Unis (U. S. Geological Survey)
a établi deux programmes d’éducation. Un cours de photogrammétrie est donné périodiquement à
Washington, D. C., et à Denver, Colorado. Un autre cours des procédés photogéologiques est
donné pendant toute l’année dans les bureaux du »Bureau Géologique des Etats-Unis» à Denver,
Colorado, et à Menlo Park, Californie. Le programme de l'éducation photogéologique fournit aux
géologues une connaissance active des procédés photogéologiques ainsi que des instruments photo
grammétriques. Les études photogéologiques complétées jusqu’à présent sont discutées pour
démontrer les applications pratiques de la technique.
Mr. F. C. Robertson, of England, presented his communication, on Soil anti
Vegetation surveys in the Middle East. No summary exists.
A paper by Mr. G. Heath, of U.S.A., was read by Mr. J. Cain, of U.S.A.
A Comparison of two Basic Theories of Land Classification and their
Adaptability to Regional Photo Interpretation Key Techniques:
In the study of regions it is important to be able to divide them into
homogeneous units so that their environmental associations may be analyzed.
Man has been describing and classifying land for centuries, but only recently
have scientific methods been developed. Davis was the founder of a school of
physiographical description which was widely accepted. Two of his disciples
took his principles and digressed in different directions. Bowman divided the
United States into physiographic provinces and Fenneman later revised them
and subdivided them further. Bowman then became a student of human geo
graphy and paid less and less attention to physiography, placing his emphasis
on the correlations between topographic types and man’s activities. Sauer had
parallel views and helped develop a similar system of land type classification for
the Michigan Economic Land Survey. This survey became the basis for land
classification surveys in the United States for the last 35 years. Land or terrain
types have been widely used in military intelligence surveys. The physiographic
method of land classification has been chiefly used for geographic description,
but has also been used in intelligence studies. The two methods of land classi
fication are illustrated by use of two regional keys. Fenneman’s methods have
been adapted to key techniques, and in the illustration used the Navajo Section
of the Colorado Plateau was keyed out. The methods of Bowman and the
Michigan Economic Land Survey have been adapted to photo interpretation and
were used to key out the basin type of the Colorado Plateau. The Colorado
Plateau was selected because the author knows it well and because the environ
mental contrasts between terrain types reach great extremes there. The advan
tages and disadvantages of the two methods may be summarized as follows:
Physiographic subdivision permits complete descriptions, allowing for climatic
and economic differences within a region. However, subdivisions depend upon a
map for photo interpretation, which introduces errors. Physiographic subdivisions
are not homogeneous and their descriptions cannot be used to analyze any
particular site. An essay format is necessary, which makes a weak key, and being
purely descriptive the key soon becomes obsolete. Terrain types are easy to
V. C. Robertson: Soil
and Vegetation surveys
in the Middle East.
G. Heath: A Comparison
of two Basic Theories of
Land Classification and
their Adaptability to
Regional Photo Inter
pretation Key Techniques.
(Publ. VII H 2 in General
Report VII)