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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)