326 
R. H. Morris: Photo 
geologic Training in the 
U.S. Geological Survey. 
(Publ. VIIMl) 
tation, owing to the patterns of color sequences, color differences, and distinctive 
color on the photographs, which could be translated into reliable stratigraphic 
and structural information. The aerial color photographs were particularly useful 
in directing field investigations to the location, probable nature, and best method 
of study of a geologic problem. 
Observations were made of the effect that time of day, atmospheric haze, and 
sun angles have on color vision and image sharpness at different viewing dis 
tances and altitudes within the test area. These environmental factors cause 
differences in apparent ground color and strongly affect image sharpness. The 
most significant factors are original ground color as viewed close-up, atmospheric 
haze, and viewing distance. 
Atmospheric haze is usually present over the lowland parts of the test area 
but is not appreciable over the mountainous and upland parts. Where haze was 
not appreciable, visual observations (and 35 millimeter color transparencies) 
showed that reliable color differences between subjects in direct mid-day sunlight 
could be detected over a ground viewing distance of 11 miles. 
Color film is more sensitive to certain colors, such as yellow, than to other 
colors. In one flight strip of aerial color photography both overexposure and 
underexposure were apparent although a constant exposure setting was used and 
the photographs were taken during a 10-minute time interval. The overexposed 
photographs are of areas where yellow ground color predominates. 
Etal de la photographie aérienne en couleur dans les études géologiques du 
bureau géologique des Etats-Unis (U. S. Geological Survey) 
Ce rapport qui traite de l’état de la photographie aérienne en couleur dans les études géologiques 
du Bureau Géologique des Etats-Unis (U. S. Geological Survey) est basé sur les observations 
faites sur le terrain à Death Valley, Californie, une des treize régions survolées en 1955 pour 
l’épreuve de la couleur. Les photographies utilisées sont des photographies verticales à l’échelle de 
1:10 000 avec un format de 9-pouces-carrés et un recouvrement stéréoscopique ordinaire. 
Dans la région de l’épreuve les photographies en couleur ont augmenté l’importance et la sûreté 
des interprétations photogéologiques, considérant que les exemples de successions de couleurs, les 
différences de couleurs et les couleurs distinctives pouvaient être interprétées en informations 
stratigraphiques et structurales. 
Des observations furent faites sur l’effet que le temps du jour, la brume atmosphérique, et les 
angles du soleil ont sur la vision des couleurs et l’acuité des images à des distances et altitudes 
différentes dans la région sous essai. Ces facteurs du milieu causent des différences de la couleur 
apparente de. la terre et attaquent vigoureusement l’acuité des images. Les facteurs les plus signi 
ficatifs sont la couleur primordiale de la terre vue de près, la brume atmosphérique, et la distance 
de vue. 
The following paper, by Mr. R. H. Morris, of U.S.A., was read by title only, 
Photogeologic Training in the U.S. Geological Survey: 
With the increased use of aerial photographs in geological investigations, geo 
logists must be trained in the proper use of aerial photographs and photogram- 
metric equipment. To meet these needs the U. S. Geological Survey has insti 
tuted two training courses: 1) Photogeologic training for geologists, and 2) Pho 
togrammetric training for geologists. 
The photogeologic training program is designed to train the geologist in the 
proper use of aerial photographs and the various photogrammetric instruments 
used in photogeologic study. Training offices have been established at Denver, 
Colorado, and Menlo Park, California. The photogeologic training program is 
conducted throughout the year, and present facilities permit the training of 
about 200 geologists annually. Practical geologic problems involving the use of 
the various photogrammetric instruments are given. Geologists are instructed 
in the procedures of geologic map compilation from aerial photographs. Current 
photogeologic studies as well as investigations already completed by the Photo