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As Mr. G. D. Whitmore, U.S.A., was not present at the Congress, his paper 
»Economic Factors in the Integrated Photogrammetric System of the U.S. 
Geological Survey», was read by Mr. Davidson. Summary: 
The Geological Survey is currently making changes in equipment and pro 
cedures that affect all the major aspects of its topographic mapping operations. 
A principal source of economy is the use of convergent low-oblique photo 
graphy in conjunction with Twinplex instruments for aerotriangulation and ER- 
55 plotters for compilation. This combination affords a high C-factor and large 
model area, resulting in operating economies in aerotriangulation, stereocompi 
lation, and supplemental-control surveys. The Twinplex 3-model bridge offers a 
practical means of extending vertical (as well as horizontal) control accurately, 
whereas conventional methods require at least 6 models to bridge the same area 
with results that are generally not acceptable for vertical-control extension. Be 
cause of the increased model size, there are fewer models to set up in the ER-55 
plotter for compilation and less time required for joining detail from model to 
model. The cost of supplemental control is decreased because of the practicability 
of vertical-control extension, and the reduction in the number of models, with a 
consequent reduction in the number of control points required. The capital 
outlay for the new Twinplex and ER-55 equipment is relatively modest. 
The Stereotemplet system for horizontal aerotriangulation achieves economies 
on some types of projects by permitting greater flexibility in the placement of 
horizontal-control points obtained in the field. 
The use of a variable-ratio pantograph with the stereocompilation instrument 
speeds up the compilation procedure by permitting the manuscript map to be 
drawn at or near the publication scale. 
The use of scribing techniques permits great flexibility of operations in pro 
ducing the map manuscript, in cartographic finishing, and in reproduction. 
Among the advantages of this technique are: production of smooth, uniform 
copy, using simple tools to replace expensive pen-and-ink drafting; ease of repro 
duction; convenience of field completion; quick transfer of edges from one sheet 
to another; elimination of costly and time-consuming photographic steps; simpli 
fication of revision and correction processes; and preservation of the original 
contour compilation as reproduction copy, under favorable circumstances. 
The integrated system is already saving money in the principal phases of 
mapmaking. As the system gains momentum, an increasing degree of economy is 
expected. 
Facteurs économiques du système intégré de photogrammétrie du 
U.S. Geological Survey 
Actuellement, le Geological Survey effectue des changements des appareils et méthodes qui 
affectent tous les aspects principaux de ses opérations cartographiques. 
Une source principale d’épargne est l’usage de la photographie convergente bas-oblique de concert 
avec l’appareil Twinplex pour l’aérotriangulation, et l’appareil ER-55 pour la compilation. Cette 
combinaison permet un grand C-facteur et une grande surface du modèle; cela donne des épargnes 
en l’aérotriangulation, la stéréocompilation, et les levés de contrôle supplémentaire. La première 
mise de fonds pour obtenir les appareils nouveaux Twinplex et ER-55 est relativement modérée. 
Une autre source principale d’épargne est l’usage des techniques de »scribing» pour remplacer 
le dessin à la plume dans la production de la carte manuscrite, le finissage cartographique, et la 
reproduction. Les techniques »scribing» permettent beaucoup de flexibilité et se prêtent à des 
procédés qui épargnent du temps et de l’argent. 
Des procédés connexes qui contribuent à l’économie du système sont l’usage du pantographe à 
ratio variable pour permettre la compilation à échelle réduite, et l’usage des »Stereotemplets» par 
méthode alternative pour l’extension du contrôle horizontal. 
Dr. A. M. Wassef, Egypt, presented his communication to the Congress, 
»Applications of Statistics in Survey Work». Summary: 
In a paper delivered at the Washington Meeting of ISP the writer submitted a 
critical discussion of some outstanding works in photogrammetry to prove that 
G. D. Whitmore: 
Economic Factors in the 
Integrated Photogram 
metric System of the 
U.S. Geological Survey. 
(Publ. IV W 1) 
A. M. Wassef: 
Applications of Statistics 
in Survey Work.