COMMISSION II 
Président: Professeur Dr. W. K. Bachmann, Suisse 
Secrétaire: Ingénieur W. Haberlin 
Procès-verbal de la séance du 18 juillet 1956, 
à 10.00 heures (a) 
Le président ouvre la séance et donne un exposé sur l’activité de la Commis 
sion II depuis le Congrès International de Photogrammétrie à Washington 1952. 
Il donne aussi les traits principaux du rapport général de la commission et de 
l’essai no 2 Vercors. 
The Chairman opened the meeting and gave an account of the activities of Commission II since 
the Washington Congress. He also mentioned the main features of the General Report of the 
Commission and of Test No. 2, Vercors. 
Ensuite la parole est donnée à M. W. C. Cude, Etats-Unis, pour la présentation 
de sa communication »Experiences with convergent photography». Résumé: 
The paper discusses investigations with convergent photography using wide 
angle lenses following the same trend of reasoning which had prompted the 
convergent photography investigations in Europe prior to the development of 
the wide angle lens. Inadequate map coverage in the United States requiring 
expeditious action and economy of personnel and equipment made the use of 
convergent wide angle photography seem worthwhile, since higher flight alti 
tudes would be possible and commonly used U. S. equipment would require 
little modification. 
The first laboratory tests with multiplex equipment indicated an increase of 
1.5 to 2.0 times the contour accuracy of vertical photography taken at the same 
altitude. No increase in planimetric accuracy was noted. 
The Kelsh plotter was then given the same type of test with both vertical 
and convergent photography with approximately the same results, except that 
the stereomodels of the convergent photography suffered a greater loss in 
resolution. This was probably due to the greater magnification of the Kelsh 
plotter and the unusual depth of focus of the multiplex. Special plate holders 
designed for the purpose did improve the resolution, however the contouring 
accuracy remained the same. 
Aerial triangulation requirements involving the bridge from one convergent 
stereomodel to the next convergent stereomodel led to the development of the 
Twinplex by the U. S. Geological Survey and the Stereopontometer by the Corps 
of Engineers to suit their specific problems. 
Tests were also conducted on the Zeiss Stereoplanigraph C-8 and the Wild 
Autograph A-7 with promising results. 
To properly study the magnitude of instrumental errors and for calibration 
purposes special glass grid plates were made. Tests with these showed possi 
bilities of even higher contour accuracies. 
Work continues on block adjustment of a series of convergent flights with 
variations of control and procedures. 
IF. C. Cude: Experiences 
with convergent 
photography. 
(Publ. II C 1) 
163