(212) 
I. 55 to 3.10 p.m. 
Papers given were as follows: 
Officine Galileo (Dr. Elena Ricci), Italy, Methods and Equipment for control 
of distortion and classification of the principal point of photogrammetric 
objectives. 
G. C. Tewinkel, U.S.A., Adjustment and Calibration of the Nine-Lens Camera 
of the U.S. Coast and Geodetic Survey. 
J. Cruset, France, Study of image movement effects on aerial photographs. 
H. Kasper, Switzerland, Loss of illumination of wide angle objectives. 
J. Cruset, France. The Group of the photographic squadrons of the National 
Geographic Institute. 
R. David, Switzerland, Notes on the Wild Aviogon objective. 
Papers read by title were: 
J. E. Odle, England, Developments in photogrammetric plotting apparatus. 
Third Session, Monday, 8 September, 1952. 9.00 tot 10.40 a.m. 
Papers given were as follows: 
N. Jones, Canada, Atmospheric conditioning for air film exposure. 
A Frey Samsioe and P. H. Tham, Sweden, New investigations of curved focal 
plates. 
F. Bouwers and J. J. Van der Sande, Netherlands, Aerial cameras with mirror 
optics. 
S. Jowitt, Canada, Radar profile methods (a film). 
J. Cruset, France, Realization, utilization, and applications of simultaneous 
electronic control device for two cameras aboard two airplanes flying together. 
H. Kasper, Switzerland, Improvements of Wild aerial cameras. 
Papers read by title were as follows: 
K. Killian, Austria, The application of the gyro to aerial photogrammetry. 
J. E. R. Ross, Canada, Shoran operations in Canada. 
After the reading of papers at this session, there was time available for 
discussion. Dr. Howlett asked for questions or remarks related to the papers 
given that day or at previous sessions. 
Dr. P. Tham: Dr. Tham had found a point which required clarification in 
connection with his use of the lens distortion curve in computing curved plates. 
He pointed out that by SeidePs equation the lens distortion curve represents 
an odd function with the first term linear and the point of inflection of the 
curve at the origin. Various choices of camera constant (principal distance) 
represented various addition to the first linear term. A tangent may be drawn 
to the curve at the origin and it will in general make some angle with the 
x-axis. However, for a particular value of the camera constant the curve is 
tangent to the x-axis at the origin. This is the camera constant which he 
wished to select. 
Dr. Tham went on to explain with the use of slides the procedure for