192 THE CANADIAN SURVEYOR May, 1960 
Fıc. 5a 
  
Test oN “A” Wing Date: 16 Dec. 59 
Grid: f/18 at one minute 
Object: f/36 at one minute 
Length of base: 18 cm 
Nominal magnification: 2X 
Distance from lens to grid: 48.7 cm 
Distance from lens to 
base plate: 52.1 cm 
Fic. 6 
MEASUREMENT OF Win TUNNEL Mopezs 
Photogrammetry is also being used to check the dimensions of wind tunnel models 
for aerodynamic investigations. There are no photogrammetric cameras for this pur- 
pose, and a method has been developed at N.R.C. to show the usefulness of photo- 
grammetric measurements. A rectifier is used as a camera, double exposures are made 
to get the object image and the image of a precision grid on the same photograph, and 
a base is obtained by shifting the object-grid combination. This grid image makes it 
possible to observe deformations in the model. Figure 6 shows the object-grid combi- 
nation.