| 
5 
i 
| 
I 
Et 
AT 
; = 
  
the nadir points, or the adjusted position 
of pass points and co-ordinates of C read. 
Through a co-ordinate transformation the 
Autograph co-ordinates can be transformed 
to geodetic co-ordinates. 
The adjustment of the Shoran positions 
can be done graphically or analytically. The 
graphical method is an approximation. In 
the graphical method, a curve is drawn by 
hand in such a way that the sum of the 
negative and positive differences between 
the curve and the positions of pass points 
balance out. 
The analytical adjustment is a least 
squares adjustment. The corrections to the 
Shoran positions of the nadir points are 
computed in such a way that the sum of 
the squares of the differences between the 
adjusted position of the pass points and 
the model positions is a minimum. À de- 
tailed theory of these adjustments will be 
the subject of a special publication. Pre- 
sently Canadian Aero Service is conduct- 
ing a series of experiments to determine the 
accuracy of this method. The author feels 
that by using this method it should be pos- 
sible to determine positions with a probable 
error of +=6.5 meters. 
4. Direct use of Shoran controlled photog- 
raphy for horizontal bridging. This 
method was suggested by the Army Survey 
Establishment and is being carried out by 
Canadian Aero Service and Spartan Air 
Services. Shoran controlled photographic 
lines are flown with normal forward over- 
lap at an altitude of 20,000 ft. (giving a 
range of approximately 200 miles from 
the Shoran station) along each one degree 
of longitude and each 20 minutes of lati- 
tude (fig. 13). As a result, large areas 
are covered by relatively dense grids of 
Shoran points which are used to control 
aerial photography at a scale of 1/62,000. 
To extend the horizontal control in the 
areas located between the lines of Shoran 
controlled photography, aerotriangulation 
or slotted template methods can be used, 
depending on required accuracy. 
MODEL POSITION OF PASS POINTS 
SHORAN POSITION OF NADIR POINTS 
MODEL POSITION OF PASS POINTS 
F; gure 12 
12 
  
  
hdl 
. (Joins 2079) 
  
  
le 
  
£ 
112°