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——— OR 
AA E E a AERE AA 
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f 
time, work is proceeding on the 1956 pro- 
ject, which covers an area of 100,000 
square miles. (See fig. 1) 
During these four years of operation, 
considerable practical experience has been 
gained which is a sufficient base for evalu- 
ation of the accuracy and economy of this 
method. 
It is not intended to discuss in this paper 
the purely instrumental problems, since 
they belong to the field of electronics, but 
to describe the basic functions of the equip- 
ment and of the method in general, and to 
discuss in more detail the application to 
photogrammetry of the data obtained by 
Shoran. 
GENERAL DESCRIPTION OF 
SHORAN EQUIPMENT: 
The basic Shoran equipment (fig. 2) 
consists of a pulse generator, a transmitter, 
and a receiver installed in the airplane, 
and a receiver coupled to a transmitter at 
each ground station. The airborne set 
measures very accurately the time elapsed 
between the moment in which a pulse is 
transmitted to the ground station and the 
moment in which the return pulse is 
received. The pulses are transmitted to the 
two ground stations on 230 and 250 mega- 
cycle frequencies. The ground set (fig. 2A) 
returns the pulse received from the air- 
craft on a common frequency of 300 mega- 
cycles. The velocity of electromagnetic 
radiation is well known for all frequencies 
and all indices of refraction, being about 
that of the speed of light. Since Shoran 
measures the loop travel, the time interval 
measuring system is constructed in such a 
way that for each 1/1000 second interval 
between transmission and reception of a 
pulse the scale reads 93.1095 miles. There- 
fore, one cycle of a frequency of 93.1095 
k. c. corresponds to the time which a pulse 
requires to travel one loop mile. The tim- 
ing oscillator of the airborne set operates 
at this frequency. 
  
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LS MANITOBA | 
  
SHORAN CONTROL 
  
  
  
BRITISH $ ! COMPLETED BY 
COLUMBIA / ALBERTA | CANADIAN AERO SERVICE LTD, OTTAWA, ONT. 
/ j H AY SPARTAN AIR SERVICES LTD, OTTAWA, ONT. 
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Figure 1: Shoran operations in Canada 
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