"E 
| 
| 
E 
IE 
| 
| 
PSN 
e EIS 
E ET 
  
   
/ 
‘ A / / 
NAVIGATORS' GONDOLA— A 
CAMERA ———— vi 
SHORAN INDICATOR & RECORDER—————— —— 
SUM & DIFFERENCE OR 
STRAIGHT LINE PLOTTING TABLE———— —— — — 
SHORAN DIPOLE — = 
  
A 
^ 
/ 
  
77 T sa 
FA 
a us RADAR ALTIMETER 
  
    
Figure 3: Shoran installation for York aircraft 
presents directly as miles on the counter 
the difference between the "zero" reading 
and the phase advance. Thus, the trans- 
mission time is measured, not directly, but 
by the phase advance required to make the 
received signal synchronize with the marker 
pulse; and this time interval is read in 
terms of equivalent miles and fractions. 
Fig. 3 shows an installation of Shoran in 
a York aircraft. 
STAGES IN REDUCTION 
OF SHORAN DATA: 
All factors which introduce variables in 
the measurement of a Shoran distance can 
be divided into three groups: 
1. Errors caused by the equipment itself. 
To this group belongs the so-called “delay”, 
which is the time taken by the pulse 
received by the ground station to go 
through the electronic chain of the ground 
station and be retransmitted. The delay is 
determined empirically by measuring a 
series of known distances. The operation 
of delay determination is called ground 
calibration. The calibration of Shoran 
equipment is performed at the beginning 
and end of each Shoran operation. 
2. Errors caused by specific atmospheric 
conditions existing during each Shoran 
survey. The velocity of the electromagnetic 
waves and the shape of the Shoran path 
depend upon the atmospheric conditions 
during a Shoran survey. First, based on the 
atmospheric data, the correction of the ray 
path must be determined and applied to 
reduce the ray distance to a chord distance. 
Then, since the distances given by Shoran 
are based on a standard wave velocity, a 
velocity correction depending on atmo- 
spheric conditions must be determined and 
applied to the Shoran reading so the cor- 
rected distance will give the true chord 
length. 
3. Influence of the altitude of the aircraft 
and the ground stations. The elevations of 
the ground stations are determined by pre- 
cise barometric observations. The altitude 
of the airplane is also precisely determined 
from altimeter readings under careful 
consideration of atmospheric conditions. 
Knowing the elevation of the ground sta- 
tions (antennas) and the altitude of the 
airplane, the chord length can be reduced 
to geodetic distances and then to map 
distances. 
To determine the atmospheric conditions 
during each Shoran flight, weather sound- 
ings and systematic meteorological obser- 
vations are made in the area concerned. A 
more detailed description of reduction 
procedure of the Shoran observations is 
given iu references (5), (6), and (8) at 
the end of this paper. 
| 
METHOD: 
ZONTAL 
1. Establis/ 
geodetic p 
For photog 
area, a net 
required. G 
by the Shc 
has replac 
method in 
areas. Thes 
of 200 mil 
distances ai 
in precise 
tion, a tria 
angle is t 
chain. In ti 
by side-sid 
redundant 
quadrilater 
F; gu 
between px 
horan "Li 
The airc 
measured a 
simultaneoi 
tance to ea