type should 
eras intend- 
purposes. 
connaissance 
y specially 
phers, who 
10wledge of 
) be able to 
' the scope 
uipment. In 
ssance pho- 
m at work 
oto recon- 
| out on the 
ny defences 
n of ascer- 
| of fortifi- 
cted. Stereo 
sible, taken 
omatic and 
materials, 
ith suitable 
of recon- 
acements is 
dy slightly 
In summer 
films and a 
der certain 
| the naked 
me area of 
s the possi- 
ich the ob- 
placements, 
intelligence 
it possibili- 
colour and 
e carefully 
parts of the 
1e positions 
nth several 
ion in such 
After dark, 
  
  
   
    
     
n * 5 d 
Fig. 11. Detailed reconnaissance photo. Fig. 12. The positions of emplacements often 
appear very clearly in an enlarged reconnais- 
sance photo. Compare with fig. 11. 
the shutters are opened so that every gun firing within the radius of the cameras 
is recorded. The main features of the terrain are also reproduced if the shutters 
  
Fig. 13. The positions of the flanking machine guns etc. firing has been 
recorded on this night photo (taken about 11-45 p.m. in April in the central 
part of Sweden). 
The light of the tracers is diffused on account of sleet falling. 
are kept open long enough, from a few minutes to an hour depending on the 
time of year. In such cases, the muzzle flashes of single guns and the courses of 
tracers can be ascertained very accurately, and to a certain extent one can even 
cell the difference between the various types of guns. It must, however, be point- 
ed out that the illuminating of the battle-field with flash grenades and “Very