Se 
1. INTR( 
Li. Ti 
fixing syst 
authorities 
will be far 
general ch 
purposes, | 
survey ope 
L2 Tt 
users and t 
roles, is ye 
secondary- 
and elsewh 
of its pote 
by Decca | 
objects of 
connection 
2. ORIG] 
241. Th 
war by an 
with H. F. 
British. Adi 
the Decca 
principal n. 
the mediur 
France, Ge 
Sweden), s 
no less tha 
tionised by 
‘repeatabili 
22. At 
as an aid to 
field—a fac 
some 200 a 
turbine Vic 
their intent 
underlying : 
later, to thi 
Decca's spe 
Waves used 
helicopters.