| les con- 
t par suite 
ible d'un 
et de re- 
‘, de tireuses 
andes diffi- 
srandisse- 
vorable à 
mr: 1'1.G. N. 
A Precision Vertical Reference System 
for 
Photogrammetric Applications 
Presented as a Commission I Paper at London 
Ninth International Congress of 1960 
of International Society of Photogrammetry 
by 
T. Trott 
Chief Engineer 
The Aeroflex Corporation 
Aeroflex Laboratories Division 
34-06 Skillman Avenue 
Long Island City 1, N. Y. 
U.S. A.