Water Current Measurement by Tidal Cycle Photography 
by 
H. L. Cameron 
Director, Photogrammetry and Geology Division 
Nova Scotia Research Foundation 
Introduction: 
The strong tidal currents in Petit Passage and 
Grand Passage, two narrow straits in western Nova Scotia 
near the entrance to the Bay of Fundy make pier and other 
harbour construction difficult to plan and maintain (Fig. 1) 
As an aid to engineering planning the two straits 
were photographed every fifteen minutes throughout a 
complete tidal cycle. That is, from low to high tide and 
from high to low tide, 86 strips in all being taken. This 
required two sorties which were separated by six months in 
time, because of the exigencies of weather and availability 
of aircraft. The photography was carried out by 408 Squadron 
R.C.A.F. Rockcliffe, at the request of the Dominion Public 
Works Department of Canada. 
The methedyof water current measurement by 
anomalous parallax was used to plot the position and 
velocities of current maxima. Forty six maps of Petit 
Passage have been prepared, and, when taken in groups on a 
light table, show the swing of the current at various times 
during the tidal cycle. Counter currents and eddies were 
mapped and their life spans and positions provide much 
interesting and useful data for both engineers and 
fishermen. The main value of this technique lies in the 
synoptic picture of the currents and eddies, which it 
provides. 
Equipment and Techniques: 
408 Squadron R.C.A.F. Rockcliffe Base carried 
out the photography on November 23, 1958 and April 13, 1959, 
A Lancaster bomber, modified for long range photography, 
was used from R.C.A.F. Greenwood Base, which is located 
(1) Cameron, H. L., 1952 "The Measurement of Water Current 
Velocities by Parallax llethods™, Photogrammetric 
Engineering, (arch 1952, pp 99-104