PHOTOGRAMMETRIC ENGINEERING 
5 
carry method of extending vertical control while photography is being taken. It 
is hoped that isobaric surfaces at higher elevations will serve as a datum from 
which the radio altimeter can measure down to terrain. The result should be a 
profile under the plane with both ends of the course tied to a known elevation 
such as a lake surface. Horizontal position would be provided by Shoran and 
other methods under development (Figure 2). 
The problem of directing the photographer’s aircraft on a straight and paral 
lel flight line to assure complete coverage can be solved by Shoran combined 
with the system in an airborne gadget which literally forces the pilot to fly the 
correct course via PD I needle (Figures 3, 4, and 5). Experimental flights have 
also been made with a quick-process camera mounted obliquely and photograph 
ing check points on the next flight line. A 250-mile flight from Dayton to Pitts 
burgh was made with this simple and ingenious method. Photos taken on one 
flight line are used by the navigator to stay on the next, adjacent line (Figures 
6 and 7). 
It must be thoroughly understood that all problems have not been solved. 
Several knotty ones still remaining are: 
a. Charting through darkness and obscurity. 
b. Precise transfer of a horizontal position “fix” in an aircraft to the nadir 
point on the ground below. 
c. Automatic or semi-automatic means, preferably electronic, of plotting 
contours from near vertical photography. 
In conclusion, I recommend that you examine our exhibits illustrating an 
overlap control system using the bombsight, a new 9 X18 inch photo oblique 
alidade, a new method of representing relief on charts, as well as a most interest 
ing Aerial Photographic and Charting Service display.