he = 0,035 o v o d ° sin & insifez 
in which 
v is the air speed in mopoho, 
d is the distance from the initial point, 
oLis the angle of drift, and 
pis the latitude (approx). 
To the second group belong various sources of error 
of an instrumental or more general nature which are inherent 
in the physical process of electronically méasuring the 
distances between an aircraft and corresponding profiie points. We 
shall mention oniy a few of them here. Because of the 
dimensions of the electro-magnetic beam (a cone with a vertex 
angle of 1.5 g.) a fairly wide area, rather than one specific 
point, is involved in the measurement of the distance. For 
example, at an altitude of 2000 meters (6500 feet], the area 
involved would be equivalent to that of a circle having a radius 
of about 26 meters (about 85 feet). It must also be borne in 
mind that the radiation is generally not exactly perpendicular 
so that the identification of the profile in the field is not 
entirely without ambiguity. Gyro stabilization of the beam and 
the 35 mm. camera plotting the course of the profile in the 
field, which was introduced by the Photographic Survey Corporation 
of Toronto, represents a step forward in this respect. Further 
errors may be the result of variations in the strength of the 
energy reflected from the earth (e.g., variations between the 
energy reflected from water surfaces and that from dry land); of 
partial penetration of the tree-tops, or of the limited resolving 
power of the radar profile, etc. 
In addition to the sources of error mentioned above, we 
might mention identification errors which may lead to incorrect 
correlation of the radar profile with a corresponding point on the 
ground. 
Thus, with this method of measurement, as with any other, 
we are apt to encounter a number of accidental and systematic 
errors and one of the problems involved in the application of the 
radar profile method to photogrammetry is the necessity of 
eliminating as many of these errors as possible from the mapping 
process. 
With this brief outline, we now turn to the application 
of the radar profile to photogrammetric mapping and to the results 
obtained thus far. 
One of the first occasions on which the radar profile 
method was applied on a large scale was in connection with an 
extensive mapping project undertaken by the Aeronautical Charts