Carl 
Scope 
view 
. The 
k has 
lator 
image 
desk 
tions 
ished 
EREO- 
nical 
d the 
ussed 
ed to 
This 
tape 
pe is 
atter 
ation 
rans- 
mpute 
ware. 
  
wl, (02 are required as parameters for this coordinate trans- 
formation. Except for the camera focal length which is generally 
known, all these parameters can be determined directly on the 
air photos, provided that the terrain coordinates of at least 
three control points are known. These parameters are computed 
with the aid of the orientation programs which are an essential 
component of the software. 
3. Uses o f the Stereocordàá4 
Viewing the two photographs through the stereoscope, the 
operator sees a three-dimensional model of the terrain together 
with a floating mark which can be placed on any desired point 
within the stereo model (figure 2). The desk calculator then 
computes the terrain coordinates of the point on which the 
floating mark has been placed. The machine thus primarily serves 
to determine the coordinates of individual points. However, if 
several points are set in direct succession, other quantities 
can likewise be measured with the aid of suitable computer 
programs. These are: 
Horizontal distances and distances in space. 
Level differences (for instance, height of buildings or trees). 
Slope angles (for instance, of hillsides). 
Azimuth angles (for instance, of geological features). 
Dip and strike angles of geological strata (provided that 
the stratum is visible at a minimum of three points). 
Planimetric and surface areas. 
Volume (for instance, of cut and fill, projected dams etc.). 
p ! STEREOSCOPE 
AERIAL = Ea 
| 
PHOTOGRAPHS 
STEREO MODEL 
SURFACE 
AREA VOLUME 
DIP & STRIKE ANGLE 
OTS) 
XN 
A AR 
AZIMUTH ANGLE ; 2 
A - Ss 
SPATIAL N | 
DISTANCE AM 
eei "i 
' 
SLOPE ANGLE 
    
      
   
    
    
  
VERTICAL 
DISTANCE 
Fig.2: Measuring 
from a stereo model