13 
ORTHOPHOTO PRODUCTION PROCEDURE 
The Off-Line Orthophoto Printer requires profile data, 
orientation data and the input photograph to produce an 
orthophoto. At present the AS-11B-1 is being used to 
produce the orientation and profile data. It is not within 
the scope of this paper to fully describe the functions of 
the AS-11B-1 so only a simplified outline of its use will be 
presented here. (Figure 5) 
The procedure starts with orienting a stereo pair of 
the desired area, in the AS-11 analytical plotter. A model 
coordinate system is established usually at the nominal scale 
of the photography. Any desired corrections for atmospheric 
refraction and lens distortion are entered at this point. The 
photo to model orientation parameters are computed during 
relative and absolute orientation. The orientation and 
correction parameters are punched out on what is termed a 
shutdown tape and saved as an input to the OOP. The model 
is then profiled in the Y direction, profiles being simply a 
series of Z measurements of the terrain surface taken at 
regular intervals along a number of parallel evenly spaced 
lines. This data is digitized and recorded on magnetic tape 
for direct input to the OOP. The AS-11B-1 has the ability 
to automatically gather profile data using an electronic 
Correlator which greatly speeds up the data collection over 
standard manual means. The spacing between profiles is 
dependent on the accuracy desired from the orthophoto. The 
magnetic tape containing the profile data, the shutdown tape, 
and either photograph from the stereo pair are then taken to 
the OOP. The four fiducials of the input photograph are 
measured on the OOP photo carriage in order to establish the 
interior orientation. The fiducial measurements along with 
the shutdown tape are used by the OOP control system to re 
establish the photo to model orientation and make the necessary 
model to photo computations already explained. The following 
generalized steps are then taken: 
a. The output drum is initialized (i.e., set the zero x 
zepo y position). 
b. The desired print width, print speed, print scale 
(model to drum) and a light exposure are established. 
c. The model boundaries to be covered by the orthophoto 
are input.