184 
* Application programs written in BASIC by the user for the 
purpose of interactive photogrammetric digitization. 
In the following only the user's software is described in some detail. 
The present version requires a relatively and absolutely oriented 
stereomodel. Whether the orientation is performed by analog or analyt 
ical means, is immaterial. It is intended to integrate in the system 
a separate computer-assisted absolute orientation program (see Dorrer, 
1977). 
The application program for the mensuration phase is divided into an 
initialization program and the main interactive program. Together with 
two data files, these programs are stored on magnetic tape cassette 
and constitute the entire mensuration system. A third data file on the 
same tape cassette is considered to contain all digitized data in se 
quential order; it makes up for the main bulk of tape storage. The 
source code of both programs presently consist of some 600 BASIC in 
structions. During the stereocompilation process the digitized data 
are first stored into a memory buffer before they are transferred to 
the tape file. In the present version only planimetric coordinates can 
be stored. Application programs for the model and block phases have 
not been written as yet. 
Figure 3. 
Real-time loops 
for data logging 
and display