In addition, a Printronix line printer can be directly connected to 
the Tektronix computer. Figure 2 shows a total view of the system in 
cluding a Zeiss Planitop F2 stereoplotter. 
Figure 2. 
Total view of the 
system with Zeiss 
Planitop F2 
First experience with the system in mensuration phase has indicated 
that, despite the minimal hardware configuration, photogrammetric data 
can be digitized in a user-friendly way, immediately be verified and 
corrected on the screen by means of a set of properly defined functions, 
and stored on tape cassette in a sequential file. Although programs as 
well as data must be stored on the same cassette, it seems that its 
capacity of 450 kByte is sufficient to hold the data for one stereo 
model. For real practical use, however, an additional external tape 
cassette drive only for data would be essential. 
Interestingly, the non-dynamic storage tube type display of the Tektron 
ix 4054 has not given rise to any serious discomfort. It is true, of 
course, that selective erasing or changing of graphical objects in parts 
of the screen is impossible. This disadvantage, however, is largely 
overcome by the fact that the entire picture can easily be re-displayed 
with the altered data. An enormous advantage of the big screen is its 
high resolution which is unparalleled by raster-type displays, at least 
within a comparable price-range. 
The present hardware configuration is definitely insufficient for the 
model phase. There, real interactive work is virtually impossible due 
to the low data transfer rate of the cassette (1 kByte/s). Either flopp 
ies (5 kByte/2) or additional external RAM memory modules (50 kByte/s !) 
with a capacity of 1 - 2 MByte are needed. For the block phase both 
RAM's and large disk drives are essential. These peripherals have not 
been considered for the experimental set-up, partly due to high costs, 
partly because a direct link to the university's computing center is 
being planned. The latter solution avoids incompatibility problems and 
enables large sets of data to be processed on the mainframe. In this 
case the Tektronix 4054 is identical to a 4014-terminal. 
SOFTWARE CONFIGURATION 
The software of the experimental set-up consists of: 
* BASIC interpreter incorporated in the 4054 computer 
* Fundamental graphics software integrated into BASIC