ANALYTICAL ON-LINE SYSTEMS IN CLOSE-RANGE PHOTOGRAMMETRY 
checks important for the acceptance of data. 
Immediately after the editing action is com- 
pleted the modified results can be rerun for 
visual inspection and otherwise graphically 
displayed. The operator monitors the proc- 
ess. 
A series of additional operations are very 
compatible with the function of an on-line 
analytical system. Auxiliary transformations 
can be applied to change the coordinate sys- 
tem forthe control ofthe floating mark motion 
in the virtual model. This is extremely useful 
in architecture (Jachimski, 1974) where mul- 
tiple facades can be plotted from a single 
model upon guiding the floating mark in gen- 
erally oriented planes fitted to individual 
walls. Computations of different geometric 
parameters, such as angles, distances, areas, 
volumes, differential changes, deformations, 
etc. represent a simple use of digitized data 
immediately after their acquisition. A more 
sophisticated data analysis can be selectively 
combined with an on-line process to enable 
surface fitting, interpolations, and statistical 
evaluations important for further operations. 
Probably one of the most useful auxiliary 
functions is provided by graphical displays 
builtas a part ofthe on-line system. A plotting 
table is elementary for any modified graphi- 
cal presentation of available data, but an in- 
teractive CRT-display is much faster and 
more powerful. With its use one can produce 
all types of projections, perspectives, slope 
maps, contour renditions, and other thematic 
plots which can be immediately modified by 
the operator to provide the most useful pre- 
sentation. Through its use additional data can 
be obtained from the on-line function. Only 
after the operator is satisfied, is the latest data 
stored or line-drawn in the final format on the 
plotting table. 
MAN-MACHINE INTERACTION 
As already mentioned, a moderately pow- 
erful minicomputer, such as one of the 
PDP-11 family, is capable of carrying and 
performing a series of basic and auxiliary 
photogrammetric programs stored together 
with the computer system monitor on a 
magnetic disk. The individual tasks and solu- 
tions can be organized into program modules 
and libraries tied by conversational programs 
into a universal photogrammetric software 
package. Its flexibility depends on built-in 
communication channels which determine 
the level of the potential man-machine in- 
teraction. 
Here, we attempt to show only some of the 
general possibilities and options which can 
be used by the system. Basically, some form 
89 
of communication with the computer is in- 
dispensable to modify the current operation 
at any level of the system performance, e.g., 
to terminate the action, to accept new infor- 
mation, to transfer control to any other func- 
tion, or to continue the previous one. The 
system invites information or specific actions 
and the operator follows accordingly. Essen- 
tial conversational patterns frequently used 
can also be prestored and the communication 
speeded up just by specifying the code of a 
particular combination of actions to be in- 
voked. 
When starting a task a selection of condi- 
tions is made out of existing options included 
in the photogrammetric software. In the 
phase of formulating the image geometry it 
must be stated what type of projection is re- 
quired, which are the known parameters, and 
which parameters are to be determined on 
the job. Further information should also be 
supplied on where to allocate the parameters, 
if they are prestored, and how to use them. In 
the phase of the model reconstruction the 
conditions and required constraints for the 
solution are specified first. Then the meas- 
urements are performed and resulting data 
recorded in a sequénce controlled by the 
operator or by the system from prestored in- 
structions. Weights for observations may be 
entered and control support specified inde- 
pendently for each data point. The routine 
can be interrupted, measurements rejected or 
repeated, and all previous settings checked 
with the use of an automatic computer- 
controlled drive. The computation is moni- 
tored by means of auxiliary printouts to show 
progress. Ultimately, a complete listing can 
be printed out or only the final accuracy as- 
sessment displayed. Computations can also 
be repeated from an edited data set or with 
added or corrected information until the re- 
construction is considered satisfactory. The 
real-time operations necessary for detailed 
photogrammetric compilation are started 
after specifying its conditions, the type of 
computer control, and other requests con- 
cause the storage, display, or editing of 
ata. 
CONCLUSIONS 
Analytical on-line systems are becoming 
more available. At the present a few new sys- 
tems are developed, which are primarily 
oriented towards an ordinary user and not to- 
wards exclusive, huge mapping agencies as 
in the past. The cost and operational com- 
plexity are expected to be moderate and the 
reliability high. 
In general, the functional range of on-line