324 
above) are supplied by the selected vendors for this equipment. The 
technology surrounding these three components are governed by the 
forces that shape developments in the general field of Automatic Data 
Processing (ADP) and far beyond the influence of the photogrammetrie 
community. The best that a photogrammetric system designer can hope 
for is to configure his development in a way that allows for timely 
benefit from the continuous advances in ADP products and services. 
The tendency in the ADP field is toward open system standards which 
in time will benefit the photogrammetric community. 
The ADP situation relative to the fourth component of the PWS (the 
stereoviewer) is quite different. The size of the photogrammetric 
hardware market worldwide is too small to provide competitive 
incentives for promoting standardized interfaces for stereoviewers. 
The lack of such standards is making the mixing of hardware from 
various manufacturers into a single functioning production 
environment a task burdened with high risk and uncontrolled cost. 
For this reason, it was decided that a primary goal of IDPF will be 
to greatly reduce or eliminate dependency on any specific type of 
stereoviewer hardware configuration. The rest of this paper will be 
devoted to the description of how this goal was accomplished. 
IDPF STANDARD INTERFACE 
IDPF interfaces to any stereoviewer through a standard interface 
which has two main components. (See fig. 2.) The first of these 
components is the Virtual Photogrammetric Stereoviewer (VPSV) and the 
second is the Mapper. The VPSV is an idealized conceptualization of 
a stereoviewer with extensive capabilities. All existing and 
anticipated future viewers have capabilities which can be represented 
by VPSV. This includes digital stereoviewers as well. The 
components of VPSV, which are shown in figure 3, are as follows: 
o Two image stages 
o A bank of valuator dials 
o Control panel of binary switches 
o Audible signal device 
The Mapper (fig. 2) is a set of tables which are required to map all 
computer controlled facilities for a specific stereoviewer hardware 
into the VPSV. The mapper is, therefore, hardware specific and it is 
the only software development that is required for IDPF to interface 
to any stereoviewer which complies with the standards. 
Figure 2.—Virtual photogrammetric stereoviewer components.