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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.
