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Systems for data processing, anaylsis and representation

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Helava SOCET SET. Other systems are being
considered for testing as well.
This paper summarizes preliminary results of
investigating the utility of using softcopy
photogrammetric systems in place of selected
WisDOT mapping operations. The evaluation
concept, strategy, and results can be generalized
for other agencies of similar production
The evaluation project is designed to address:
a) Functions and Operational Characteristics:
These include software, such as input/output,
orientation procedures, and extraction; hardware,
such as mono and stereo viewing, floating mark
operations and coordinate measurements, memory,
and storage capacity; and other system related
operational requirements, such as user interface.
b) Accuracy: To determine if automated DTM
extraction techniques do actually attain acceptable
accuracies, the following tests have been devised
for this purpose.
- Comparing DTM generated by softcopy system
automated correlation methods, against DTM
generated manually by a WisDOT operator using
conventional plotters.
- Comparing DTM generated by softcopy system
automated correlation methods, against DTM
generated manually by a WisDOT operator using
same softcopy system.
The WisDOT mapping accuracy standards require
that error must not exceed 0.3 inch for 100% of
direct observations, and same for at least 90% of
indirect observations.
C) Speed: A substantial gain in time can be
achieved if the accuracy attained by automated
extraction methods are higher or at least
comparable to that normally attained by an
experienced photogrammetric operator.
Another criterion is defined by operator-system
interaction time required for a full end-to-end
stereophotogrammetric process. Interaction time
is observed in the softcopy systems and compared
with existing WisDOT standards for a typical
mapping operation.
3.1 Data Management
The images used in this project were scanned in
22.5, 15, and 12.5 microns. The file sizes ranged
340+, 235+, and 100+ megabytes. This range
of data volumes requires significant storage
capabilities. There are some options to deal with
such extensive amount of data for production
environment. These include options such as
central data bank, local area network, etc.
3.2 Eye Fatigue
The Intergraph and Helava systems utilize two
different technologies for stereo viewing. In both
cases, however, the WisDOT operators
commissioned to examine the systems on site, Le.,
UW Softcopy Photogrammetry Lab, expressed eye
fatigue shortly after they used the systems. These
operators were trained on, and routinely used,
stereoscopic vision with optical components with
continuous-tone hardcopy media. Optics of most
conventional photogrammetric machines tend to be
of high quality and craftsmanship, and hence very
expensive. This is to ensure best visual quality,
geometric accuracy, and above all, to enable the
operator's eyes hours of focusing with minimal
exhaustion. This can be generalized with
operators of any conventional photogrammetric
production facility. It is anticipated, however, that
eye fatigue would be reduced as operators get used
to the systems.
3.3 Accuracy
Comparing DTM generated manually by a DOT
operator, using conventional plotter, against an
automatically extracted DTM.
Model 1:
No. of DTM points Compared: 3046
Average Error Calculated: 0.7067 ft.
Standard Deviation: 1.063
Model 2:
Comparing DTM generated manually by a DOT
operator, using Helava system, against two
automatically extracted Comparing. Each was