299
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DATA FLOW AND INTEGRATION
The NOS camera calibration system consists of several distinct
phases, starting with image coordinate measurements of collimator
targets on the calibration plates and ending with storage of
calibration data in the data base of the IDPF. The data flow for the
whole process is illustrated in figure 2.
The three main phases in the data flow are the measurements of image
coordinates, data reduction for camera calibration parameters, and
storage of calibration data into the IDPF data base.
Initial development of the NOS camera calibration system consisted of
experimenting and testing each of the several distinct processes of
operation involved in the system. The first process is the imaging
process. In this process, a single exposure of camera fiducial marks
is made followed by a uniformly distributed pattern of collimator
images from multiple exposures in a multicollimator on a single
photographic plate called the calibration plate. The next process is
that of mensuration. In this process, measurements of plate
coordinates of fiducial marks and collimator images on the
calibration plate are made either off-line on a high accuracy
comparator or on the IDPF itself. This process is followed by
photogrammetric data reduction. In this process, least squares
adjustment computations are performed either off-line or on the IDPF
to obtain camera calibration parameters. In the analysis process,
the results are reviewed using a hard copy or a terminal for
acceptance or rejection of calibration results. In the final data
base storage process, the results, upon acceptance, are stored into
the IDPF data base for future use in production.
First Phase of Integration
The next logical step in the development of the camera calibration
system is the integration of all of the various processes involved in
the system into a unified process. This approach is adopted to
insure data integrity. Statistical and computer technology methods
are used in the integration of the processes. During the mensuration
process, statistical controls are applied to obtain image coordinate
data. In the case of data entry, such as for auxiliary data required
for the calibration program, operation is tightly controlled by menus
and screen driven user interfaces, thereby practically eliminating
chances of introducing human errors. Interfaces for input/output
compatibility between various programs in the data flow are employed
to maintain the integrity of the data. Other advantages are reduced
processing time and minimal dependency on operator's knowledge of
the various processes within the system.
Final Phase of Integration
The final phase of integration consists of operating the camera
calibration system, developed in the first phase, on the IDPF. The
only consideration in the use of the IDPF is the system accuracy
which depends on the accuracy of its analytical plotter. For
instance, some of the highly accurate comparator systems, such as the
MASC (Mann Automatic Stellar Comparator), claim submicrometer
measurement accuracy as compared to 1 to 2 micrometers of the IDPF
analytical plotter.
