Full text: Proceedings of the Symposium on Progress in Data Processing and Analysis

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.

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