31
reduce once more all the obtained raw data. There is good
reason to expect that the mean error of the triangulation
will be slightly reduced, bringing the computed value in
closer agreement with the theoretical value, and that the
distribution of the residuals will follow more closely the
theoretical distribution law.
Resume
In its present state of development satellite triangula
tion is capable of determining a single station to satellite
direction, relative to the Right Ascension-Declination
system, with an accuracy of one part in 500,000, or +01'*+.
With sufficient redundancy in the observations statistical
improvement by a factor of two can be justified, so that
the attainable accuracy of the final results, in terms of
the computed station coordinates, will therefore be one part
per million of the average station-satellite distance.
Stated in more general terms, the results already obtained
suggest that it is possible to maintain high performance
standards in all phases of a photogrammetric program even
though data acquisition covers a period of years and encom
passes the whole earth and is therefore influenced by a
significant range of environmental conditions, both geo
graphical and seasonal. Specifically, the results indicate
that large-scale data reduction activities can be carried out
over such extended periods in compliance with pre-established
performance tolerances and meet the demands for calibrating
evaluation equipment, including the control of its physical
environment, and furthermore cope with the consequences of
the turnover in manpower and unavoidable changes in organi
zational elements of the program supervision.
With respect to specific photogrammetrie operations or
components the results show a significant difference in
performance between the members of a group of comparator
operators, suggesting, at least in theory, that the use of
automatic measuring equipment could effect an improvement
by normalizing the precision of the measuring operation. On
the other hand, the results prove that each operator per
forms reliably at his own average performance level, essen
tially free of systematic errors. The histogram of Figure 10
displays the measuring errors of a group of 34 operators,
involving approximately 14,000 hours of comparator operation
and close to 1.3 million settings on about 900 plates. The
histogram shows convincingly that the work of the group as a
whole can be considered as the work of a fictitious single
operator, performing almost ideally according to the principle