|
16.5 Experimental measurements of turbulence effects
16.6 Calculation of Cm from temperature gradient data
16.7 Discussion
References
17. FIELD THRESHOLDS
Having considered the properties of the human eye, copious data on the
threshold functions for progressively more complex stimulus presentation in the
laboratory, the properties of visual aids and simulation media and the optical
properties of the atmosphere, it is time to look at threshold visual performance
in the field and attempts to correlate this with laboratory threshold data. In
addition, in this final chapter, we shall be considering attempts to bring field
situations into the laboratory by simulation. In carrying out such a survey, the
author has chosen to draw primarily from data concerned with the acquisition of
objects on the ground from the air and of aircraft from the ground, since such
studies are close to his own experience. However, much of the literature
concerned with such field thresholds is subject to some restriction on general
availability. It is only possible, therefore, to provide limited references and
examples. Nevertheless, it is hoped that the examples and experience summarised
will permit the reader to extrapolate to other situations possibly closer to
his own field of interest.
For convenience, the studies to be discussed may be divided into two distinct
categories - air / ground approach studies (characterised, in general, by size
growth of an object of interest in cluttered surroundings with fixed scene
|
