Re: Aerial hyperstereos

[P3D Dr. George A. Themelis <fj834@xxxxxxxxxxxxxxxxxxxxx>]

Prof. Mugnier writes:

>Standard aerial photography is flown for a nominal 60% forward overlap. 
>
>Best spacing for hyper out of a plane's window?  Take one, watch the overlap
>coverage and punch another after 40%, and so on and so forth.  If you don't
>want to take a whole series of continuous photos; only two, then after that
>40% passes (which is based on the plane's speed and the focal length of the 
>lens) - rotate the aim of the camera to get 100% coverage (slight keystone).

A few questions:

1. What is the justification of the 60 overlap?  Does it come for
experience for good topographical relief or is it related to the way the
pairs are viewed & analyzed?  Is it independent of the distance from the
ground?

2. Given that 60 overlap will force the slide film user to mount full frame
slides in 5p or even 4p mounts, do you recommend convergence?  How slight
is the resulting keystoning? 

George Themelis


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