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darcl Atmosphere. There being several well known standard atmospheres 
(like US Standard, ARDC Standard and ICAO Standard) controversy persists, 
although all these are practically the same up to about 20 km flying 
height. Satisfactory concepts in this respect with regard to oblique 
photography and satellite imageries are yet to be developed. 
The problem of Image Motion Compensation (IMC) remained unsolved 
until Kawachi (1965) derived the formulas with regard to onlv the rotation 
al movements and certain corrective (although partial) approaches were 
developed to provide film or camera movements during exposure by using one 
of several IMC devices. The complexities has been resolved by Ghosh (1985) 
through augmenting the collinearity condition equations. This approach is 
fully computational. 
6.2.3.3 Related to Stereo Images 
It was around 1953 that the analog concept of relative orientation 
by way of elimination of y-parallax evolved into the condition of coplanar- 
itv through the efforts of Schut (1956-57) at the National Research Council 
of Canada. This condition implies that the two perspective centers (or 
exposure stations), any object point and the corresponding image points on 
the two conjugate (overlapping) photographs of the stereo-pair must all 
lie in a common plane (Ghosh 1988). This condition is fundamental to 
relative orientation or space intersection. Like the collinearity equa 
tions, this condition equation is also non-linear and need to be linearized 
(for computer utilization) with iterative solutions in mind. The relative 
orientation formulation developed by E.H. Thompson (1959) showed complete 
elimination of trigonometric functions with a consequent ease and speed of 
computer utilization. Separately, Paul Herget in developing a system of 
analytical control extension, by using vector notation, minimized the 
perpendicular distances betxveen pairs of corresponding rays in order to 
achieve a solution for relative orientation. He employed an ingenious 
trick whereby ground control equations took the same form as relative 
orientation equations (Herget and Mahoney 1957). 
On the other hand, the superiority of the numerical relative orien 
tation (over empirical and graphical methods) was definitively established. 
Also were established the processus of improving such relative orientations 
(Ghosh 1964). Notwithstanding the analytical conditions of collinearity 
and coplanarity, the on-line solutions at analytical plotters are all 
developed practically around such analogical-numerical concepts. 
The process of absolute orientation (i.e. scaling, translating and 
leveling of a stereo model with respect to a ground reference coordinate 
system) is simply a problem of coordinate transformation. The equation 
must be linearized before it can be used. The method of least squares may 
also be used. This approach was standard already by the early 1950s. 
It was readily found that during a sequential procedure of aero- 
triangulation the scale of a previous model needs to be transferred to the 
next model. This is similar to the requirements of the analog aeropolvgon 
method. This process was mathematically modeled at the NRC Canada (Schut 
1956-57) and is known as the scale restraint condition. This condition 
implies that with regard to a point in the triple overlap area (i.e. area