^u 
is discussed. The Working Group proposes quality assessments, based mainly on MTFs, to be compared with 
standard deviations of photogrammetric measurements and interpretation response values. 
38. Welch, R. 
United States 
MODULATION TRANSFER FUNCTIONS 
The subject of modulation transfer functions (MTF's) of photogrammetric camera systems has received very 
little attention to date because of the complexity of undertaking the required measurements and the largely 
undemonstrated value of MTF's to the practical photogrammetrist. However, MTF analysis is used extensively 
in camera system design and can be expected to play an important rold in the development of future 
photogrammetric camera systems. Consequently, in order to judge the improvements in image quality likely 
to result from new designs, it is first important to establish the MTF's of photogrammetric camera systems in 
current use and the relation of these MTF's to image quality. The practical considerations in determining 
MTF's include the design of targets, specification of photographic parameters and evaluation equipment, and 
the methods of evaluation. Each of these considerations is discussed, with particular emphasis given to an 
inexpensive but accurate graphical-digital method of MTF analysis of the images of edge targets. 
39. Welch, R. 
United States 
QUALITY AND APPLICATIONS OF AEROSPACE IMAGERY 
Experiments with laboratory and aerial photographs in combination with theoretical considerations have 
compared the imaging characteristic of photogrammetric camera systems with those of reconnaissance, 
multispectral, and return beam vidicon (RBV) systems considered for aerospace use. From these experiments 
it is estimated that photogrammetric cameras in combination with high-quality reconnaissance films will 
provide low-contract resolutions to approximately 80 £ /mm, and detectability and measurability thresholds 
of about 10 44m and 20 jm. These cameras and films can be used for high-altitude aerial photography with 
performances comparable to those of reconnaissance and multispectral systems. To provide space photographs 
of similar quality, metric cameras without image motion compensation would need apertures of f/4 or larger, 
and high-resolution film speeds would have to be increased by a factor of 2 or more. However, it is possible 
to use currently available photogrammetric camera systems in place of reconnaissance systems to obtain space 
photographs of good quality to about 1:380,000 scale. These photographs would be suitable for the compilation 
of planimetric maps to 1:24,000 scale, if adequate viewing magnification were available in the plotting 
instrument. Furthermore, such photographs could also be used for the establishment of supplemental control, 
production of photomaps and reasonably detailed studies of earth resources. The economic benefits of using 
smaller scale imagery for mapping tasks include the replacement of several older plotting machines by one 
precision mechanical-projection or analytical instrument of greater versatility and accuracy. These latter 
instruments could be used with either high-altitude or space photographs for the direct compilation of maps 
at a wide range of scales. Detailed earth resources studies are feasible with improved high-altitude aerial 
photographs, particularly if better color infrared films can be manufactured. As the small-scale space imagery 
to be produced by the ERTS A system will have an estimated ground resolution of 180 m at the CRT, the 
imagery will be useful for very generalized regional studies of earth resources. Skylab experiments are planned 
to provide multispectral and high-resolution photographs useful for both resource studies and photomapping. 
However, the inclusion of a metric camera in Skylab would greatly enhance its value to the cartographer. The 
future selection of photographic or RBV imaging systems will depend on the intended applications of the data 
they supply. 
40.  Ziemann, H. 
Canada 
IMAGE GEOMETRY 
Sources of changes in the image geometry during the process of imaging the earth's surface on film and during 
the following photogrammetric procedures are discussed. Recent publications on several contributing factors 
are reviewed. The results of a lens distortion investigation in which two reseau lenses were calibrated in the 
laboratory in a very elaborate way and by taking aerial photographs over a test area at scales approximately 
1:10 000 are reported. The various sources of image deformation are then discussed, using primarily the 
author's research results and results reported at the recent Conference on Image Deformation (Ottawa, June 
1971). Finally, indications are given regarding the correction of errors in the image geometry. 
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