PROGRESS IN THE SPECIFICATION AND 
ANALYSIS OF IMAGE QUALITY 
R. Welch 
ABSTRACT 
In the four years since the XII Congress OTF/MTF procedures have 
been successfully demonstrated for the evaluation of photographic and 
electro-optical sensor system performance and "Guidelines for Measuring 
Camera System MTF's" prepared. The reliability of predicted and measured 
photographic system MTF's is influenced by variations in component MTF's, 
non-linearity of the photographic process, target fidelity and micro- 
densitometer parameters. Generally, however, predicted MTF's have been 
found to correspond to within 10 to 15 percent of measured values, and 
this is adequate for system evaluation purposes. Specifications of per- 
formance for the current and planned LANDSAT sensors are considered in 
terms of MTF, IFOV and EIFOV and compared to Skylab photographic systems. 
Based on these analyses it appears that the 30 m IFOV planned for the 
Thematic Mapper of the LANDSAT Follow-On program will result in images 
of comparable quality to those recorded by the Skylab S-190A MPF. Because 
of rapid developments in sensor system technology, the different measures 
of performance and the requirement to relate image quality to photogram- 
metric tasks, the formation of an Image Quality Working Group is recom- 
mended. 
INTRODUCT ION 
Within Commission I, the Working Group on Optical and Modulation 
Transfer Functions (OTF/MTF) has been concerned with the application of 
these measures of performance to photogrammetric problems (Norton, 1975). 
For example, both OTF and MTF's are used extensively in the design and 
analysis of imaging systems and one of the primary concerns of the Working 
Group has been to document standards for OTF/MTF measurement procedures 
so as to insure comparability of results between laboratories testing 
wide-angle photogrammetric camera lenses. These problems are considered 
in further detail by Norton, Brock and Welch (1976), and by Martin (1976), 
Rosenbruch (1976) and Tiziani (1976). 
The procedures by which operational system performance can be 
evaluated without resorting to direct resolution tests have also been of 
interest to the Working Group. Photogrammetrists and earth scientists 
use image quality criteria to judge the potential applications of remote 
sensor data and methods are required for the reliable prediction and measure- 
ment of operational system performance. These considerations led the previous 
Working Group to recommend the continuation of investigations of MTF ana- 
lysis techniques, with particular emphasis on edge gradient analysis (EGA) 
(De Belder, Jones, Sorem and Welander, 1972). Interest was also expressed 
in the standardization of MTF analysis procedures and the establishment of 
tolerances for precision and accuracy. 
As a consequence of these recommendations, "Guidelines for Measuring 
Camera System MTF's," (Table I) were developed and incorporated in the