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Predicting the Difficulty of Locating Targets from Judgments of Image Characteristics

Report Number: AMRL TDR 64-19
Author(s): Fen Rhodes
Corporate Author: Aerospace Medical Research Laboratories
Laboratory: Behavioral Sciences Laboratory
Date of Publication: 1964-03
Pages: 59
Contract: Laboratory Research - No Contract
Project: None Given
PB Number: PB126711
AD Number: AD0601375

Judgments of 12 characteristics of 200 aerial reconnaissance photographs, each containing a designated target, and physical measures of target size and location were related to (1) search time required to locate targets and (2) judged overall target difficulty. Twenty photointerpreters and 20 college students served as subjects. Photographs were divided into two equal groups to permit cross validation of results. A factor analysis of the data, including the two criterion measures, resulted in the extraction of eight orthogonal factors. These were identified as (1) target size, (2) picture sharpness and contrast, (3) picture detail, (4) logical restrictions on possible target location, (5) target shape and pattern, (6) target location, (7) target isolation, and (8) rater bias. Linear multiple-regression analysis yielded correlation coefficients ranging from .75 to .87 for predicting the logarithm of search time and .87 to .90 for predicting judged target difficulty from the 12 psychophysical judgments and the 2 physical measures. Cross validation of obtained prediction equations resulted in average correlations of .67 and .79 for search time and judged difficulty respectively. Raters were able to make highly reliable and seemingly valid judgments about complex perceptual characteristics of aerial photographs. There was no difference in reliability of validity between ratings made by photointerpreters and those made by untrained students.

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