Visual Factors Affecting the Precision of Coordinate Measurement in Aerotriangulation

摘要

A study was made of the precision of centering black circular measuring marks in sharp circular targets simulating artificial pass-points with homogeneous backgrounds of different densities. An extensive review of the relevant functions of the visual system is given, and the task is related to the general area of visual acuity. The results demonstrate that the precision of pointing may be significantly affected by the size relationship between the measuring mark and pass-point, the background density, and the adaptation level, provided that the instruments used are sufficiently sensitive. The results support the proposition that subjective neural effects at edges contain significant visual information, and this would appear to be important where visual settings are being made by bringing geometrical configurations into close relationship with one another. The maximum information for the centering was contained in ribbons approximately 1 minute of arc wide around the light areas of target and measuring mark. The most precise pointings were made by selecting a measuring mark to give a minimum annulus width within these ribbons, irrespective of the target size, up to 2 degrees retinal subtense. The relationship between the standard deviation of pointing and annulus width appears to be linear for annulus widths up to approximately 1 minute of arc visual subtense. A discontinuity occurs in this vicinity, and the relationship appears to take on an exponential form. (Author)