A parallax-factor alignment chart.

Abstract

Photo-mensuration techniques are often used in obtaining elevation differences in areas where topographic maps are unavailable. These differences can be obtained with simple instruments such as the parallax wedge or the parallax bar. Although the accuracy of measurements with this equipment is not as high as that obtained with the complicated plotting instruments used in topographic mapping, past experience has shown that elevation differences can be measured within k10 percent two out of three times.

Citation

Bernstein, David A. 1960. A parallax-factor alignment chart. PNW Old Series Research Notes No. 183, p. 1-4