Sailing Glossary - Term Grid nephoscope

A direct-vision nephoscope constructed in the following manner: A grid-work of bars is mounted horizontally on the end of a vertical column and made free to rotate about the vertical axis. The observer rotates the grid and adjusts his or her position until some feature of the cloud appears to move along the major axis of the grid. The azimuth angle at which the grid is set is taken as the direction of cloud motion.