Shanku Yantra

Shanku Yantra

A vertical gnomon (Shanku) is fixed at the centre of the circular platform having a horizontal shape. The seven lines drawn according to the shadow of the gnomon indicate the twelve zodiac signs. Among these lines, the 22nd December makes the shortest day, the 21st March and the 23rd September make the days and nights equal, and the 22nd June makes the longest day of the year. With the help of the shadow of the gnomon the angle of elevation and zenith distance of the sun can determined. The Altitude of Ujjain is determined by the mid-day shadow of Shanku Ynatra when the days and nights have equal length.