The Rama Yantra is used to observe the position of any celestial object by aligning an object in the sky with both the top of the central pillar, and the point on the floor or wall that completes the alignment. In the daytime, the sun’s position is directly observed at the point where the shadow of the top of the pillar falls on the floor or wall. At night, an observer aligns the star or planet with the top of the pillar and interpolates the point on floor or wall that completes the alignment through the use of a sighting guide.
The floor is constructed as a raised platform at chest height, and is arranged in multiple sectors with open spaces between them. This provides a space for the observer to move about and comfortably sight upwards from the inscribed surface. The instrument is most accurate near the intersection of floor and wall, corresponding to an altitude of 45 degrees. Here, the markings are at their widest spacing, and give an accuracy of +/- 1’ of arc. For altitude readings greater than 45 degrees, the accuracy diminishes, and diminishes to +/- 1 degree near the base of the pillar.