The Universal System of Astronomy, Part Two

Commentary on the Siddhanta Samrat original: si. sā. vi., likely abbreviating Siddhānta-Samrāṭ-Vivaraṇa

...the measured time-units nāḍī; a unit of time equivalent to 24 minutes, then from the sine-axis jīvākṣa; the axis used for calculating trigonometric sines and the sequence of intervals. In the center of the circle, the half-angle original: koṇārddhaḥ is formed at the sun's position. That line also represents the movement of the center's radius, whether in retrograde vakrī; the apparent backward motion of a planet or direct motion upon the horizon kṣitija; the circle where the earth meets the sky.

The lines originating from the center are designated as the Earth bhūmi; the horizontal base line of the instrument. Within the diagonals, the Sky-Mountain original: ākāśaparvata; likely referring to the vertical zenith point or the 90-degree marker on the quadrant is divided into ninety equal parts original: navatirvibhāgāḥ samāḥ; these represent the 90 degrees of altitude from horizon to zenith.

From the Sky the zenith to the Mountain of Duration original: sthitigeya-parvata, there are ten equal ghatikas approximately 4 hours of time. Starting from the Earth-line and extending to the rim nemi; the outer edge of the quadrant, the Line of Cancer karkajīrekhā; the line representing the Sun's position at the Summer Solstice is shaped like the Sky-line.

In this manner, there are thirty-five sines jīvā; chords used in Indian trigonometry placed at equal intervals. The space between these sines is measured as one digit aṅgula; a traditional unit of length roughly equal to the width of a finger. In this region, one minute of arc kalā; 1/60th of a degree corresponds to the sine. From the center, the divisions of the latitude palāṃśa; the degrees of latitude of the observer's location are to be understood in the sky-divisions. These are to be known through both the regular and inverse sequences. Calculation of Rama

From the horizon-shadow original: kṣitija-chāyā, the eighteen interval lines are marked with the total number of digits, measuring twenty-seven and a half digits original: sārdhasaptaviṃśatyaṅgulā. From the top of that, where the shadow falls, a cord is extended from the center to the circumference. From the point where it intersects the rim, following its own path to the Mountain of Position the fixed marker, there are six divisions original: ṣaḍtōṃśāḥ. At the corner of the Sky-Mountain, there are likewise six divisions or parts in the sequence.