Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c12.s7.6

v2.c12.s7.6

Palabhā is the name given to the length of the shadow cast by the twelve-angula gnomon at any place on the equinoctial day. Palabhā forms the base, gnomon the perpendicular and the line joining the extremities of the gnomon and the shadow, the ‘akṣa-karṇa’ (hypotenuse). The area bounded by this right angled triangle is termed ‘akṣa-kṣetra’. This region of ‘akṣa-kṣetra’ has much importance in our astronomy. At many places, the measures of different items are calculated by drawing another figure similar to this ‘akṣa-kṣetra’; and the Adhikāra on three problems devotes much space to problems associated with such figures.