Each 30-degree sign is divided into nine equal 3°20′ parts. The resulting D9 sign follows a fixed sequence: movable signs begin from themselves, fixed signs from the ninth, and dual signs from the fifth.
Navamsa is read alongside the birth chart, not in place of it. It adds a finer traditional layer, but a reliable reading still begins with an accurate birth time, ascendant and the visible planetary placements of the main chart.