The Rashi chart, D-1, is the first and foundational of the sixteen divisional charts (shodashavarga) of jyotisha. In Vedic astrology a single birth moment is analysed not through one chart but through a set of harmonic subdivisions, each magnifying a particular area of life. The Rashi is the base chart, dividing each sign into a single whole, and it signifies the body, the overall shape of life, and the physical self. Every other varga is derived from it by a further division of each sign. An astrologer reads the D-1 first for the broad structure of the nativity, then turns to the finer charts for detail. These are the interpretive conventions of the tradition; the divisional charts are a mathematical technique for extracting multiple readings from the same set of planetary longitudes.
Brihat Parashara Hora Shastra also supplies the arithmetic for weighing all sixteen charts together, the vimshopaka bala, a composite strength score out of twenty points built by giving each varga a fixed weight and summing a planet's dignity across the set; the Rashi, the Navamsha and the Shashtiamsha carry the three highest weights in the full sixteen-chart scheme, reflecting the same emphasis on D-1, D-9 and D-60 that shows up throughout the tradition's own commentary. Parashara gives a rough reading of the resulting total: a score under five promises little of the planet's significations, five to ten gives some effect, ten to fifteen a moderate one, and above fifteen the planet is held to deliver its full promised results.