Whole Sign
Hellenistic astrologers (~1st century BCE)
oldest system · each house = one sign · Hindu astrology default · Project Hindsight revival
How it divides the sky
The simplest system: the entire ascending sign is the 1st house, the entire next sign is the 2nd house, etc. If Asc is at 22° Gemini, the entire 1st house is Gemini 0°-30°. In this system the Ascendant is not a "house cusp" but a "degree within the sign." Advantage: latitude-independent, consistent worldwide. Not quadrant-based.
When to use it
The default if you work with Hellenistic astrology. Hindu (Vedic) astrology already uses it. Since the 90s, Project Hindsight revived it in the West — Demetra George, Chris Brennan are main advocates. If you were born near the poles, the only system that works correctly.
History
Was the default system of the Hellenistic world from ~1st century BCE to ~7th century CE. Almost all ancient texts (Vettius Valens, Ptolemy) use it. Forgotten after the Arabic transformation, rediscovered in the 1990s.