The Placidus house system is the most popular Western astrology house division method, calculating houses based on time rather than space.
Developed in the 17th century, the Placidus system divides houses based on the time it takes for each degree of the ecliptic to rise from the horizon to the midheaven. This creates unequal house sizes that vary with latitude. Placidus works well for most locations but becomes distorted at extreme latitudes (above 66°) where some signs never rise. TriAstra uses Porphyry as a fallback for polar regions.
TriAstra uses Placidus as the default house system for Western charts, automatically switching to Porphyry for births above 66° latitude to ensure accurate calculations.
The house system affects which houses your planets occupy. Placidus is the most widely used system, making it easier to compare your chart with popular astrology resources.
Understanding Placidus House System is just the beginning. See how it manifests in your unique birth chart with TriAstra's triple-system analysis.
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