A house system is a calculation method used to organize an astrological chart into twelve houses. Different house systems use different mathematical or geometrical approaches to establish the house cusps, so the boundaries of individual houses can vary from one system to another. As a result, the same accurately calculated planetary position may sometimes fall into a different house depending on the house system being used. This does not eliminate the need for an accurate birth time and birth location. Those remain essential inputs for house systems that depend on the chart’s orientation to the time and place of birth. Examples include the Placidus, Whole Sign, Equal House, Koch, Regiomontanus, and Campanus systems.