Also called the Birthplace House System. A system of house division developed by Dr. Walter Koch and based on dividing the quarters of the chart formed by the Ascendant and Midheaven axes into three equal time segments. For cusps above the Horizon, the semidiurnal arc (along a small circle) of the Rising Degree (Ascendant) is trisected; then, altitude circles (small circles parallel to the Horizon) are constructed through the points of trisection; finally, the cusps are determined by the intersections of these altitude circles with the Ecliptic. For cusps below the Horizon, the seminocturnal arc is used. The MC and ASC, are the same, respectively, as the cusps of the 10th and 1st houses.