In addition, some modern astrologers who follow the X=Y=Z or Planet=Sign=House doctrine, which was first taught by Alan Leo in the early part of the 20th century, believe that certain houses are also ruled by—or have an affinity with—the planet which rules the corresponding zodiacal sign. For instance, Mars is ruler of the 1st house because it rules Aries, the first sign; Mercury rules (or has an affinity with) the 3rd house because it rules Gemini, the 3rd sign; etc.[51]
This concept is sometimes referred to as "natural rulership", as opposed to the former which is known as "accidental rulership".
Placidus
The Pacidus house system divides the phases of planetary and star movement above and below the horizon into equal-sized parts. A planet on the cusp of the twelfth house, for example, has already passed 1/6 of its so-called diurnal arc, a planet on the eleventh house cusp 2/6, a planet on the MC 3/6 or half of its diurnal arc, etc. The houses below the horizon divide the so-called 'nocturnal arc' of the stars and planets.
So, the Placidus system divides celestial movements and is consequently considered a time-oriented system.
For mathematical reasons, Placidus houses cannot be calculated for regions beyond the polar circles.
The Placidus house system is named after the Italian monk and mathematician Placidus de Titis (1603-1668), but was invented by the astronomer and mathematician Giovanni Antonio Magini (1555-1617).
More information can be found in the Astro Wiki
Koch
The Koch house system (also called "house system of the birth place") is defined by horizon lines at different times on the day of birth. We calculate the timespan that the MC zodiac degree has spent above the horizon since its rising. The cusp of the twelfth house is where the Ascendant was when 1/3 of this time had passed, the eleventh house cusp is where the Ascendant was when 2/3 of that time had passed. The cusps of houses 9 and 8 can be explained as Descendants for 1/3 and 2/3 respectively of this time span after birth.
Therefore, the Koch house system assigns special significance to the MC-IC axis, because the measure of the division is predefined by the diurnal arc of the zodiacal degree of the MC at birth. Like Placidus, the Koch system divides celestial movements and is therefore considered a time oriented system.
For mathematical reasons, Koch houses cannot be calculated for regions beyond the polar circles.
The house system is named after the German astrologer Walter Koch (1895-1970) but was actually invented by Fiedrich Zanzinger (1913-1967) and Heinz Specht (1925-).
More information can be found in the Astro Wiki
Equal
The equal house system defines the Ascendant as the cusp of the first house. Each house has the same size ("equal") of exactly 30°. The 10th house cusp therefore does not coincide with the MC but is square to the Ascendant and consequently the highest point of the zodiac above the horizon.
The equal house system has been in use since the time of antiquity.
More information can be found in the Astro Wiki
Equal (MC)
This house system places the MC exactly on the cusp of the 10th house. Each house has the same size ("equal") of exactly 30°. The Ascendant does not usually coincide with the cusp of the 1st house.
More information can be found in the Astro Wiki
Whole Sign Houses
The Whole Sign house system considers the whole sign of the zodiac that contains the Ascendant as the first house. The following zodiac sign is the second house and so on. Here, houses are always complete zodiac signs. The Whole Sign houses belong to the group of equal ("same size") houses.
The Whole Sign house system has been in use since antiquity and is currently especially popular in Indian siderean astrology.
Whole sign houses, 1. house = Aries
The first house begins at the cusp of Aries, all houses have the same size ("equal"), and each house covers a whole zodiac sign.
