Everyone knew that there are 12 signs in the entire zodiac belt. These 12 zodiac signs are represented in paper as a square with 12 boxes in southern India as given below,
The zodiac belt is circular in space. Some identify it as moving and some scientists as it is fixed. Each and every sign is nothing but a constellation (group of stars). So, there are 12 constellation made up of numerous stars. Imagine a circle, a circle comprises of 360° degree,
Each point represents 1 Zodiac sign or Rasi(in Tamil) along the 360° degree path.Hence, 360°/12 = 30° for each sign. This is very important, everyone should know this.
Representing it in a circle is not so easy for all except for mathematicians that is why only person who are scientists, philosophers and mathematicians used to learn astrology and research it as a part of their main subjects in olden days.
Western Astrology system still uses circular charts to explain, while
South Indian people including Sri Lanka, uses Square Chart.
North Indian astrologers uses Diamond chart.
It is only for the ease of understanding. Diagrams or charts represent the celestial map very well in paper.