In geometry, a protractor is a circular or semicircular measuring instrument  (made of transparent plastic or glass) used for measuring angles. Structurally, a full circle protractor is a Compass, and a half circle protractor is half of a compass.

The 360° protractor (a full circle protractor) is a compass depicting the celestial hemisphere. This means that the 360° protractor is a throne and the centre zero of the protractor is the observer (the king) on the throne.

As a celestial sphere, the protractor is made up of circles of latitude and circles of longitude. The circles of latitude are the four concentric circles of the 360° compass, the circles of latitude are the eight winds or eight directions of the compass, and the celestial equator is the circumference of the protractor.

The four concentric circles or four circles of latitude or four parallels are products of the transverse section of the celestial sphere, and the eight lines of longitude are products of the longitudinal section of the celestial sphere.

Celestial hemisphere is a celestial sphere because there is nothing on the other side of the globe. What this means is that the half where the observer is is the physical and the other half is the metaphysical. The metaphysical side is the throne of God and the centre of the invisible half is God on his throne. In other words, man is a king on a throne like God is a King on his throne.

Geometry is the language of the metaphysical. In other words, heaven or paradise is not spoken in words, but in geometry. Since geometry is a subject, God and heaven are learnt in school. The protractor is heaven itself; using it to measure angles is an act of mapping out heaven.

Saint Peter's Square in the Vatican City is a giant protractor depicting the celestial sphere and the first eight major Cardinal directions.

Wondering why Catholic Bishops from all parts of the world are called Cardinals? The reason is that the Bishops are representatives of the different directions of the compass. This means that the compass is the kingdom.

The four cardinal points are the four winds, which means that the gathering of the Cardinals is the gathering of the four winds.

In Chinese Cosmology, the protractor is Bagua. It is the Compass Rose crested on the floor of Dome of the Chain.