In geometry, what is "projection" and what is its application?

Is a term in geometry, and projective geometry studies the projective properties of figures, that is, their invariant properties after projective transformation. Once, it was also called projective geometry. In classical geometry, projective geometry is in a special position, through which other geometries can be linked.

Some contents of projective geometry were discovered in 2000 BC. Based on the needs of cartography and architecture, ancient Greek geometricians began to study perspective, namely projection and silhouette. But it was not until the19th century that an independent system was formed and became more complete.

1822, French mathematician Poncelet published the first systematic work on projective geometry. He was the first mathematician to realize that projective geometry is a new branch of mathematics.

Projective geometry is widely used in aviation, surveying, drawing and photography.