The South Australian General Armed Forces is located between the east of Guangdong and southern Fujian. It is a military location in the southeastern coast of Nan'ao Island. It is the name of the Ming and Qing Dynasties and the headquarters of the South Australian General. Like the South Armed Forces, the regional zoning function is the Tropic of Cancer. The two are the ancient military and the dividing line of the temperature band. The Qinghai Bay Tropic of Cancer marking tower, the Tropic of Cancer is the dividing line between the north temperate zone and the climatic zone on the earth, that is, the weft coil of 23°26' north latitude. The Tropic of Cancer marker tower is a landmark building that passes through the geography of the Tropic of Cancer. The Tropic of Cancer is an imaginary line that is invisible. The establishment of the sign tower allows people to visually see the objective entities of the Tropic of Cancer and feel the existence of this latitude. It is of great significance to the scientific research of astronomy, geography, soil, biology and climate.