Underwater positioning and navigation system and method based on DGPS

The invention discloses an underwater positioning and navigation system and method based on the DGPS. The system is composed of GNSS satellites, at least four DGPS buoys and at least one underwater positioning and navigation receiver. The buoys receive GPS signals and are in wireless communication with one another so that DGPS positioning can be achieved. The buoys broadcast navigation signals to water. Frequency spread can be conducted on the navigation signals through pseudorandom frequency spread codes, wherein the frequency spread codes play a role of ranging codes at the same time. The underwater positioning and navigation receivers do not need to transmit signals outwards. The underwater positioning and navigation receivers resolve the positions of the underwater positioning and navigation receivers in the earth coordinates and the accurate positions of the underwater positioning and navigation receivers relative to a base station by means of the received navigation signals of the buoys. Time synchronization of the underwater positioning and navigation receivers and the UTC is achieved. Multiple underwater positioning and navigation receivers can be arranged in the system to simultaneously receive the navigation signals, and the number of the underwater positioning and navigation receivers is not limited. The underwater positioning and navigation system and method can be applied to the underwater exploration field, the under water construction field, the underwater security and protection field, the underwater navigation field and other fields.