Geographical Information Technology Global Positioning System

The Global Positioning System (Globle Positioning System) is a technology that combines the development of satellites and communications, using navigation satellites for timing and ranging. The Global Positioning Satellite System (GPS for short) was developed by the United States starting in the 1970s. It took more than 20 years and cost 20 billion US dollars, and was fully completed in 1994. A new generation satellite navigation and positioning system with all-round real-time three-dimensional navigation and positioning capabilities on land, sea and air. After nearly ten years of use by my country's surveying and mapping departments, it has been shown that the global satellite positioning system has been successfully used in geodetic surveying, engineering surveying, aerial photography, vehicle navigation and control, and crustal movement with its characteristics of all-weather, high precision, automation, and high efficiency. Surveying, engineering deformation measurement, resource survey, geodynamics and other disciplines have achieved good economic and social benefits.

The GPS satellite constellation consists of 21 working satellites and 3 in-orbit backup satellites. Distributed in six orbital planes. There are four GPS satellites above the ground at any place and at any time.

The GPS global satellite positioning system consists of three parts: the space part-GPS constellation (GPS constellation is a constellation composed of 24 satellites, of which 21 are working satellites and 3 are backup satellites); ground control Part—Ground monitoring system; User equipment part—GPS signal receiver. The user equipment part is the GPS signal receiver. Its main function is to capture the satellites to be measured selected according to a certain satellite cut-off angle and track the movement of these satellites. When the receiver captures the tracked satellite signal, it can measure the pseudo-distance and distance change rate from the receiving antenna to the satellite, and demodulate satellite orbit parameters and other data. Based on these data, the microprocessor computer in the receiver can perform positioning calculation according to the positioning solution method, and calculate the longitude, latitude, altitude, speed, time and other information of the user's geographical location. The receiver hardware, on-board software and GPS data post-processing software package constitute a complete GPS user equipment. The structure of the GPS receiver is divided into two parts: the antenna unit and the receiving unit. Receivers generally use two types of DC power supplies, internal and external. The purpose of setting up the internal power supply is to maintain continuous observation when replacing the external power supply. The internal battery is automatically charged when using an external power source. After shutting down, the internal battery powers the RAM memory to prevent data loss. Currently, various types of receivers are getting smaller and lighter, making them easier to use for field observations.

The Global Positioning System has six major characteristics: first, all-weather, not affected by any weather; second, global coverage (up to 98%); third, high-precision seven-dimensional fixed-point speed and timing; Fourth, it is fast, time-saving and efficient; fifth, it is widely used and multi-functional; sixth, it can be moved and positioned.

my country’s satellite navigation system, Beidou-1, was successfully developed. It plays an important role in fisheries and other aspects.