GPS technology in the construction of the airport

　3, GPS coordinate system

Usually two types of GPS coordinate system, one fixed in space coordinate system, the other is associated with the Earth fixed bulk coordinate system, also known as ground fixed coordinate system, such as commonly used in the mapping field WGS-84 (ie Geodical System-84 World Geodetic System -84), 1954, Beijing coordinate system (referred to as P54) and the geodetic coordinate system in Xi'an in 1980 (referred to as C80), in actual use need to convert between coordinate systems coordinate system transformation parameters , find the coordinates of the coordinate system used. This expression is more conducive to the location of ground control points and processing of GPS observation results.

4, GPS technology features

GPS is a versatile, multi-model, multi-mode space positioning technology, has the following characteristics:

4.1 High accuracy dual-frequency GPS receiver Baseline general accuracy of 5mm +1 ppm, while the nominal accuracy for the infrared instrument 5mm +5 ppm, significantly higher than those observed in the accuracy of conventional measurement methods, GPS baseline vector relative accuracy of typically 10 - between 5 ~ 10-9.

4.2 The choice of site flexible, low-cost GPS measurements for each pass is between stations, as well as control network geometry were not strict requirements, making the choice of site is more flexible and convenient, low cost of its operations, but also greatly reduce the distribution network costs. According to an actual measurement, GPS technology than the conventional geodetic save at least 70% of the foreign business costs.

4.3 global operations around the clock at any place, any time, any weather conditions were continuously observed GPS can greatly facilitate the measurement operations.

4.4 GPS laid by observing speed control network in which each station is generally on the observation time is about 30 ~ 40min, the rapid static positioning m