What is the conversion process of coordinate system in GPS measurement?

The following is the related content of coordinate system transformation in GPS survey brought by Zhong Da Consulting for your reference.

GPS has been widely used in the field of measurement. This paper introduces the process of converting WGS-84 coordinates collected by GPS into coordinates needed by engineering.

I. Overview of Global Positioning System and its applications

GPS (GlobalPositioningSystem) is a satellite navigation and positioning system developed by the United States in 1970s, which lasted for 20 years and cost 20 billion dollars. Completed on 1994. As a new generation of satellite navigation and positioning system, after more than 20 years of development, it has become a widely used system in aviation, aerospace, military, transportation, resource exploration, communication meteorology and other fields. Surveying and mapping departments in China have also used GPS for nearly ten years. At first, it was mainly used for high-precision geodetic survey and control survey, and various types and grades of survey control networks were established. Now, in addition to continuing to play an important role in these fields, it has been fully applied in other aspects of surveying, such as various engineering surveys, deformation observation, aerial photogrammetry, marine surveys and geographic data collection in geographic information systems. GPS measurement accuracy is high; Simple operation, small size and easy to carry; All-weather operation; There is no need for intervisibility between observation points; The measurement results are unified in WGS84 coordinates, and the information is automatically received and stored, which reduces the complicated intermediate processing links and has high efficiency and won the trust of the majority of surveying and mapping workers.

Second, the coordinate system commonly used in GPS measurement

1.WGS-84 coordinate system

WGS-84 coordinate system is the coordinate system adopted by GPS at present, and the ephemeris parameters released by GPS are based on this coordinate system. The full name of WGS-84 coordinate system is WorldGeodicalSystem-84 (World Geodetic Coordinate System -84), which is a geocentric stereo coordinate system. The WGS-84 coordinate system was established by the Cartographic Bureau of the US Department of Defense. 1987 replaced the coordinate system used by GPS at that time-WGS-72 coordinate system and became the coordinate system used by GPS. The coordinate origin of WGS-84 coordinate system is located in the center of the earth, the Z axis points to the agreed earth pole defined by BIH 1984.0, the X axis points to the intersection of the meridian plane at the starting point of BIH 1984.0 and the equator, and the Y axis, X axis and Z axis form a right-handed system. The parameters of ellipsoid are: a = 6375438+037mf = 1/298.

2. 1954 Beijing coordinate system

Beijing coordinate system (1954) is a widely used geodetic coordinate system and a reference coordinate system in China. This coordinate system is derived from the 1942 Pulkov coordinate system adopted by the former Soviet Union. The reference ellipsoid used in this coordinate system is Krasovsky ellipsoid, and the parameters of this ellipsoid are: a=6378245mf= 1/298.3. The plane coordinate positions on topographic maps of our country are all calculated according to this data.

3. Local coordinate system (any independent coordinate system)

In our survey process, we often encounter some coordinate systems, such as a city coordinate system, a city building coordinate system, a port coordinate system and so on. , or an independent coordinate system temporarily established by ourselves for the convenience of measurement.

Third, the transformation of coordinate system

In engineering application, the data collected by GPS satellite positioning system is WGS-84 coordinate system, but at present our measurement results are generally based on 1954 Beijing coordinate system or local (arbitrary) independent coordinate system. Therefore, it is necessary to convert WGS-84 coordinate system into BJ-54 coordinate system or local (arbitrary) independent coordinate system.

At present, Bursa formula (seven-parameter method) is generally used to complete the transformation from WGS-84 coordinate system to Beijing 54 coordinate system and get Beijing 54 coordinate data.

xbj 54 = xwgs 84 kxwgs 84δxywgs 84ξZ "/ρ"-zwgs 84ξY "/ρ"

ybj 54 = ywgs 84 kywgs 84δY-xwgs 84ξZ "/ρ" zwgs 84ξX "/ρ"

zbj 54 = zwgs 84 kzwgs 84δzxwgs 84ξY "/ρ"-zwgs 84ξX "/ρ"

Fourthly, the transformation of coordinate system.

There are many different forms of coordinates in the same coordinate system, and one form is actually a coordinate system. Such as space rectangular coordinate system (x, y, z), geodetic coordinate system (b, l), plane rectangular coordinate system (x, y) and so on. Through the transformation of coordinate system, the spatial rectangular coordinates in BJ54 coordinate system are obtained, and various coordinate systems need to be transformed in BJ54 coordinate system until the coordinates needed by the project are obtained.

1. Convert the space rectangular coordinate system into geodetic coordinate system, and get geodetic coordinate (b, l):

L = arctangent (Y/X)

B=arctan{(ZNe2sinB)/(X2Y2)0.5}

H=(X2Y2)0.5sinB-N

Using the above formula, geodetic coordinates (b, l) are obtained by iterative method.

2. Convert the geodetic coordinate system into Gaussian coordinate system to obtain Gaussian coordinate (x, y).

According to the method of Gaussian projection, the Gaussian coordinates are obtained, x = f 1 (b, l), y = F2 (b, l).

3. Convert the Gaussian coordinate system into any independent coordinate system to obtain independent coordinates (x', y').

In small-scale measurement, we can regard the ground as a plane and simply rotate and translate the Gaussian coordinates to the coordinates (x', y') of the coordinate system used in engineering.

x'=xcosαysinα

y’= ycosα-xsinα

Verb (abbreviation of verb) abstract

Because of the advantages of GPS measurement, GPS positioning technology has basically replaced the conventional measurement method and become the main technical means. There are many conversion software, and different types of GPS data processing support software (including the function of how to convert WGS-84 measured by GPS into coordinates needed in engineering) are the same. As long as you understand the conversion process from WGS-84 to independent coordinate system, you can easily use the software and even write it yourself.

For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd