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Original link: https://blog.csdn.net/m0_37251750/article/details/99941276
Reference thanks: WeChat public account GIS foreword
Question : Are the latitude and longitude coordinates of the same point the same in different geographic coordinate systems?
Answer : At present, the Ministry of Land and Resources requires the registration of mineral rights to adopt the Xi'an 80 coordinate system. Previously, the Beijing 54 coordinate system was used. I thought that the latitude and longitude of the same point in the two coordinate systems should be the same. The only difference is that the converted rectangular coordinates are different. Later, the coordinates of a known point in two different coordinate systems provided by the Ministry of Land and Resources can be determined, and the latitude and longitude of the same point under the two geographic coordinate systems are quite different . And there is no better conversion software. The best solution is to use 7-parameter and 3-parameter conversion .
1. Data parameter considerations
1. The surveying and mapping data we use, such as:
X——2835697.754 X is the latitude (7 digits)
Y——613544.641 Y is the longitude (6 digits)
if:
X——2835697.754 X is the latitude (7 digits)
Y——36613544.641 Y is the longitude with the number 36 (8 digits)
2. The X and Y in ArcGIS should be opposite to the X and Y of the surveying and mapping data, so you must pay attention when generating the point data.
3. The X and Y in the COORD software are the same as the X and Y of the surveying and mapping data.
4. The coordinates of the seven parameters in ArcGIS: the unit of the translation parameter is meters, the unit of the rotation parameter is seconds, and the unit of the scale parameter is millions.
5. In the COORD software, the coordinates of the seven parameters: the translation parameter unit is meter, and the rotation parameter unit is radians.
6. Therefore, in order to import the seven parameters in COORD into ArcGIS, the seven-parameter coordinate conversion must be performed.
2. Explanation of the conversion steps from Xi'an 80 coordinates to national 2000 coordinates
1. Open the COORD software
There is no national 2000 coordinate system ellipsoid in the COORD software, and CGCS2000 needs to be added to the ellipsoid management. 
The long radius and flatness are consistent with the relevant parameters in ArcGIS.
2. Setting-map projection-setting the central meridian. In this example, the central meridian is 102: 00: 00.000000 
3. Setting-calculation of seven parameters 
Select the source coordinate ellipsoid: country 80. Target coordinate ellipsoid: cgcs2000 (the ellipsoid added above).
The source coordinates use latitude and longitude format, and the target coordinates use plane coordinates without numbers.
When there is no elevation information, you can use the coordinate calculation parameters without elevation values.
Xi'an 80 is a reference coordinate system, and the country 2000 is a geocentric coordinate system. The transformation between the two different types of coordinate systems requires the use of Bursa seven parameters.
Choose model: Bursa, calculate, get seven parameters.
Note here: the unit of the translation parameter is meter, and the unit of the rotation parameter is radians. Cannot be used directly in arcgis.
4. The calculated seven parameters are converted into units in the excel sheet.
The unit of the rotation parameter is radians, converted to seconds:
2π= 360°，1rad=57.32°
So 1 radian=57.32*3600 seconds
Scale*1000000=ArcGIS scale 
The seven parameters after unit conversion can be directly used in ArcGIS.
5. Open ArcGIS, ArcToolbox-Data Management Tools-Projections and Transformations-Raster-createCustom Geographic Transformation 
There are two models of seven parameters in ArcGIS, POSITION_VECTOR and COORDINATE_FRAME. POSITION_VECTOR angle parameter is negative counterclockwise, and COORDINATE_FRAME angle parameter rotates counterclockwise Is positive.
6. ArcToolbox-DataManagement Tools-Projections and Transformations-Feature-Project 
will get the country 2000 coordinates after seven-parameter conversion.
The COORD software can be downloaded online.