The Beijing 54 coordinate system and the Xi'an 80 coordinate system are actually a transformation of ellipsoidal parameters. As such transformations, the transformations in the same ellipsoid are strict, and the transformations between different ellipsoids are not strict. Therefore, there is no set of conversion parameters that can be used nationwide and will be different in each place, because they are two different ellipsoid benchmarks. Then, in general, the coordinate transformation between two ellipsoids is more strictly using a sevenparameter Bursa model, namely X translation, Y translation, Z translation, X rotation (WX), Y rotation (WY), and Z rotation ( WY), scale change (DM). If seven parameters are obtained, it is necessary to provide more than three common point coordinate pairs in one area (ie x, y, z in Beijing 54 coordinates and x, y, z in Xi'an 80 coordinate systems). If the area range is not large, the most The distance between the far points is not more than 30km (empirical value). This can be done with three parameters, namely X translation, Y translation, Z translation, and X rotation, Y rotation, Z rotation, and scale change surface DM are regarded as 0.
method:
Step 1: Find the three common point coordinate pairs (ie x, y, z in Beijing 54 coordinates and x, y, z in Xi'an 80 coordinates) from the local surveying and mapping bureau (or elsewhere);
Step 2: Talk about the conversion of the coordinates of the three points in radians. (Menu: Projection TransformationEnter a single point projection transformation, calculate the radian values of these three points and record them);
The third step: find the common point operation coefficient (menu: projection transformationcoordinate system transformation). If the conversion coefficient is obtained, record it;
Step 4: Edit the coordinate conversion coefficients (menu: projection conversionedit coordinate conversion coefficients), and finally perform the projection conversion. Enter 80 coordinate system parameters for "current projection" and 54 coordinate system parameters for "target projection". When converting, the system will automatically call the edited coordinate conversion coefficient.
First set the working path of the MAPGIS platform to the “… .. \ Beijing 54 to Xi'an 80” folder.
Below we explain the conversion method and steps of "Beijing 54 coordinate system" to "Xi'an 80 coordinate system".
I. data description
The conversion between Beijing 54 coordinate system and Xi'an 80 coordinate system is actually a conversion between two different ellipsoidal parameters. Generally speaking, the sevenparameter bursa model is used more strictly, namely X translation, Y translation, Z translation , X rotation (WX), Y rotation (WY), Z rotation (WY), scale change (DM). If there are seven parameters, you need to provide more than 3 common point coordinate pairs in one area (that is, x, y, z in Beijing 54 coordinates and x, y, z in Xi'an 80 coordinate systems), which can be obtained from the local surveying and mapping bureau.
Second, the Beijing 54 coordinate system "to" Xi'an 80 coordinate system "operation steps
Start the "Projection Transform Module" and click the "Open File" command under the "File" menu to present the demo data "Demo Data_Beijing 54.WT", "Demo Data_Beijing 54.WL", "Demo Data_Beijing 54. WP "opens:
1. Click "Projection Transformation", click "S Coordinate System Transformation" and "Order", the system will pop up the "Transformation Coordinate Value" dialog box:
In the "Input" column, the coordinate system is set to "Beijing 54 Coordinate System" and the unit is set to "line unitmeter";
In the "Output" column, the coordinate system is set to "Xi'an 80 coordinate system", and the unit is set to "line unitmeter";
In the "Conversion method" column, click the "Common point operation to find the coefficient" item;
In the "Input" column, enter (x, y, z) of the next common point in the Beijing 54 coordinate system, as shown in Figure 2;
In the "Output" column, enter (x, y, z) of the corresponding common point in the Xi'an 80 coordinate system, as shown in Figure 2;
In the lower right corner of the window, click the "Enter common point" button, and the number on the right becomes 1, indicating that a common point pair has been entered, as shown in Figure 2;
In the same way, input another 2 common point pairs;
In the "Conversion Method" column, click the "Sevenparameter Bursa Model" item to activate the conversion coefficient item on the right;
Click the "Find Conversion Coefficient" command under the "Find Conversion Coefficient" menu. The system automatically calculates 7 parameters based on the input of the 3 common points to the coordinates and records them.
Then click the "OK" button;
2. Click the "Edit Coordinate Transformation Parameters" command under the "Projection Transformation" menu, and the "Different Geographic Coordinate System Transformation Parameter Settings" dialog box pops up:
In the "Coordinate System Options" column, set the parameters as follows:
Source coordinate system: Beijing 54 coordinate system;
Destination coordinate system: Xi'an 80 coordinate system;
Conversion method: Sevenparameter Bursa model;
Unit of length: meters;
Angle unit: radian;
Then click the "Add Item" button, the conversion relationship is listed in the "Transformation between different ellipsoids" list on the left side of the window;

In the "Parameter Setting" column at the bottom of the window, enter the seven parameters obtained in the previous step into the corresponding text boxes, as shown in Figure 4;
Click the "Modify Item" button, enter the conversion relationship, and click the "OK" button;
The next step is the operation of file projection.
3. Click the "MAPGIS Projection Conversion / Select Conversion Line File" command under the "Projection Conversion" menu, the "Select File" dialog box pops up, select the file to be converted "Demo Data_Beijing 54.WL" and click "OK "Button;
4. Set the Tic point of the file. Two methods are provided under the "Projection Transform" module: manual setting and copying between files, which will not be described in detail here;
5. Click the "Edit Current Projection Parameters" command under the "Projection Conversion" menu, and the "Input Projection Parameters" dialog box pops up, as shown in Figure 6. Set the map parameters according to the actual situation of the data, as follows:
Coordinate system type: Geodetic coordinate system
Ellipsoidal parameters: Beijing 54
Projection type: GaussKruger projection
Scale denominator: 1
Coordinate unit: meter
Longitude of projection center point (DMS): 1230000
Then click the "OK" button;
6. Click the "Set Conversion Parameters" command under the "Projection Conversion" menu. The "Input Projection Parameters" dialog box pops up. The converted parameters are set to:
Coordinate system type: Geodetic coordinate system
Ellipsoidal parameters: Xi'an 80 (note the transformation of ellipsoidal parameters)
Projection type: GaussKruger projection
Scale denominator: 1
Coordinate unit: meter
Projection center point longitude (DMS): 1230000 (note that the central meridian before and after remains the same)
7. Click the "Perform Projection Transformation" command under the "Projection Transformation" menu. The "Input shift value after transformation" dialog box pops up. Click the "Start Conversion" button, and the system starts to convert the line file according to the set parameters:
With the same operation steps and parameter settings, the "demo data_Beijing 54.WL" and "demo data_Beijing 54.WP" files are projected and converted;
8. Rightclick and select the "Reset" command. The "Select File Name" dialog box pops up. You can see that the system has generated three new files: "NEWLIN.WL", "NEWPNT.WT", and "NEWPNT. WP ", select these three files in turn, and click the" OK "button.
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