Precise projection conversion of three or seven parameters in ArcGIS Desktop

The projection conversion method defined in ArcGIS is often unsuitable for projects with high spatial information requirements and has obvious deviations. In the preliminary data preparation of the project, a more precise projection conversion of three or seven parameters is required. The following describes two methods to perform this conversion in ArcGIS Desktop.

Method 1: perform dynamic conversion (on the fly) In ArcMap)
Assume that the original projection coordinate system is the xian80 coordinate system. In this example, projected coordinate systems \ Gauss Kruger \ Xian 1980 \ Xian 1980 GK zone 20 projection is selected as the preset system, and the central longitude line is 117 degrees, convert to Beijing 1954 \ Beijing 1954 GK zone 20n.

After the layer is loaded In ArcMap, the view-data frame Properties dialog box is displayed, showing that the current projection coordinate system is Xian 1980 GK zone 20, select Beijing 1954 GK zone 20n in the following select coordinate system box, and there is a button on the right for transformations...

Click to open a projection conversion dialog box. The convert from and into dialog box shows the coordinate system from which we want to convert to which coordinate system.

On the Right of the using drop-down box below, click New ..., create a new projection conversion formula. In the method drop-down box, you can select a series of conversion methods, some of which are three parameters, some of which are seven parameters, and then enter each conversion parameter in the parameter table.

After the input is complete, click OK to return to the previous projection conversion dialog box, and then click OK to complete the dynamic projection conversion for the current map. At this time, the projection of the layer file itself has not been converted. to convert the projection of the layer file itself, use data export. When exporting, select the projection as the projection of the current map.

Method 2: For many layers that require projection conversion, this manual method is cumbersome and requires parameters to be set each time. The projection conversion formula can be defined only once, and can be referenced in the subsequent conversion. This method requires operations in arctools. The create M geographic transformation command is available under data management tools \ projections and tranformations.

Open this command and select the projection of input and output. It can be either built-in or set by the system. Select the conversion method, which is similar to the one described in method 1, you can select three or seven parameters, and then enter each parameter. By specifying a name for this projection conversion formula, you can reference this formula directly in future operations without entering parameters again. Click OK to generate the projection conversion formula.

In method 1, we dynamically change the projection of the map, and then use the data export method to re-generate the conversion projection layer. Here, we can directly use the project commands under data management tools \ projections and tranformations \ to generate the converted layer files. The project commands are located in the feature and raster directories respectively, split pins for vector and raster data. In this command, after the input layer is specified, the input coordinate system automatically identifies the input projection. You must specify the output projection, if the two are the same as the input and input projection of the previously defined projection conversion formula, the previously defined formula name will appear in the geographic transformation drop-down box below. You can directly select it for use.

Click OK to generate the layer file without further operations.