Feature Description

Projects a dataset based on the target projection coordinate system. The transformed dataset is saved in the target datasource.

The parameters of this tool differ depending on the "projection conversion method" set. The projection conversion methods can generally be categorized into three-parameter transformation methods and seven-parameter transformation methods:

1. Three-Parameter Transformation Method

   When transforming between reference systems, a simpler method is the so-called three-parameter transformation method. The mathematical model of this method assumes that only the spatial origin has shifted between the two geodetic reference systems, without considering other factors (see Figure 1). This method inherently produces three parameters: the translation amounts in the X, Y, and Z directions. The three-parameter method is computationally simple but less accurate. It is generally used for transformations between different geocentric space rectangular coordinate systems.

2. Seven-Parameter Transformation Method

   The mathematical model underlying the seven-parameter method considers not only the translation of the coordinate system but also factors such as coordinate system rotation and scale differences. Therefore, in addition to the three translation parameters, it requires three rotation parameters (also known as three Euler angles) and a scale factor. The transformation principle is shown in Figure 2. The three translation amounts are denoted by ΔX, ΔY, ΔZ; the three rotation transformation parameters are denoted by Rx, Ry, Rz; and the scale factor is denoted by S. Here, the scale factor represents the scale stretching amount from the original coordinate system transformation to the new coordinate system. Generally, the unit for translation parameters is meters (consistent with the unit), the unit for rotation angles is seconds, and the unit for the scale factor is parts per million.

3. The Geocentric Translation method, Molodensky method, and Molodensky-Abridged method are projection conversion methods with relatively lower accuracy. The three-parameter method requires three translation transformation parameters (ΔX, ΔY, ΔZ), as do the Molodensky and Molodensky-Abridged methods (ΔX, ΔY, ΔZ). These methods are generally acceptable when data accuracy requirements are not high.

4. The Position Vector method, Coordinate Frame method (based on geocentric), and Bursa-Wolf method are conversion methods with higher accuracy. They require seven parameters for adjustment and transformation, including three translation transformation parameters (ΔX, ΔY, ΔZ), three rotation transformation parameters (Rx, Ry, Rz), and one scale parameter (S). These methods are essentially identical, but their names differ due to regional or surveying school conventions.

In practical work, the choice of conversion method depends on the specific situation. Whether the transformation result is satisfactory depends on the setting of the transformation parameters. Transformation parameters can be obtained from official surveying institutions or data providers; they can also be derived from one's own measurements. The suitability of transformation parameters must be determined using control points that exist in both reference systems.

Parameter Description

Parameter Name	Default Value	Parameter Interpretation	Parameter Type
Source Dataset		The source dataset to be projected. In the GPA WebUI interface of iServer, you can specify the dataset by clicking the "Settings" button on the right side of the parameter, completing the specification in the "Set Connection Info" dialog, and it supports datasets from various datasource types. Additionally, you can use the "Open the Dataset" tool to open a dataset, and then assign the returned dataset via a connection to the "Source Dataset" input parameter of the "Dataset Projection Transformation" tool, as shown below. This way, when the model executes, the opened dataset is dynamically assigned to the corresponding parameter of the "Dataset Projection Transformation" tool. Thus, the "Source Data" input parameter of the "Dataset Coordinate System Transformation" tool can also be passed via connection from the result dataset output by other GPA tools.	Dataset
Target Coordinate System		The target coordinate system after the source data conversion. In the GPA WebUI interface of iServer, this parameter requires entering the EPSG code corresponding to the coordinate system, for example: a parameter value of 4326 represents the WGS 1984 geographic coordinate system. In the iDesktopX GPA interface, this parameter can be set via a dialog, as shown below: .	PrjCoordSys
Target Datasource		The specified datasource for storing the result dataset after projection. In the GPA WebUI interface of iServer, you can specify the datasource by clicking the "Settings" button on the right side of the parameter, completing the specification in the "Set Connection Info" dialog, and it supports various datasource types. Additionally, you can use the "Open Datasource" tool to open a datasource, and then assign the returned datasource via a connection to the "Target Datasource" input parameter of the "Dataset Projection Transformation" tool, as shown below. This way, when the model executes, the opened datasource is dynamically assigned to the "Target Datasource" parameter.	Datasource
The Name of the Resulting Dataset		Specifies the name of the result dataset after projection.	String
Scale Difference	0.0	This parameter is the scale factor, representing the scale stretching amount from the original coordinate system transformation to the new coordinate system.	Double
Rotation Angle X	0.0	Rotation transformation parameter, representing the rotation angle of the X-axis, unit: seconds.	Double
Rotation Angle Y	0.0	Rotation transformation parameter, representing the rotation angle of the Y-axis, unit: seconds.	Double
Rotation Angle Z	0.0	Rotation transformation parameter, representing the rotation angle of the Z-axis, unit: seconds.	Double
Offset X	0.0	Coordinate offset (also called translation) for the X-axis.	Double
Offset Y	0.0	Coordinate offset (also called translation) for the Y-axis.	Double
Offset Z	0.0	Coordinate offset (also called translation) for the Z-axis.	Double
Rotation Origin X Coordinate	0.0	The X-coordinate value of the rotation origin.	Double
Rotation Origin Y Coordinate	0.0	The Y-coordinate value of the rotation origin.	Double
Rotation Origin Z Coordinate	0.0	The Z-coordinate value of the rotation origin.	Double
Projection Conversion Method	MTH_GEOCENTRIC_TRANSLATION	The method used for projection. SuperMap provides several commonly used projection transformation methods; see the "Projection Conversion Method" table below for details.	CoordSysTransMethod

Table: Projection Conversion Method

Output Result