Feature Description

Project the source dataset according to the target coordinate system. The result will directly change the projected coordinate system of the source dataset. Currently, only vector datasets support coordinate system transformation.

Depending on the set "projection conversion method," the parameters of this tool will also vary. The projection conversion method can generally be summarized into three-parameter conversion method and seven-parameter conversion method:

1. Three-Parameter Conversion Method

   When converting reference systems, a relatively simple conversion method is the so-called three-parameter conversion method. The mathematical model underlying this conversion method assumes that only the spatial coordinate origin is translated between two geodetic reference systems, without considering other factors (see Figure 1). This method inevitably produces three parameters: translation amounts in the X, Y, and Z directions. The three-parameter conversion method is simple to calculate but has low accuracy, and is generally used for conversions between different geocentric space rectangular coordinate systems.

2. Seven-Parameter Conversion Method

   The seven-parameter method is based on a mathematical model that considers not only the translation of the coordinate system but also factors such as coordinate system rotation and scale differences. Therefore, in addition to three translation amounts, it requires three rotation parameters (also known as three Euler angles) and a scale factor (also called scale factor). The conversion 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. The scale factor represents the scale change from the original coordinate system transformation to the new coordinate system. Generally, the unit of translation factors is meters (consistent with the unit), the unit of rotation angle is seconds, and the unit of scale factor is one in a million.

3. The Geocentric Translation method, Molodensky conversion method, and simplified Molodensky (MolodenskyAbridged) conversion method belong to projection conversion methods with lower accuracy. The three-parameter conversion method requires three translation transformation parameters (ΔX, ΔY, ΔZ), and the Molodensky conversion method and simplified Molodensky conversion method also require three translation transformation parameters (ΔX, ΔY, ΔZ). These methods can generally be adopted when data accuracy requirements are not high.

4. Position Vector method, Coordinate Frame method (based on geocentric), and Bursa-Wolf method belong to several conversion methods with higher accuracy. They require seven parameters for adjustment and conversion, including three translation transformation parameters (ΔX, ΔY, ΔZ), three rotation transformation parameters (Rx, Ry, Rz), and one scale parameter (S). These methods are identical, but due to differences in countries, regions, or surveying schools, the customary names vary.

In practical work, which conversion method to adopt depends on the specific situation. Whether the conversion result is satisfactory depends on the setting of transformation parameters. Transformation parameters can be obtained from official surveying agencies or data providers; they can also be measured and calculated independently. The suitability of transformation parameters must be determined through control points that exist in both reference systems.

Parameter Description

Parameter Name	Default Value	Parameter Interpretation	Parameter Type
Source Data		The source dataset to undergo coordinate system transformation. In the iServer GPA WebUI interface, you can specify the dataset by clicking the "Set" button on the right side of the parameter and completing it in the "Set Connection Info" dialog box, and it supports datasets from multiple datasource types. Additionally, you can use the "Open the Dataset" tool to open a dataset, and then assign the returned dataset to the "Source Data" input parameter of the "Dataset Coordinate System Transformation" tool via connection, as shown in the figure below. This way, when the model executes, the opened dataset is dynamically assigned to the corresponding parameter of the "Dataset Coordinate System 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 source data conversion. In the iServer GPA WebUI interface, this parameter requires inputting the EPSG code corresponding to the coordinate system. For example: a parameter value of 4326 represents the WGS 1984 geographic coordinate system; while in the iDesktopX GPA interface, this parameter can be set via a dialog box, as shown below: .	PrjCoordSys
Scale Difference	0.0	This parameter is the scale factor, representing the scale change from the original coordinate system transformation to the new coordinate system.	Double
Rotation Angle X	0.0	Rotation transformation parameter, indicating the rotation angle of the X-axis, with the unit in seconds.	Double
Rotation Angle Y	0.0	Rotation transformation parameter, indicating the rotation angle of the Y-axis, with the unit in seconds.	Double
Rotation Angle Z	0.0	Rotation transformation parameter, indicating the rotation angle of the Z-axis, with the unit in seconds.	Double
Offset X	0.0	Coordinate offset of the X-axis (offset is also called translation amount).	Double
Offset Y	0.0	Coordinate offset of the Y-axis (offset is also called translation amount).	Double
Offset Z	0.0	Coordinate offset of the Z-axis (offset is also called translation amount).	Double
Rotation Origin X Coordinate	0.0	The X-coordinate amount of the rotation origin.	Double
Rotation Origin Y Coordinate	0.0	The Y-coordinate amount of the rotation origin.	Double
Rotation Origin Z Coordinate	0.0	The Z-coordinate amount of the rotation origin.	Double
Projection Conversion Method	MTH_GEOCENTRIC_TRANSLATION	The method used for projection. SuperMap provides several common projection conversion methods. For details, refer to the "Projection Conversion Method" table below.	CoordSysTransMethod

Table: Projection Conversion Method

Output Result