Transform Coordinates

Feature Description

If a user needs to transform the coordinates of a point from one coordinate system to another, they can use the "Transform Coordinates" function to obtain the coordinate values of that point in other coordinate systems.

Transform Coordinates supports conversion between two geographic coordinate systems, two projected coordinate systems, and also mutual conversion between a geographic coordinate system and a projected coordinate system.

Feature Entry

  • Start tab -> Data Processing group -> Project drop-down button -> Transform Coordinates.

Steps

  1. Source Data Point: Directly input the longitude and latitude or X/Y coordinate values of the point. If the source coordinate point is projected in a geographic coordinate system, you can switch to "Display in Degrees:Minutes:Seconds" format to input the specific degrees, minutes, and seconds values.
  2. Source Coordinate System: Set the coordinate system of the source data at the source coordinate system. The Transform Coordinates function does not support planar coordinate transformation; the coordinate systems of the source data and target dataset can only be set to a geographic coordinate system or a projected coordinate system. Coordinate system settings can be done in the following three ways:
      • Reset Coordinate System: Click the Reset Coordinate System button, select More from the drop-down menu, and set the target projection in the Coordinate System Settings dialog box. For specific operations on coordinate system settings, please refer to Projection Settings.
      • Copy Coordinate System: Click the Copy Coordinate System button to choose to copy from a data source or from a dataset.
      • Import Coordinate System: Click the Import Coordinate System... button to select a projection information file and import it.
  3. Target Coordinate System: Set the projected coordinate for the result coordinate point at the target coordinate system. Set the result coordinate system to a geographic coordinate system or a projected coordinate system different from the source coordinate system. The setting method is consistent with the projection settings of the source coordinate system.
  4. Reference Conversion Settings: Click the drop-down button to the right of the Conversion Method label. The drop-down menu that pops up displays over ten projection methods provided by the system. Users can choose an appropriate projection method. For a description of conversion methods, please refer to Reference System Conversion Method Description.
  5. Projection Transformation Parameters: Different conversion methods allow for different customizable parameters in the projection dialog box. For an introduction to different projection methods, please refer to Reference System Conversion Method Description.
    • When selecting a three-parameter conversion method, such as Geocentric Translation, Molodensky, or Molodensky Abridged, the "Projection" dialog box requires setting parameters for offsets in the X, Y, and Z directions.

      Users need to set three translation parameters, namely (ΔX, ΔY, ΔZ). This conversion is essentially a geocentric transformation, shifting from the center of one datum (0,0,0) to the center of another datum (ΔX, ΔY, ΔZ). The three-parameter transformation is a linear translation transformation, with units in meters.

    • When selecting a seven-parameter conversion method, such as Position Vector, Coordinate Frame, or Bursa-Wolf, parameters such as scale difference, rotation angle, and offset need to be set.

      Users need to set seven parameters: three linear translation parameters (ΔX, ΔY, ΔZ), three angular rotation parameters around the axes (Rx, Ry, Rz), and a scale difference (S). Translation parameters are in meters; rotation parameters are in "arc seconds"; and the scale difference is in parts per million (ppm).

  6. Import and Export Projection Transformation Parameters File: Click the import button at the bottom of the projection dialog box to import a projection transformation parameters file with the suffix *.ctp. This imports the parameter information saved in the file as the current projection parameters. Click the export button at the bottom of the projection dialog box to export the currently set parameters in the projection dialog box to a specified path for future use.
  7. After completing all parameter settings, click the "Convert" button to complete the Transform Coordinates operation. Users can view the Transform Coordinates result at the result coordinate point in the Transform Coordinates dialog box. If the target coordinate system is a geographic coordinate system, you can switch to display the result coordinate point coordinates in degrees:minutes:seconds format.
Notes:
  • Transform Coordinates is performed between different geographic coordinate systems or projected coordinate systems. If the source coordinate system is the same as the target coordinate system, no conversion will be performed, and a "Transform Coordinates Failed" pop-up box will appear as a prompt.
  • In practical work, which conversion method to adopt depends on the specific situation. For the determination of each parameter, please purchase authoritative survey data or verify the correctness of the parameters using known control points in both coordinate systems.

Related Topics

Reproject Dataset

Batch Reproject

Calculate Transformation Model Parameters