Reproject Dataset

Function Description

Performs projection on a single dataset. For a vector dataset, the result data after conversion can be saved as a new dataset or the source dataset projection can be directly converted. For raster, image, or model datasets, after projection conversion, the result dataset needs to be saved as a new dataset.

Feature Entry

  • Start tab -> Data Processing group -> Project -> Reproject Dataset.
  • Toolbox -> Data Management -> Projection Settings -> Reproject Dataset.
  • In the Workspace Manager, select the context menu of the dataset that needs projection conversion -> Properties. In the dataset attribute panel, under the Coordinate System item -> Project button.

Parameter Description

  • Source Dataset: Sets the dataset that needs projection and its data source. The source coordinate system area displays detailed description information of the source dataset's coordinate system.
  • Conversion Method: Click the drop-down button to the right of the Conversion Method label. The pop-up drop-down menu list displays over a dozen reference system conversion methods provided by the system. Users can choose an appropriate reference system conversion method. For an explanation of the conversion methods, please refer to Reference System Conversion Methods. For information on the conversion methods and scope of application, please refer to Transformation Model.
Note:

Supports coordinate transformation for planar coordinate system datasets, providing a four-parameter transformation method. Does not support conversion between planar coordinate system and geographic coordinate system.

  • Projection Transformation Parameters: Select different conversion methods. Click the Settings button, and different parameters can be customized in the Parameter Settings dialog box.

    When selecting a three-parameter conversion method, such as Geocentric Translation, Molodensky, or Molodensky Abridged, in the Parameter Settings dialog box, you 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, in the Parameter Settings dialog box, you 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). The translation parameters are in meters; the rotation parameters are in arc-seconds; and the scale difference is in parts per million (ppm).

    • Scale Difference: Represents the scale stretching from the original coordinate system to the new coordinate system. When converting between planar coordinate systems, the scale difference needs to be set. Scale difference = unit conversion from original to target coordinates * 1,000,000. For example, when converting from a planar coordinate system in millimeters to one in meters, the scale difference parameter should be 1000.
    • Rotation Angle (X/Y/Z): Represents the rotation angle around the X/Y/Z axis, in arc-seconds, with a default value of 0.
    • Offset (X/Y/Z): Also known as translation, represents the offset along the X/Y/Z axis, in meters, with a default value of 0.
    • Origin Coordinates (X/Y/Z): Represents the coordinate values of the rotation origin X/Y/Z, with a default value of 0.
    • Import/Export Projection Transformation Parameters File: Click the Import button at the bottom of the Parameter Settings 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 project's parameters. Click the Export button at the bottom of the Parameter Settings dialog box to export the currently set parameters to a specified path for future use.
  • Result Save As: Sets the name of the result dataset after projection and the data source where it is saved.
  • Target Coordinate System: Provides three setting methods, as described below. After setting the target projection, the details of the target projection will be displayed in the "target coordinate system" area.
    • Reset Coordinate System: Click the "Reset Coordinate System" button, select "More" in 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, and the "Copy Coordinate System" dialog box pops up. You can choose to copy from a data source or from a dataset:
      • From Data Source: Select the "From Data Source" radio button, click the combo box drop-down button, select a data source, and set its coordinate system as the target coordinate system.
      • From Dataset: Select the "From Dataset" radio button, click the combo box drop-down button, select a dataset, and set its coordinate system as the target coordinate system.
    • Import Coordinate System: Click the "Import Coordinate System..." button. In the pop-up "Select" window, select a projection information file and import it. Supports importing Shapefile projection information files (*.shp;*.prj), MapInfo Exchange Format (*.mif), MapInfo TAB File (*.tab), image format projection information files (*.tif;*.img;*.sit), and projection information files (*.xml).
  • Model Convert Vertex Option: This option is only available when the source data is a model dataset. For model datasets, the Model Convert Vertex option is checked by default to prevent misalignment after object coordinate transformation.
Note:
  • Any projection has projection distortion. Therefore, the transformation process between different projections is usually not completely reversible. That is, map data can be projected from its original projection to some other projection, but it cannot always be converted back precisely. Therefore, users should back up the original file before projection. Moreover, the number of projection transformations should be minimized to make the projection transformation results more accurate.
  • Each projection is designed to reduce distortion in a given characteristic for a given area. Therefore, each projection has a certain scope of application. When performing projection transformations, it should be done between coordinate systems with similar ranges as much as possible; otherwise, the accuracy of the projection transformation results is difficult to guarantee. For example, converting a world map in Mercator projection to Gauss projection can only ensure accuracy near the central meridian. Areas far from the central meridian will cause significant distortion.
  • In practical work, which conversion method to use depends on the specific situation. To determine the parameters, please purchase authoritative survey data or verify the correctness of the parameters using known control points in both coordinate systems.
  • After projection of text, the height and angle of the text will be converted accordingly. If you do not need such changes, you need to reset the height and angle of the converted text.
  • After reprojecting the dataset, the tolerance of the result dataset will be updated according to the new projection.

Related Topics

Batch Reproject

Transform Coordinates

Calculate Transformation Model Parameters