Reproject Grid File(s)

Use the Grid and Image > Utilities > Reproject Grid File(s) menu option (GRIDREPJ GX) to reproject one or more grids to a new coordinate system. The GX functions as a wizard, adapting its workflow based on the number of grids selected in the initial dialog.

If you are reprojecting a single grid, you will be able to view and modify the coordinate system of the input grid, specify a new reprojected grid file, and choose the coordinate system for the reprojected grid. You may also define the cell size for the new grid.

If you are reprojecting multiple grids, you can select any number of grids of the same type. You can then define the desired coordinate system for all output grids, along with a string prefix and/or postfix to generate names for the reprojected grids.

Reproject Grid File(s) dialog options

Grid file(s)

Specify one or more grid files to reproject. Use Browse and hold Ctrl to select multiple files. All selected grids must be of the same type.

Script Parameter: GRIDREPJ.OLDGRID

Single Grid Reprojection

If you are reprojecting a single grid:

  • You'll first see the current coordinate system of the input grid. Click Modify to change it—only necessary if the system is undefined or incorrect.

  • Next, specify a name for the new grid file. If the file doesn't exist, the original grid's coordinate system will be used as a starting point. Again, click Modify to adjust it. You can transform between local datum transforms (LDTs). See the Help content associated with the Coordinate System dialog for more information.

  • You'll then define the new grid's cell size, dimensions, and origin. If the new coordinate system is within 5% of the original, the new cell size will be the same as the original cell size. Otherwise, a new cell size will be calculated to maintain a similar number of grid points as the original grid.

  • To manually adjust the cell size, click CellSize.

  • Click Finish to complete the reprojection.

Multiple Grid Reprojection

If you are reprojecting multiple grids:

  • Select multiple grid files of the same type using the Browse button and the Ctrl key.

  • The coordinate system of the first grid will be shown. Click Modify to set the desired output coordinate system for all selected grids.

    Input grids may have different coordinate systems.

  • Specify a prefix and/or postfix to generate new file names. If left blank, "_reprojected" will be appended by default.

  • Click Finish to reproject all grids.

Application Notes

Some projections have limited accuracy beyond a certain distance from the central meridian or the parallels. For example, the Transverse Mercator projection (used in UTM) is only reliable within ~10° of the central meridian.

To avoid location errors, the bounding area of the output grid is restricted to the portion where the projection can maintain precision within 0.005% of the grid’s maximum extent. If your output grid appears to be cut off in one or more dimensions, it is probably because you are using a projection that cannot be converted accurately in those regions.

See Also: