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 operates as a wizard that depends on how many grids are specified to be reprojected in the first 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 the coordinate system you would like for the new grid. You may also define a grid 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 and a string prefix and/or postfix that will be used to create names for the output reprojected grids.

Reproject Grid File(s) dialog options

Grid file(s)

Specify one or more grid files to be reprojected. To specify multiple grids, use the Browse button and select multiple grid file names using the keyboard ctrl key. For multiple grids, all grid files must be of the same type. Script Parameter: GRIDREPJ.OLDGRID

Single-grid Process

If you have specified a single grid file, you will be presented with the coordinate system of the specific grid. Select the [Modify] button to change the coordinate system. You will only do this if the grid coordinate system has not been defined or it is incorrect.

You will then be asked to specify a new grid file name. If the grid does not exist the coordinate system of the original grid will be presented as a starting point for you to define the coordinate system of your new grid. Again, select Modify to modify the coordinate system.

You will then be presented with the new grid file cell size, dimensions and origin. If the reprojected coordinate system is dimensionally close to the original coordinate system (within 5%), the new cell size will be the same as the original cell size. Otherwise a new cell size will be chosen such that the grid will have approximately the same number of grid points as the original grid. Select the CellSize button if you would like to change the cell size.

Press Finish to reproject the grid.

Multiple-grid process

For multiple grids you will be presented with the coordinate system of the first input grid as a starting point from which you must select the Modify button to define the desired output coordinate system. All grids will be reprojected to the coordinate system you specify. Note that each input grid may have a different coordinate system.

You will be asked to specify a prefix and/or postfix that will be used to create new grid file names from the original grid names. If you specify nothing, the postfix "_reprojected" will be appended to the input file names to create the reprojected file names.

Press Finish to reproject all grids.

Application Notes

Some projections are not accurate beyond a certain distance from the central meridian or the parallels. For example, the common Transverse Mercator projection used in UTM, is only accurate to within about 10 degrees of the central meridian. To prevent location errors, the new bounding area for the output grid will only be as large as the projection can accurately convert coordinates to within 0.005% of the largest dimension of the grid. 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.