Monday, October 10, 2011

Set Coordinate Reference System for a grid file in SAGA GIS

When an ESRI ArcGrid ASCII Grid file without an associated projection file (*.prj) is loaded into SAGA GIS, the grid data will be placed in a plain cartesian X and Y reference frame. If the description of the grid layer is displayed in SAGA GIS, then it will show as Undefined Coordinate System for the Projection as shown below.
SAGA GIS has a function to set the grid file's coordinate reference system; the workflow is shown below.

  1. Select Modules | Projection | Set Coordinate Reference System.

    The Set Coordinate Reference System dialog box appears.

  2. Select the Dialog field. Click the [...] button.

    The Dialog appears.
  3. In the Projection Type field, choose an appropriate projection e.g. Universal Transverse Mercator (UTM).
  4. Click the Projection Settings field. Then click the [...] button.

    The Universal Transverse Mercator dialog box appears.

  5. In  the Zone field, type in a value e.g. 32. Toggle on South if necessary. Click Okay.
  6. If necessary, define any other settings appropriate for the coordinate reference system. Click Okay.
  7. Click the Data Objects Grids field. Click the [...] button.

    The Grids dialog box appears.
  8. Select one or more grid layers on the left e.g. 01. ground. Click the > button. Click Okay.

  9. Click Okay.

    The defined coordinate reference system is assigned to the selected grid layer(s).
  10. Selecting the grid layer and displaying the description shows that the grid layer has been assigned the new projection parameters.

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