Monday, January 10, 2011

Reprojecting a grid file in SAGA GIS to a new coordinate system

There are SAGA GIS modules to perform re-projection of grid and shape layers from one coordinate system to another coordinate system. The workflow is quite straightforward. The only inconvenience is having to define the source and destination coordinate system each time you run the projection module.

Below is an example of projecting a grid layer from UTM Zone 16, NAD83 datum to geodetic latitude and longitude.
  1. Start up SAGA GIS. Load in a grid layer.
  2. Select Modules | Projection | Grid | Proj.4 (Dialog, Grid).

    The Proj.4 (Dialog, Grid) dialog box appears.

  3. Select the Source Projection Parameters row. Click the [...] button.

    The Source Projection Parameters dialog box appears.

  4. Select the Projection Type row. Choose a projection e.g. Universal Transverse Mercator (UTM).
  5. Select the Predefined Datum row. Choose a datum e.g. [NAD83] North_American_Datum_1983.
  6. Click Okay.
  7. Select the Grid system row. Choose the grid layer's system e.g. 30;384x464y;545765x3831410y.
  8. Select the Source row. Choose the grid layer name e.g. 01.9894CATD.
  9. Select the Target Projection Parameters row. Click the [...] button.

    The Target Projection Parameters dialog box appears.

  10. Select the Projection type row. Choose the destination projection e.g. Lat/long(Geodetic).
  11. Select the Predefined Datum row. Choose the datum e.g. [WGS84]. Click OK.


  12. Click OK.

    The Universal Transverse Mercator (UTM) dialog box appears
    .

  13. In the Zone field, type in 16. Click Okay.

    The User Defined Grid dialog box appears.

  14. If necessary, change the values. Click Okay.

    A new grid layer is created with the target coordinate system. 

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