Defining or modifying a raster's coordinate system

1. In ArcCatalog or the Catalog window, right-click the raster whose coordinate system you want to define and click Properties.
2. Scroll down to the Spatial Reference section, and click Edit.
3. On the Spatial Reference Properties dialog box, do either of the following:
   • Click Select and choose a predefined coordinate system. Browse to the coordinate system folder, click the one that is required for your raster dataset, then click Add. You may need to open several folders before you can choose your correct projection.
   • Click Import and choose the data source whose coordinate system parameters you want to copy.
   • Click New, click Geographic or Projected, then define a new, custom coordinate system.
4. Click OK on the Spatial Reference Properties dialog box.
5. Click OK on the Raster Dataset Properties dialog box.