This tool will take two or more grids and merge them into one grid. Any area where data is missing will be filled in automatically with the grid???s No Data value.
Input grids should all be in the same projection.
To merge grids:
Click on [GIS Tools]
Click on [Raster]
Click on [Merge Grids]
Select the grid files to be merged
Select the output file format and storage location, and click [Finish]