The Mosaic button creates a layer containing a mosaic created from the selected rasters in the Image Analysis window. The overlap between the mosaic layers can be controlled by choosing a mosaic operator:
- First—The overlapping areas will contain the cells from the first raster dataset listed in the source.
- Last—The overlapping areas will contain the cells from the last raster dataset listed in the source.
- Min—The overlapping areas will contain the minimum cell values from all the overlapping cells.
- Max—The overlapping areas will contain the maximum cell values from all the overlapping cells.
- Mean—The overlapping areas will contain the mean cell values from all the overlapping cells.
- Blend—The overlapping areas will be a blend of the cell values that overlap; this blend value relies on an algorithm that is weight based and dependent on the distance from the cells to the edge within the overlapping area.
- Sum—The overlapping areas will contain the total sum of the cell values from all the overlapping cells.
You can specify the overlap option, then click the Mosaic button 
, or you can click the resultant mosaic layer in the Image Analysis window and change the overlap option, and it will change dynamically.
The order in which the rasters are mosaicked together is dependent on their order in the table of contents.
- To view the Image Analysis window in ArcMap, click Windows on the main menu and click Image Analysis.
- Select two or more layers in the Image Analysis window.
- Optionally, click the Mosaic drop-down arrow and select an operator.
- Click the Mosaic button .
- To change the mosaic operator, select the mosaic layer in the Image Analysis window and click the Mosaic drop-down arrow to select an operation that will be applied to the overlapping areas.