Merging rasters

Sometimes you want to analyze an area that falls on more than one raster. To analyze the entire area, you must perform the steps of your analysis multiple times, once for each raster. Such a process could be time-consuming and error-prone, especially if you have a large number of rasters or a multi-step analysis. However, by first combining the individual rasters to create a single larger raster, you'll only need to perform the analysis steps once.

Rasters can be combined as long as they share the same spatial reference and are of the same type, for example vegetation.

Perhaps you want to analyze the variety of the vegetation in a particular agricultural or wildlife management area using a vegetation raster. Your area of interest happens to fall near the edge of the raster, so you need two different rasters to see the entire region.

There are a few things you'll need to check before you combine rasters.

First, the input rasters may be totally overlapping, partially overlapping, perfectly adjacent, or entirely separated, as long as they are in the same coordinate system.

Second, the input rasters must be of the same type. For example, you could combine a soils raster with one or more soils rasters or an elevation raster with another elevation raster.

Third, you need to know if you are combining discrete or continuous rasters because the method used to join each type differs in how it handles areas where the input rasters overlap.