Creating a mosaic

An imagery mosaic is a container that allows multiple imagery sources to be processed as one unit. A mosaic maintains its constituent images intact, without masking or feathering the edges where they meet. Only the external edges of the mosaic are masked and feathered.

This article covers deciding when to create a mosaic, creating a mosaic, and modifying a mosaic.

Deciding when to create a mosaic

If you have a collection of images whose edges perfectly abut each other, it's often a good idea to create a mosaic before adding the images to a layer. For example, imagery for a city might include a number of images. If you add those images directly to a layer, their edges are feathered, and some detail may be lost. However, if you add the images to a mosaic first, the edges of the individual images where they meet are maintained.

Mosaics are meant for contiguous images. Although technically, you can create a mosaic from non-contiguous images, there wouldn't be a reason to do so.

The images in a mosaic must match in the following ways:

  • resolution
  • projection
  • number of bands
  • standard North/South orientation

Creating a mosaic

To mosaic images, you should first tag the images, then do a search, and then add all the search results to a mosaic.

You'll need to fill in the following information.

Name The name of this mosaic.
Description A text description for this mosaic. This description will be visible only within Google Maps Engine and not to external viewers of a map that includes this mosaic.
Tags The text strings in response to which you want this mosaic to be found.
Sharing settings The access list to which you want to grant permission to work with this mosaic.
Attribution Acknowledgment for the source of the imagery.

Note: It's better to process the mosaic before adding it to a layer. During processing, you'll get an error if the images in the mosaic don't match in terms of the attributes mentioned at the top of this article (resolution, projection, number of bands, standard North/South orientation).

When the mosaic is processed, you can add it to a layer as you would any other image data source.

Modifying a mosaic

You can add images to a mosaic and remove images from a mosaic. When you make changes to a mosaic, you must reprocess the mosaic and reprocess any layer that contains the mosaic.