The workflow and tools to create mosaic datasets

This topic applies to ArcEditor and ArcInfo only.

There are two types of mosaic datasets—those used to manage, display, serve, and distribute raster data, and those created from existing raster catalogs or mosaic datasets. All the geoprocessing tools to create, edit, and manage a mosaic dataset are grouped together in the Mosaic Dataset toolset in the Data Management toolbox.

When you create a mosaic dataset that will be used to manage, display, serve, and distribute raster data, you will use the Create Mosaic Dataset tool.

General workflow

1. The mosaic dataset is created in a geodatabase. If you don't have a geodatabase, you first need to create one.
2. Create the mosaic dataset using the Create Mosaic Dataset tool.

   This creates an empty mosaic dataset and its schema in the geodatabase.

3. Add raster data using the Add Rasters to Mosaic Dataset tool.
   Tip:

   Before you add your raster data, you may first want to calculate its statistics and pyramids. This is especially useful when you're adding tiled or preprocessed raster datasets, such as DOQ orthophotos. By calculating the statistics, you can be sure the data will display correctly, and having pyramids can reduce the number of overviews that will be generated for the entire mosaic dataset. If you don't do this prior to adding the raster datasets to the mosaic dataset, you can calculate them at the time of adding them by checking the option on the tool's dialog box or afterwards using the Build Pyramids and Statistics tool. Note that pyramids are not necessary for the CADRG/ECRG, CIB, and DTED raster types.

   • Calculate cell size ranges—Use the Update Cell Size Ranges check box on the tool to do this at the time of ingest or later using the Calculate Cell Size Ranges tool.

     Cell size ranges are used to determine what rasters are processed to create the mosaicked image from the mosaic dataset and must exist in the attribute table.

   • Build the boundary of the image service—Use the Update Boundary check box on the tool to do this at the time of ingest or later using the Build Boundary tool.

     The boundary is the extent of all the raster datasets, defined by their footprints, within the mosaic dataset and must exist.

   • Generate overviews—Use the Update Overviews check box on the tool to do this at the time of ingest or later using the Build Overviews tool.

     Mosaic dataset overviews are lower-resolution images created to increase the display speed and reduce the CPU usage, since fewer rasters are examined to display the mosaicked image. They take time to create; therefore, for a large mosaic dataset, you may want to build them when your system is not busy with other operations.

4. View the mosaic dataset.

   When it's added to ArcMap, you will see several different layer types. You can use the Image layer to explore the mosaicked image. Any modifications you make in the Image layer are limited to your desktop and will not affect the properties of the mosaic dataset.

5. Serve as an image service using ArcGIS Server or make available locally.

You can create a model or write a script to create the mosaic dataset and add the data. The model below uses three tools—one to create a new geodatabase, one to create the mosaic dataset, and another to add the raster data. There are options in the Add Rasters To Mosaic Dataset tool to calculate the cell size ranges, build the boundary, and generate the overviews. These options can be checked on, so when the model finishes, a complete mosaic dataset will be created and be ready to serve.

When you create a mosaic dataset you can view it as a mosaicked image or as a catalog (or table). Each raster dataset is added as a row in the mosaic dataset's attribute table and is represented by a footprint polygon. Each column in the table is an attribute of the raster dataset; you can add or modify many of these columns and perform queries based on these fields. Additionally, if you serve the mosaic dataset as an image service, you can define which field users can use in their own queries. Defining which fields are visible in an image service is one of the properties you can set on the mosaic dataset.

Learn about the mosaic dataset properties

You can modify the mosaic dataset using the geoprocessing tools or you can perform additional modifications, such as editing the footprints, within ArcMap. When you add a mosaic dataset to ArcMap, it will be added as custom group layer. By default, you will see a Boundary, Footprint, and Image layer. You can use the editing tools in ArcMap to edit the polygons of the Boundary and Footprint layers.

A log table is persisted within the mosaic dataset to keep a record of all the processes performed on the mosaic dataset and their time duration, such as adding rasters, calculating cell size ranges, and building overviews. Generally, you will not modify this log, but if you need to empty the log table, right-click the mosaic dataset in ArcCatalog or the Catalog window and click Remove > Clear Logs.

When you create a mosaic dataset from a raster catalog or another mosaic dataset, you use the Create Referenced Mosaic Dataset tool. When you create a referenced mosaic dataset, you can edit its properties and the boundary. You are not able to edit the footprints or any of the other characteristics of the referenced mosaic dataset. This is a quick way to serve a raster catalog or distribute a mosaic dataset where users can modify the properties of the original.