Create a mosaic dataset

Available with Standard or Advanced license.

Mosaic datasets are used to manage, display, publish, and distribute imagery. You can create, edit, and manage them with the tools in the Mosaic Dataset toolset in the Data Management toolbox.

When you create a mosaic dataset, it is created as an empty container in the geodatabase with some default properties to which you can add image data. You must have write access to that geodatabase and an ArcGIS AllSource Standard or ArcGIS Pro Advanced license.

Create and add data to a mosaic dataset

To create a mosaic dataset and add data to it, complete the following steps:

1. Create the mosaic dataset.
   1. Right-click the geodatabase in the Catalog pane and click New > Mosaic Dataset to open the Create Mosaic Dataset tool. Alternatively, you can directly open the Create Mosaic Dataset tool from the Geoprocessing pane.

      If you do not have a geodatabase for the mosaic dataset, create one using the Create File Geodatabase tool.

   2. Specify the values for Mosaic Dataset Name and Coordinate System.

      The coordinate system does not need to match the raster data you are adding; however, it will be used to create additional components, such as the boundary and footprints. It will also be the default spatial reference of the mosaic dataset when it is accessed. Any raster datasets in a different spatial reference will be reprojected on the fly to create the mosaicked image.

2. Add data to the mosaic dataset.
   1. To add images, right-click the mosaic dataset in the Catalog pane and click Add Rasters to open the Add Rasters to Mosaic Dataset tool tool. Alternatively, you can directly access and open the Add Rasters to Mosaic Dataset tool tool in the geoprocessing pane. For the Input Data parameter, specify File to select individual image files, Folder to include all the image files in a directory, or Dataset to include the raster datasets contained in a geodatabase.
   2. Specify the values for Mosaic Dataset and Raster Type.
   3. Check Update Overviews in the Mosaic Post-processing section.

   The Add Rasters to Mosaic Dataset tool tool adds the data, calculates the required information, and generates the overviews. Once it's complete, the mosaic dataset is ready to use or publish.

When you add a mosaic dataset to a map, it is added as a custom group layer. By default, the Boundary, Footprint, and Image layers are present. To learn more about this custom group layer, see Types of layers in a mosaic dataset layer.

Note:

If the spatial reference systems of the data and the mosaic dataset are based on different spheroids, you may need to define a specific geographic transformation. You can define the transformation in two locations. When adding imagery to the mosaic dataset that has a different datum than the mosaic dataset, set the Geographic Transformations value on the Environment Settings dialog box. If you want the datum of the mosaic dataset to be different than the source imagery, open the mosaic dataset properties from the Catalog pane, click the Defaults tab, and set the Geographic Coordinate System Transformation property.

Tip:

A referenced mosaic dataset is a particular type of a mosaic dataset. This mosaic dataset has limitations and is typically used to distribute a mosaic dataset so users cannot modify the properties of the original, and to provide additional ways to view the data in a mosaic dataset.

For more information about referenced mosaics, see Source, derived, and referenced mosaic datasets.

Added functionality

You can create a mosaic dataset by defining the name and spatial reference system (as shown in the steps above), but there are additional parameters to help you create mosaic dataset products that suit your application needs, such as the pixel type, number of bands, and band wavelength information. You can also refine mosaic datasets by defining properties such as the display defaults, by defining processing templates, and by refining the inputs, such as editing their footprints.

Refine the mosaic dataset

In the steps in the previous section, you did not set properties or modify the tool parameters. There are additional parameters for the Create Mosaic Dataset tool that you can use to customize the mosaic dataset. These control the product properties and the pixel properties of the mosaic dataset, which can impact the characteristics of the mosaic dataset, and the outputs.

Product properties

The product definition parameter allows you to customize the mosaic dataset to contain data with a specific number of bands and wavelengths. The product definition controls how the data is added to the mosaic dataset and how it displays by default, and aids in some processing.

The following are the most commonly used product definitions:

• Natural color—This creates a three-band mosaic dataset, with red, green, and blue wavelength ranges.
• Natural color and infrared—This creates a four-band mosaic dataset, with red, green, blue and near-infrared wavelength ranges.
• Color infrared—This creates a three-band mosaic dataset, with near-infrared, red, and green wavelength ranges.

Using a product definition helps when adding data containing wavelength information in its metadata. If the wavelength information is ordered differently in the inputs, it will all be ordered correctly when added to the mosaic dataset. For example, if band 1 in a QuickBird scene is a blue wavelength, and band 3 in the mosaic dataset is designed to contain the blue wavelengths, the QuickBird scene's blue band will be mapped to the mosaic dataset's blue band. Without this product definition, the QuickBird scene's blue band may be mapped to the mosaic dataset's red band. The correct ordering is shown below.

Additional product definitions are designed to support specific satellite imagery products, such as Sentinel, Landsat, and WorldView. You can also create a custom product definition in which you define the number of bands, their order, and their wavelength ranges by editing the Product Band Definitions parameter.

Dive-in:

If you create a mosaic dataset using a product definition with fewer bands than the input, the extra bands will be excluded from the mosaic dataset. For example, if the mosaic dataset's product definition is natural color, and the input has five bands, two of the bands will be excluded from the mosaic dataset. The excluded bands will be those with wavelength ranges furthest from the ranges defined for the natural color bands—red, green, blue (RGB).

If there are more bands in the mosaic dataset than in the input, the mosaic dataset will not contain an empty band. The band with the wavelength closest to the extra band will be used. In this case, image bands will be duplicated in the mosaic dataset.

If the input doesn't have wavelength information, it can be added to the mosaic dataset, but you need to ensure that the bands are added in the correct order. You may need to use the Extract Bands function to map the bands in a different order than how they are stored in the image source file.

Pixel properties

As an alternative to specifying a product definition, you can define the number of bands and the output pixel type in the mosaic dataset. The number of bands and pixel type are properties of the mosaic dataset, similar to a raster dataset. If these are not defined when you create the mosaic dataset, they are identified by the application. By default, this information is derived from the first raster added to the mosaic dataset or altered by functions you may add that change the defaults.

If you're combining the types of raster data used in the mosaic dataset, it is recommended that you define these values. For example, if using raster data from a single-band orthoimage and a three-band orthoimage, you need to specify three bands; otherwise, if the single-band orthoimage is added first, only the first band of the three-band orthoimage will be added. Also, if you're mixing elevation data sources, the inputs may have a mix of pixel types. By defining a pixel type, such as 32-bit floating point, you won't lose any information if the first input added is 8 bit and the other inputs are larger.

Add data to the mosaic dataset

The Add Rasters to Mosaic Dataset tool has many options. Common parameters and defaults include the following:

• Ensure the Update Cell Size Ranges check box is checked when adding data. Cell Size Rangesare used to determine which rasters are processed to create the mosaicked image from the mosaic dataset and must exist. If you plan to immediately add more data, you may choose to calculate the cell sizes for all data at the same time rather than each time you add data, since the existing data and new data will be analyzed and values will be recalculated or calculated. You can check this option the final time you add data to the mosaic dataset, or use the Calculate Cell Size Ranges tool.
• Ensure the Update Boundary check box is checked when adding data. The boundary is the extent of all the raster datasets, defined by their footprints. As with the previous parameter, if you're adding additional data immediately after, you can choose to calculate the boundary after all the data has been added.
• Ensure the Update Overviews check box is checked when adding data. 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. Build the overviews once all the data is added to the mosaic dataset (as with the previous parameters). 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. If you choose to generate these at another time, use the Build Overviews tool.
• Ensure the Include Sub Folders check box is checked when the data is located within a subfolder within the specified folder. This option recursively explores any subfolders containing the data being added.
• If your workspace contains duplicate data, you can change the Add New Datasets Only parameter to exclude duplicates. This may be useful; however, it takes more time because it must check every new item with one that is already added.
• If the data doesn't have statistics, you can check Calculate Statistics. This is useful for data that has not been preprocessed (enhanced). If the dataset already includes statistics, they are not recalculated.
• If the data doesn't have pyramids, you can check Build Raster Pyramids. Pyramids reduce the number of overviews that are generated for the entire mosaic dataset. If the dataset already has pyramids, they are not recalculated. Pyramids are not necessary for the CADRG/ECRG, CIB, and DTED raster types.
• To restrict the data in your workspace that is added, you can define a filter for the File Filter parameter, which performs a file name search. For example, there may be thumbnail images stored with the original data. If you're using the Raster Dataset raster type, you can specify the valid file extension (such as *.tif) so the thumbnails (such as *.gif) are not added.

When you run the tool to add the data to the mosaic dataset, footprints are created for each raster dataset and the attribute table is populated with each raster. Depending on the options you selected, cell sizes, overviews, pyramids, statistics, and the boundary are created.

Modify the properties

Properties can be set on the mosaic dataset that affect how the mosaicked image will be presented to the user (or client) and how they might interact with it. They can also impact the performance of the server or image service if the mosaic dataset is published.

You can access the Mosaic Dataset Properties dialog box from the Catalog pane or by right-clicking the mosaic dataset and clicking Properties. Here, you can make modifications to these properties. You can edit the values on the dialog box by clicking the value next to the property. You can either type a different value or make a selection from a list. You can also use the Set Mosaic Dataset Properties tool to modify the properties.

Two common properties to set are the compression method and mosaic methods. The compression method can affect the transmission speed. It is recommended that you set a compression method to transmit the mosaicked image more quickly than without compression. If you serve the mosaic dataset as an image service, clients can modify this setting to decompress the mosaicked image if they prefer. The mosaic method defines the order in which the images are mosaicked together to create the image. You can choose one or more allowable mosaic methods and which one will be the default. The user can choose from the methods you select.

Properties set on the mosaic layer in the Contents pane only apply to the layer and are not stored with the mosaic dataset, such as the band combination or mosaic method. If there are multiple users of the mosaic dataset, they will not be impacted by a layer setting used by another user. This is the same behavior as any dataset and layer. The mosaic dataset properties can be configured in the map or by modifying the default values of the mosaic dataset.

Automate the workflow

You can create a model or write a script to create the mosaic dataset, add the data, and edit the properties. The model below uses three tools: one to create a geodatabase, one to create the mosaic dataset, and another to add the images. The Add Rasters To Mosaic Dataset tool has options to calculate the cell size ranges, build the boundary, and generate the overviews.