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Many organizations have large collections of imagery acquired at various dates covering the same area. This data is often stored in different file formats, in different projections, and with different pixel sizes. For example, forestry companies may have imagery of their forest stands taken at different times of the year, or taken over different years, to help them manage their harvests. Also, many cities and states have large collections of orthoimagery acquired on an annual or semiannual schedule. These collections can be compiled into a single mosaic dataset that can be used on-premises or served as an image service to their clients.
The following workflows assume you have multiple years of orthoimagery that you want to compile into a single mosaic dataset where the user will see the most recent imagery by default. To do this, you will create multiple mosaic datasets—one mosaic dataset for each year—and a final primary mosaic dataset. This is the optimal design, because you can maintain each year's orthoimages in a single mosaic dataset collection and quickly add new collections to the primary mosaic dataset without impacting users.
Create a geodatabase
You will create the mosaic datasets in a geodatabase. You can use a single geodatabase or more than one. In this workflow, it is assumed that all the mosaic datasets are created in a single file geodatabase.
Right-click a folder in the Catalog pane and click New > File Geodatabase or use the Create File GDB tool. To set this new geodatabase as the default geodatabase, right-click it in the Catalog pane and click Make Default Geodatabase. This sets the current and scratch workspace location for the geoprocessing environment to this geodatabase.
Create a mosaic dataset for each year
Ensure that the image data is stored on disk in a location where it can be accessed to build the mosaic dataset. If this is where it will be served, the location also needs to be visible (read access) to ArcGIS Image Server. Mosaic datasets do not manage the raster data, meaning they do not move or alter the source files. They contain links to the source data.
Create a mosaic dataset for each annual collection of imagery. For example, if the collection can be grouped into six years, such as 1995, 1998, 2000, 2010, 2016, and 2020, create seven mosaic datasets—one for each year and one primary to contain all the years. Complete the following steps six times:
- Create a mosaic dataset for each year by right-clicking the geodatabase in the Catalog pane and clicking New > Mosaic Dataset, or use the Create Mosaic Dataset tool.
Choose a coordinate system appropriate for the imagery you are adding if it is not all in the same coordinate system.
- Add the imagery to each mosaic dataset using the Add Rasters To Mosaic Dataset tool.
Add the 1995 imagery to the 1995 mosaic dataset, add the 1998 imagery to the 1998 mosaic dataset, and so on.
- Check the Update Overviews parameter to build overviews for the mosaic dataset.
- Click Advanced Options and check Build Raster Pyramids and Calculate Statistics.
These options build the pyramids and statistics for all the input raster datasets if they don't exist. Alternatively, you can use the Build Pyramids And Statistics tool to compute this information separately.
- Verify that the imagery is displayed properly for each mosaic dataset.
Create the primary mosaic dataset
Create the primary mosaic dataset to contain each of the mosaic datasets you created. You can create a reference mosaic dataset, but since you will add fields and possibly modify the boundary and add additional overviews (from another web service), it's best to create a standard mosaic dataset.
- Create the primary mosaic dataset by right-clicking the geodatabase in the Catalog pane and clicking New > Mosaic Dataset, or use the Create Mosaic Dataset tool.
Choose a coordinate system appropriate for all the imagery you are adding if it is not all in the same coordinate system.
- Use the Add Rasters to Mosaic Dataset tool to add each mosaic dataset.
- Click the Raster Type drop-down arrow and click Raster Dataset.
- Click the Input drop-down arrow and click Dataset.
- Click the Input browse button and select one of the mosaic datasets.
Repeat this step until all the mosaic datasets comprising the primary mosaic dataset are listed.
Do not check the option to update overviews, since this workflow uses a web service instead of building overviews for the primary mosaic dataset.
- Click OK.
Add the Year field to the mosaic dataset
To make the mosaic dataset time aware, create the attribute field in the mosaic dataset and add the correct dates.
Add the new field to the footprint attribute table
ArcGIS Pro will be used to alter the attribute table to accomodate the different mosaic datasets.
- Add the master mosaic dataset to ArcGIS Pro.
- Right-click the Footprint layer and click Open Attribute Table.
The table contains a row for each mosaic dataset you added.
- Click the Add Field button in the Fields pane, and click in the Field Name field highlighted at the bottom of the pane.
- Type Year in the Name text box.
- Click the Type drop-down arrow and click Text.
- Click OK.
- Close the Fields pane and save the changes.
Enter the year values
In this step, you will add the year value in the attribute table for each of the added mosaic datasets representing each year.
- In the attribute table for the Footprint layer, locate the new Year field for each of the primary images.
- For each row in the table, type the year in the Year column for each corresponding mosaic dataset.
- On the Edit tab, click the Save button to save the edits. When the Save all edits option appears, click Yes.
Examine the temporal mosaic dataset
To enable time on the mosaic dataset and use the Time pane to navigate through the imagery in the mosaic dataset, complete the following steps:
- Zoom in to an area in the mosaic dataset where you can see the high-resolution imagery (not the service imagery).
- Right-click the mosaic dataset and click Properties.
- Click the Time tab.
- Check Enable time on this layer.
- Click the Time field drop-down arrow and click Year.
This is the field you created and populated.
- Click the Time step interval text box and choose View using unique times in the data.
This allows you to use the custom intervals set when you added to the mosaic dataset.
- Click the Time step interval drop-down menu and click Year.
- Click OK.
The Time tab appears.
- Click the Time tab and click the Time button to enable time.
- Use the slider to examine the imagery year by year.
You can also serve the mosaic dataset as an image service using ArcGIS Image Server or ArcGIS Image for ArcGIS Online.