The mosaicked image displayed from a mosaic dataset can be created from a number of input rasters that are often overlapping. The mosaic method defines how the mosaicked image is created from these input rasters. For example, when using the By Attribute method, the values in an attribute field are used to sort the images, and when using Closest to Center, the image closest to the center of the display is positioned as the top image in the mosaic. Additionally, the mosaic operator allows you to define how to resolve the overlapping cells, such as choosing a blending operation.
When you're viewing the mosaic dataset as a data source and not modifying it for the benefit of others, change the mosaic method from the Image layer. This way, you only impact your display and do not permanently impact others when viewing or accessing the mosaic dataset.
The mosaic methods are defined as part of the mosaic dataset properties, but all may not be available. The mosaic methods include the following:
- Closest to Center—Enables rasters to be sorted based on the ZOrder, then PixelSize, and then by a default order where rasters that have their centers closest to the view center are placed on top.
- Closest to Nadir—Enables rasters to be sorted by the ZOrder, then PixelSize, and then by distance between the nadir position and view center. This is similar to the Closest to Center method but uses the nadir point to a raster, which may be different than the center, especially for oblique imagery.
- Closest to Viewpoint—Orders rasters based on the ZOrder, then PixelSize, and then by a user-defined location and nadir location for the rasters using the Viewpoint tool.
- By Attribute—Enables raster ordering based on the ZOrder, then PixelSize, and then by the defined metadata attribute and its difference from a base value.
- North-West—Enables raster ordering by the ZOrder, then PixelSize, and then by the shortest distance between the center of a raster and the northwest position.
- Seamline—Cuts the raster using the predefined seamline shape for each raster, using optional feathering along the seams, and orders images based on the ZOrder and then the SOrder fields in the attribute table.
- Lock Raster—Enables a user to lock the display of single or multiple rasters based on the ObjectID.
- None—Orders rasters based on the order (ObjectID) in the mosaic dataset attribute table.
When using a date field with the By Attribute mosaic method, the base value must be entered using one of the following:
- yyyy/MM/dd HH:mm:ss.s
- yyyy/MM/dd HH:mm:ss
- yyyy/MM/dd HH:mm
- yyyy/MM/dd HH
To use the Closest to Viewpoint mosaic method, you need to add the Viewpoint controller to your application. To do this, see Using the Viewpoint window.
The mosaic operators include the following:
- First—The overlapping areas will contain the cells from the first raster dataset listed in the source.
- Last—The overlapping areas will contain the cells from the last raster dataset listed in the source.
- Min—The overlapping areas will contain the minimum cell values from all the overlapping cells.
- Max—The overlapping areas will contain the maximum cell values from all the overlapping cells.
- Mean—The overlapping areas will contain the mean cell values from all the overlapping cells.
- Blend—The overlapping areas will be a blend of the cell values that overlap; this blend value relies on an algorithm that is weight based and dependent on the distance from the cells to the edge within the overlapping area.
- Sum—The overlapping areas will contain the total sum of the cell values from all the overlapping cells.
The Reset button on the Mosaic tab will change the mosaic method settings back to their defaults.
Generally, the mosaicked image is created using the following process:
- A spatial query defines the potential images.
- The current scale is compared with the minimum and maximum pixel values of the potential images.
- The qualified images are selected and sorted according to the mosaic method (the sorting order can be ascending or descending).
- The overlapping area is resolved by the mosaic operator.
- In ArcMap, expand the mosaic dataset layer in the table of contents, right-click the Image layer, then click
In ArcGlobe, right-click the mosaic dataset layer and click Properties.
- Click the Mosaic tab.
- Click the Mosaic Method drop-down arrow and choose a method.
- If you choose By Attribute, you can specify a field and base value.
- If you choose Lock Raster, you can specify a raster ID value to which the mosaic dataset will be locked.
- Optionally, uncheck Sort Ascending.
This reverses the ordering method.
- Optionally, click the Mosaic Ordering drop-down arrow and choose a different ordering method.