There are two groups of properties for a mosaic dataset: General and Default. The general properties are similar to those you find for all raster datasets, such as the data source, extent, cell sizes, and bit depth. The default properties are specific to the mosaic dataset and include all the nonraster dataset-specific information. These properties affect how the mosaicked image will be presented to the user (or client) and how they might interact with it. The product definition can be modified on the General tab.
Any properties set on the mosaic layer in the Contents pane will only apply to the layer and are not stored with the mosaic dataset, such as the band combination or mosaic method. Therefore, 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.
You can access the Mosaic Dataset Properties dialog box via the Catalog pane by right-clicking the mosaic dataset and clicking Properties. Here, you can make modifications to these properties. You can edit the values in the dialog box by clicking the value next to the property. You will either be able to type in a different value or make a selection from a list. You can also use the Set Mosaic Dataset Properties tool to modify the properties.
The properties on the Default tab can also impact the performance of the server or image service if the mosaic dataset is published. When publishing a mosaic dataset using ArcGIS Server, the server administrator can modify some of these properties as part of the settings on the image service; however, they will not be able to exceed the maximums you have set. For example, if you limit the allowed mosaic methods to only three of the methods, the administrator will not be able to add a fourth method. Or, if you set the maximum number of downloadable items, they can reduce the number but not increase this number. If you change the properties to exceed or limit a value, such as the Maximum Size Of Requests, you need to completely republish the mosaic dataset. If you restart the image service, the changed properties in the mosaic dataset will not be picked up.
- Maximum Size Of Requests—This property only applies when the mosaic dataset is published and accessed as an image service, the maximum number of rows and columns each time a mosaicked image is generated. By increasing these numbers, you will be increasing the time it takes to process the mosaicked image. However, you may want to increase these numbers if you are printing very large, high-resolution plots. By making these numbers too small, a mosaicked image may not display. For example, if you changed the numbers to 10, then the display window could only be 10 pixels or smaller in dimension to display an image.
- Allowed Compression Methods—Defines the method of compression used to transmit the mosaicked image from the server to the client. This property affects an image service generated from the mosaic dataset. If accessing the image service over an LAN, large data volumes do not cause a problem. However, when working over slower connections on the Internet, it would be better to apply a compression to the imagery before transmission. This compression reduces the size of transmitted imagery but puts an additional load on the server to compress the data first. This can be altered by the client.
- None—No compression is applied to the imagery, which provides the highest quality but results in the maximum volume of data transfer across the network.
- LZ77—An efficient lossless compression method recommended for imagery with similar pixel values (discrete data), such as scanned maps or results of classifications.
- JPEG—An efficient compression method that can often compress imagery by about three to eight times with little degradation of the image quality. When choosing the JPEG method, you can also edit the quality by typing a value from 0 to 100. A value of 80 tends to retain image quality while providing approximately 8x compression.
- LERC—An efficient lossy compression method recommended for data with a large pixel depth, such as float, 32-bit, 16-bit, or 12-bit data. When choosing this method, you need to specify the quality value, which represents the maximum error value that is applicable per pixel (not an average for the image). This value is specified in the units of the mosaic dataset. For example, if the error is 10 centimeters and the mosaic dataset is in meters, enter 0.1.
LERC compresses better (5 to 10 times) and faster (5 to 10 times) than LZ77 for float data and is better with integer data. When using integer data, and the error limit specified is 0.99 or less, LERC behaves as a lossless compression.
Default Resampling Method—Defines the default sampling method of the pixels, which are sampled to match the resolution of the user's display (or client request if published). The use or input of the data will impact the method you choose. This is also a property that is set on the mosaic dataset layer (or image service layer) and the user can change the setting on their layer—which will not change the mosaic dataset's default.
More accurate radiometry values are obtained using nearest neighbor sampling. This is generally faster but can result in jagged edges of features. Bilinear interpolation provides smoother images but can result in some smoothing of the image. Bilinear is recommended for continuous raster data. Cubic convolution is geometrically more accurate but slightly slower than bilinear interpolation. Majority is best applied to discrete data.
- Maximum Number Of Rasters Per Mosaic—Prevents the server from mosaicking an unreasonably large number of rasters if, for example, the client zooms in to an overview scale in a nonoptimized image service dataset that has no overview tiles generated. The default is 20.
- Cell Size Tolerance Factor—Used for controlling how mosaic dataset items with differing pixel sizes are grouped together for some operations, such as mosaicking or seamline generation. A factor of 0.1 means that all the LowPS values that are 10 percent larger than the lowest pixel size are considered to be the same. This value must be greater than or equal to 0.0. The results can be viewed in the Levels table (to access, right-click the mosaic dataset in the table of contents and click Open > Levels Table).
- Allowed Mosaic Methods—Defines the order of the rasters that are mosaicked together to create the image. You can choose one or more mosaic methods and which one will be the default. The user is able to choose from the methods you select.
- 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.
- Default Sorting Order—Controls the expected ordering of the images defined by the mosaic methods. Ascending will order the images as expected. Descending will reverse the order. For example, if the mosaic method is Closest To Center and Descending is chosen, then the image furthest from the center will be displayed.
- Default Mosaic Operator—Allows you to define how to resolve the overlapping cells, such as
choosing a blending operation.
- 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 along the edge of each raster dataset in the mosaicked image. By default, the edge is defined by the footprint or the seamline for each raster.
- Sum—The overlapping areas will contain the total cell values from all the overlapping cells.
Blend Width—Defines the distance in pixels (at the display scale) used by the Blend mosaic operator.
This value will be divided in half across the edge; therefore, if the value is 40, then 20 pixels will be blended on the inside of the footprint, and 20 pixels will be blended on the outside of the footprint.
If seamlines are present, a blending width and type can be defined for each seamline in the seamline table, thereby overriding this value.
- Viewpoint Settings—When the Closest to Viewpoint mosaic method is used, these settings will be applied:
- Viewpoint x and y spacing—Defines an offset that is used to calculate where the center of the area of interest (display view) is when you click an arrow button on the Viewpoint dialog box. These values are calculated in the units of the spatial reference system of the mosaic dataset.
- Always Clip The Raster To Its Footprint—You can choose whether to limit the extent of each raster to its footprint.
- Footprints May Contain NoData—You can choose if the NoData is a valid pixel value. If Yes, then if the mosaic method uses rasters that contain NoData, the mosaicked image will contain NoData values (and the application will not search for an overlapping raster that contains different pixel values). If No, then the application will try to find values to fill in the NoData using overlapping rasters.
- Always Clip The Mosaic Dataset To Its Boundary—You can choose to limit the image extent to the geometry of the boundary or to the extent of the boundary. When set to Yes, it limits the image extent to the geometry of the boundary. When set to No, it clips the image extent to the extent of the boundary.
- Apply Color Correction—If there is a color correction method in place for the mosaic dataset, you can choose to apply it when using the Closest to Viewpoint mosaic method.
- Minimum Pixel Contribution—You can choose the tolerance for the minimum pixel contribution. This defines the minimum number of pixels needed within the area of interest in order for a mosaic dataset item to be considered a part of that area. The default value is one pixel. A large value may decrease the likelihood of having an overlapping item being part of the area of interest; this may cause some areas of your mosaic dataset to be empty. This property is only valid when Always Clip The Raster To Its Footprint is set to Yes and Footprints May Contain NoData is set to No. This property is only helpful when you have multiple overlapping rasters in your mosaic dataset.
- Raster Metadata Level—Defines how much metadata will be transmitted from the server to the client. This can affect the transmission time when there is a lot of metadata to transmit; therefore, you may choose to limit it. The options are
- Full—The basic raster dataset information and the function chain's details will be transmitted. This is the default.
- Basic—The raster dataset level of information will be transmitted, such as the columns and rows, cell size, and spatial reference information.
- None—No metadata will be transmitted.
- Maximum Number Of Records Returned Per Request—Limits the requested number of records that will be returned by the server when viewing the mosaic dataset as a published image service.
- Allowed Fields—Defines which fields from the attribute table will be visible to the client when the mosaic dataset is served.
Time—If the mosaic dataset contains attribute fields that define time, you can create a mosaic dataset that will automatically be time aware, meaning the time properties in the layer will be defined by default. You can define the field for the start time and end time and the time format. It is recommended that you store time values in a date field; however, string and numeric fields are also supported.
- Maximum number of items downloadable per request—Limits the number of rasters that a client can download from an image service. You may want to set this to 0 if you do not want a client to download any rasters from within your mosaic dataset. Optionally, this value can affect the load. You may want to adjust this number depending on how you want clients to use their image services.
- Maximum Download Size Per Request—This is the total number of megabytes that can be downloaded at one time.