About the service table
The service table acts as a catalog of the raster datasets that make up an image service definition. Each raster dataset included in an image service definition is referenced by one record in the service table. The service table is stored as part of the footprint shapefile within an image service definition, with each raster dataset being represented by a footprint. The service table includes a number of fields that provide information about the raster dataset. Some fields in the service table control how raster datasets should participate in the image service definition, such as the display range, status information, and different metadata.
The service table contains the following fields:
- Raster Source—A link to the raster process definition (.RPDef) file, which defines the raster dataset and links to the individual rasters.
- Raster Type—The type of the raster dataset, such as QuickBird or Landsat 1G. This is defined when the raster data is added to the image service definition.
- Raster Name—A name given to each raster dataset defined in the .RPDef file. This name is generally used to enable linking of records in the service table to other attribute tables containing metadata. The raster name need not be unique within the service table. While using the lock image mosaic method, the raster name can be used as an image ID.
- Raster ID—A unique identifier given to each instance of a raster dataset. The value is generated based on the date and time the raster dataset is added to the image service definition. It is used internally for indexing. For example, the seamline polygon is linked to the raster based on the raster ID. The raster ID can also be used as an image ID when using the lock image mosaic method.
- Low and high pixel sizes—These values are extracted from the raster process definition and used to define the range of pixel sizes that the raster dataset contains. For example, a raster dataset that contains a pyramid (or internal overview) will have a range of pixel sizes. For raster datasets with no pyramids, the low and high pixel sizes may be the same value. The pixel size is always defined in meters irrespective of the spatial reference system of the image service or the raster dataset itself.
- Minimum and maximum pixel sizes—When a client makes a request for imagery covering an area of interest, the pixel size of the request is computed and only raster datasets that have a minimum and maximum that bound this value are considered. The minimum and maximum pixel sizes for a raster dataset are computed during the build process and depend on the overlapping raster datasets.
- DispOrder—Overrides the ordering of raster datasets while mosaicking to enable the selection of the raster dataset that should be displayed on top. If the value is 0, the order of the raster dataset is defined on the Default Client Properties node on the Image Service Properties dialog box. If the value is set to a number below 0, the raster is always displayed on top with a high priority. This can be used, for example, to display a lower-resolution raster with a specified footprint to cover areas that should not be seen at high resolutions. The lower the value, the higher the display order. If the value is set above 1, the raster dataset is always displayed as a background when no other raster exists covering the requested area. This can be used to provide a background image.
- Status ID—Status ID of the raster dataset within the image service definition. This is a numeric field. A value of 0 indicates no error; values between 1 and 999 indicate warnings. Values of 1000 or greater indicate errors. The footprints can be symbolized, or selection sets can be made utilizing this value to identify possible problems or errors.
- Status Message—Text that provides information on the error or warning defined by the status ID.
Additional fields can be defined in the service table or linked. Typically metadata fields, such as date, cloud cover, or quality of the raster dataset, are defined for raster datasets. When such metadata fields are defined, these fields can be used in conjunction with the By Attribute mosaic method to enable a client application to order the imagery as required. Other metadata fields can also be added to enable simplified management of the large number of raster datasets that can exist within an image service definition.
Learn about working with the service table
Altering service table fields
The fields defined in the service table are controlled using the Field Properties node on the Image Service Properties dialog box. The Field Properties node can be used to add and remove fields and control how fields are displayed. Additionally, if the fields are defined using field properties, metadata can be extracted from the raster process definitions when the image service definition is built.