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Problem: In ArCGIS Image Server, NoData values of the source rasters in an elevation service display as actual values in the image service

Description

The NoData values of the source rasters in an elevation service display as actual values in the image service. This causes the stretch applied to the elevation service display to render incorrectly.

Cause

Image Server does not currently support reading NoData values.

Solution or Workaround

The NoData parameter in the Raster Properties dialog box needs to be defined for each raster dataset prior to building overviews. The following steps outline the process involved with handling the NoData values as NoData in the image service:

  1. If the NoData value is being defined for an individual raster:

    A. Select the record corresponding to the elevation raster in the service table.

    B. Select the 'Raster Properties' button on the Service Editor toolbar.

    C. Select the 'Rasters' option on the left side of the Raster Properties window and specify the raster's NoData value in the 'No data value' parameter.

    If the NoData value is being defined for multiple rasters:

    A. Select the Image Service button > Advanced > Edit Raster Properties option.

    B. In the 'Edit Raster Properties Wizard', select the 'General properties of raster datasets or rasters' option. Click Next to proceed.

    C. Select either 'Raster dataset' if all rasters are to be defined, or 'Raster' if a subset is to be defined. With the 'Raster' option, the subset can be selected by raster ID. Click Next to proceed.

    D. Check the 'NoData value:' option and enter the desired value. Click Next to proceed.

    E. Select the 'No' radio button if no further modifications of the raster properties are desired. Click Next, and then click the Finish button.
  2. Activate the Transparency option in the service properties.

    A. Initialize the Service Properties dialog box by selecting the 'Image Service Properties' button on the Service Editor toolbar, or by right-clicking the ISDef layer and selecting 'Properties'.

    B. Select the 'Service Definition' section in the Image Service Properties dialog box.

    C. Change the Transparency parameter to 'On'.
  3. Run 'Build' with the 'Compute Output Pixels' option enabled, then proceed to define and build overviews if desired.

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