Creating an elevation service when pixel values will be queried

When you create an image service definition serving elevation data that will be used by ArcGIS Image Server as the input to another process, such as orthorectification, or the data will be exported by the client, the correct pixel values will be transmitted. However, when you are viewing the image service in an application, such as ArcMap, the pixel values transmitted to the application have a display sampling method applied. By default, image service definitions set bilinear interpolation as the sampling method. Therefore, if you are using the Identify tool in ArcMap, you might not get the exact pixel value you would if you were querying the original data.

If your clients intend to use the Identify tool, there are two things that can be done—either the client can change the sampling method on the Image Service Layer Properties dialog box (on the Display tab), or when you set up the image service definition, you can change the display sampling method to nearest neighbor (described below).

步骤：

1. Add the Image Service Definition Editor toolbar to ArcMap.
2. Click the Image Service drop-down menu on the toolbar, click New Image Service, then follow the wizard to create the elevation image service definition, without terrain visualization. Add the data and accept the defaults to build service overviews and compile.
3. Click the Image Service drop-down menu and click Advanced > Build.

   After the image service definition is completely generated, it is recommended that you rebuild with the Compute output pixel properties option checked. This calculates the histogram values for the entire image service.

4. Check Compute output pixel properties and click OK.
5. Click the Image Service Properties button on the toolbar to change the default sampling method.
6. Click the Default Client Properties node.
7. Click the Sampling method drop-down arrow and click Nearest Neighbor.
8. Finally, recompile the image service before publishing it. Click the Image Service drop-down menu and click Advanced > Build.
9. Check Compile service and click OK.