Handling NoData in Image Server

[Anonymous User]

Original User: xiannian

Hi, friends,

We have problems on handling NoData in water depth when using Image Server.
The data are water depth TIFF image files. Depth values are only showing at the area where rivers/streams appear. So, majority of the image area are NoData. When the data is loaded into ArcMap, NoData areas are NoData and the return value of a pixel is NoData when Identify tool is used. The value range is reasonable, say, from 5 to 100. Refer to the first attached image, please.

The problem happenes when the same data is handled with Image Serer. The service is set to be an Elevation service. After the service is created, the problems appear. First, the display of image is not right. The NoData area is not blank as the data is TIFF format. Second, the value range, which is from -131072 to 130820, is not in the right range. Refer to the second attached image, please.

So, my questions include two: first, why the data range is not set to the right one? second, how to set the NoData area to be as it is in TIFF format?

Any help will be welcomed.

Thanks,

Xiannian

[Anonymous User]

Original User: hlzhang

It looks that you intend an 'identity' image service from DEM (i.e., AS IS of elevation values).

If so, not feasible to get it in Image Server 9.3.x. As Jeff indicated, it is known issue. In Image Server 9.3.x, only three derived images from DEM sources can be created, that is, Hillshade, Elevation Coded, Shaded Relief under Elevation catalog.

So, you need use Mosaic Dataset in ArcGIS 10 to create it (see the attached snapshot, where the surface elevation is minus 426 m, the lowest sea surface in the world).

When using Mosaic Dataset in ArcGIS 10 to create 'Identity' image service from DEM, however, two things should be paid attention to:

Firstly,  make sure that you use 'Identity Function' rather than 'Stretch Function' in the function chain;

Secondly, if the boundary of DEM images is irregular, you can 'immediately' run 'building footprint' script after loading DEM in GRID, in order to remove NoData. In this way, it usually wouldn't affect '0' values (if '0' value is the sea surface).

Of course, when DEM in TIFF used, minimum value like 0, or -200 (default is 1) should be set up properly, before runing the 'building footprint' script. However, when DEM in IMG used, be cautious (I had a feeling that some bugs exist in 64-bit ArcGIS 10 SP1).