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FAQ: How does Image Server handle datum transformations?

Question

How does Image Server handle datum transformations?

Answer

The AISDatatums.txt file is the file that manages datum transformations for Image Server.

In ArcGIS Image Server 9.2, the file is located in the following path:

C:\Program Files\ESRI\Image Server\pedata

In ArcGIS Image Server 9.3, the file was moved and can be accessed from the following path:

C:\ProgramFiles\ArcGIS\ImageServer\pedata

Depending on the area of interest, this file may need to be edited on occasion. For example, if there is data in California and a service was created in GCS_NAD_1983, but the data is in GCS_NAD_1927, it is necessary to edit the AISDatums.txt file so that NAD_1927_To_NAD_1983_NADCON is above any other NAD_1927_To_NAD_1983 transformation in the text file.

The easiest way to accomplish this is to open AISDatums.txt in WordPad and move the appropriate transformation for the area of interest to the top of the list. Image Server uses the first transformation it finds in the file. If the order is incorrect, the wrong transformation will be applied.