The layers within a map are 'projected-on-the-fly' if the data frame uses a coordinate system that is different then those of the layers. In certain cases, the features of an ArcIMS Service are lost after the coordinate system of the data frame is changed.
Older versions of ArcIMS (pre 9.0) use an older version of the Projection Engine. The Projection Engine identifies a coordinate system by an integer code. ArcMap uses these codes in order to make coordinate system requests on the ArcIMS server.
Therefore, the request from ArcMap may include codes that do not exist on the server, resulting in lost features.
There are two cases where the new codes cause problems when changing the coordinate system of the data frame.
- Many pre-existing coordinate systems had code changes in the ArcGIS 9.0 Projection Engine. This was done in order to conform with the latest EPSG codes.
The ArcGIS Desktop 9.0 Reprojecting ArcIMS Layers Patch addresses this case. See the Related Information section.
- ArcGIS 9.0 also includes new map projections. These map projections are not present in pre 9.0 versions of ArcIMS. The only work-around is to select a map projection that is supported.
Below is a list of the new map projections supported at 9.0:
- Robinson (ArcInfo workstation version)
- RSO (Rectified Skew Orthomorphic)
- Transverse Mercator Complex