A colleague recently pointed me to an Environmental Systems Research Institute, Inc. (ESRI) podcast entitled “Best Practices: Defining Projection Information for ArcIMS Map Services” [MP3, 4.12 MB]. For anyone who has struggled with projections in ArcIMS, this is worth a listen.
Because ArcIMS web services, or any web mapping service for that matter, are typically accessed through a web application, some folks may not see the value of adding projection information to their services. This is something I wrestled with quite a bit back when I was the Web Mapping Administrator for the Wisconsin DNR a few years ago.
Adding projection information is critical if you want to allow ArcGIS desktop users to connect to your service, and integrate your data with services from other sources. Adding projection info to your web services is not only a good best practice habit to follow, it may save you hassles down the road.