A shapefile has a related .prj file; thus, it appears to have a particular projection attached to it. Its properties, however, show the spatial reference set to Unknown.
A discrepancy between Input Locale and the Numbers settings in the Regional Options Control Panel can cause this problem. For example, if you change Decimal Symbol and the Digit Separator Symbol on the Numbers tab, without changing the Input Locale to an appropriate setting, the feature class spatial reference will be listed as Unknown.
Methods for changing the locale depends upon your operating system. Web site links for various operating systems are provided below.
Change the Input Locale setting to an appropriate location for the number separator symbols you want to use. You may have to select a number of locale settings until you find one that uses the symbol settings that you want. For example, if you want to use comma separated decimal numbers, use an European locale, such as Swedish.
For additional help, see the related article "Set the default sysDescribe how to fix Locale settigs. For example in AppServer.properties [4/18/2002]tem locale" in the link below.
Get help from ArcGIS experts
Download the Esri Support App