ArcGIS Help - 1. Importing MrSID files

• Open ArcMap and ArcCatalog.
• Make sure the two files, which have the same filename, but different extensions (sid, sdw) are located in the same directory. To make things more confusing, the sdw file will show up nowhere in ArcGIS, you still need it!
• Open ArcCatalog and work your way to the directory containing your data. Select the file you would like to import. Drag it into ArcMap. The image will appear on your map, however, ArcMap does know very little about the coordinate system, projection and length units of your image, which we will set next.

• In ArcMap select the imported image in the Display window. Go to View > Data Frame Properties, select the Coordinate System tab. Select your coordinate system. In most cases this will be State Plane 1983 - feet. Go to Predefined > Projected Coordinate Systems > State Plane > NAD 1983 (feet) > NAD 1983 Connecticut FIPS 0600 (feet). Click OK and go back to your map. To check whether the coordinate system is correct you can import a shapefile onto your image.

• The map units are set incorrectly. Most likely you mixed up meters and feet. The map units are most likely in feet (good ol’ engineering unit). Your display units may be meters, miles, or whatever. How to set these check out: Setting Map and Display Units.
• I have the proper projections and units, but my data won't print onto the image. Are you sure that you have the proper world file (*.sdw) loaded?  Make sure that the file name matches the name of image file exactly, except for the extension.
• I load more than one image and they plot right on top of each other.  I get an error message telling my that one or more layers are missing spatial information...  Probably the same problem:  the program can't find the proper world files.

• When downloading MrSID images from the Hartford MDC: the filenames of the worl dfiles do not match the image files.  Check them carefully, especially the last letter before the extension.  Images are named ...s.sid, world files are named ...sw.sdw.