These paths specify the default location of image correlation data.
Correlation files store data about an image insertion point, scale, rotation, and density. Correlation paths can specify a folder on a local or network drive or a location on the Internet. The read path specifies where AutoCAD Raster Design toolset searches when loading correlation information. The write path specifies where AutoCAD Raster Design toolset puts correlation information when exporting images.
Previous versions of AutoCAD Raster Design toolset (CAD Overlay GSX and ESP) created resource files to store information about an image. AutoCAD Raster Design toolset and CAD Overlay versions 7.5 and above store this information in the drawing file, and create resource files only when you export an image. For more information, see Exporting Images. If you insert an image with an associated resource file into another drawing, then AutoCAD Raster Design toolset incorporates the correlation information from the resource file.
When you insert an image, AutoCAD Raster Design toolset looks in the read path to see if a resource file or world file is associated with the image. If so, you can select this file as the source of correlation information. If you leave the read path blank, AutoCAD Raster Design toolset searches only the folder where the image was stored.