This driver reads Idrisi vector files with .vct extension. The driver recognized point, lines and polygons geometries.
For geographical referencing identification, the .vdc file contains information that points to a file that holds the geographic reference details. Those files uses extension REF and resides in the same folder as the RST image or more likely in the Idrisi installation folders.
Therefore the presence or absence of the Idrisi software in the running operation system will determine the way that this driver will work. By setting the environment variable IDRISIDIR pointing to the Idrisi main installation folder will enable GDAL to find more detailed information about geographical reference and projection in the REF files.
Note that the driver recognizes the name convention used in Idrisi for UTM and State Plane geographic reference so it doesn't need to access the REF files. That is the case for RDC file that specify "utm-30n" or "spc87ma1" in the "ref. system" field. Note that exporting to RST in any other geographical reference system will generate a suggested REF content in the comment section of the RDC file.
Starting with OGR 1.10, the driver can retrieve attributes from .ADC / .AVL ASCII files.