Default map definitions are kept in special dictionaries named "${DDSROOT}/src/lib/dds3/format.map.dds". They are built into DDS and do not (normally) appear in the data Dictionary. However, when any get used they are copied into the mapped data Dictionary. This provides a comprehensive history of how processing has changed the binary data.

Dictionary      Format
--------------  ---------------------------------
usp.map.dds     usp
segy.map.dds    segy, su 
segy1.map.dds   segy Rev. 1
asp.map.dds     Generic DDS (asp, sep, cube, ...)
    

Default mappings are adequate for most, but not all, field conversions. The end user should understand what the defaults are, and override them as needed. Application programs or users may override default map definitions. This is done by adding them to the command line or par file Definitions.

Alternatively, the user can take one of these mapping Dictionaries and modify it for specific purposes. Then to get DDS to use the modified mappings, define "DDS_PATH" (or "dds_path3") to point to the directory containing the modified Dictionary. This can either be an environmental variable or a command line Definition. Multiple paths, delimited by white space, may be defined. The first Dictionary in "DDS_PATH" that matches the new format name is used to define the mappings, otherwise internal default mappings are used.

The end user may provide a mapping Dictionary for custom format. In this case just create a Dictionary with the name, "format.map.dds" and add all the mapping Definitions that are needed.