DO derivative work have to be included in copyrights agreements?

two cases:

  • Suppose you create a world map for a client, then he in the future will have the need to create a new map for a portion of the world to be represented in book or other media may be with another new style , new map etc but based on the shapes and work of the originally made one ... is this considered a derivative work ? Should be included a clausole in contracts of any kind?
  • Another example imagine Game of Thrones if you make a map based on it can you sell it by your own or there are copyrights infringments?