Whenever I create an enum I give it a prefix. In this case Area. The prefix shows that they belong together and it makes it less prone to problems with duplication on copnstants.
If we don't like Area, I would propose using Fiware as prefix:

      typedef enum FiwareArea
      {
         FiwareNoArea,
         FiwareCircle,
         FiwarePolygon
      } FiwareArea;