Most comics artist-authors will agree that our OCs are all projections of some part of ourselves. In Mr. Watterson's case, while Calvin/Hobbes were the channel to his inner child's self, Calvin's dad became the cathartic projection of his jaded, kvetching adult self. (It's a theory).
It’s a little of both. Calvin’s Dad has the same job as Watterson’s dad (patent attorney) and the camping trips were from memories of his dad, while Watterson identifies more with Dad than with Calvin.