navigation vs pilotage

navigation

noun
  • The theory, practice and technology of charting a course for a ship, aircraft or spaceship or (colloquially) road vehicle. 

  • A canal. 

  • Traffic or travel by vessel, especially commercial shipping. 

pilotage

noun
  • The use of landmarks to guide a vessel or aircraft to its destination. 

  • The occupation of a pilot. 

  • The fee paid to a pilot. 

How often have the words navigation and pilotage occurred in a corpus of books? (source: Google Ngram Viewer )