exploration vs pilotage

exploration

noun
  • The process of exploring. 

  • A physical examination of a patient. 

  • The (pre-)mining process of finding and determining commercially viable ore deposits (after prospecting), also called mineral exploration. 

  • The process of penetrating, or ranging over for purposes of (especially geographical) discovery. 

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 exploration and pilotage occurred in a corpus of books? (source: Google Ngram Viewer )