pilotage vs seamanship

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. 

seamanship

noun
  • Skill in, and knowledge of, the work of navigating, maintaining, and operating a vessel at sea. 

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