bird's-eye view vs viewport

bird's-eye view

noun
  • The view from directly or high above. 

  • A general overview or summary of a topic. 

viewport

noun
  • A viewing window. 

  • A typically rectangular region representing the range or area currently visible (within a window, screen, etc.). 

verb
  • To clip (an image or region) so that it fits in a viewport. 

How often have the words bird's-eye view and viewport occurred in a corpus of books? (source: Google Ngram Viewer )