encoding utf-8
layout clean

  # line survey  
  code metapost
    def l_survey_cave_SKBB (expr P) =
      T:=identity;
      pickup PenC;
      thdraw P;
    enddef;
  endcode
  
  symbol-set SKBB
  map-header 0 0 off
  sketches on
  color map-fg [100 100 80]
  
endlayout
