During the brief, ice-free summer of the Beaufort Sea, thirty members of the Canadian Hydrographic Service on board the C.S.S. Hudson, are charting a sixteen km-wide shipping corridor that will permit transport of Arctic gas and oil by deep-draught tankers through the Northwest Passage. Colourful computer-animated graphics and on-location footage illustrate how navigation charts are made and how sophisticated electronics have facilitated the task of the modern-day hydrographer.