 Navigators charted the coastline of the northern and eastern portions of New Guinea in the early 17th century and , later in the century , British Admiralty navigators named the visible mountain ranges . Most German surveying efforts had focused on coastal regions and river basins , where Germans had established plantations , leaving the interior unexplored . In late 1913 , the Imperial Colonial office appointed Detzner to lead an expedition to survey the border between the British protectorate , called Papua , and the German territory , called Kaiser @-@ Wilhelmsland , and to survey and map the interior . 
