An imaginary line that connects points of equal height value eg the elevation of the land surface above or below a vertical datum, in this case of LINZ topographic mapping, this is Mean Sea Level.
Data Dictionary for contour: http://apps.linz.govt.nz/topo-data-dictionary/index.aspx?page=class-contour
This layer is a component of the Ant50 map series. This is the topographic mapping carried out at 1:50,000 scale by LINZ within the Ross Dependency, Antarctica.
Since 1923, New Zealand has maintained its right of sovereignty over the Ross Dependency, an area defined as all islands and territories south of 60 degrees south latitude and between the 160th degree of east longitude and the 150th degree of west longitude LINZ, in conjunction with the USGS, carried out mapping of the Dry Valleys area and Ross Island in the 1980s and 1990s In 2007, LINZ expanded the mapping to include the Darwin/Hatherton Glacier region of Antarctica. The purpose of this is to support science taking place in the region as part of the Latitudinal Gradient Project. The data provided is based on ALOS PRISM satellite imagery taken during the 2006/07 season and is supplied in the Darwin Glacier Lambert Conformal Conic 2000 projection. The survey work for this data was undertaken between 2007-2010.