Dunnose is a cape on the Isle of Wight in the English Channel. The headland is visible from well out to sea, and is used in navigation. It has twice been used as the base point for a triangulation of Great Britain. The line of accurately surveyed points running north from Dunnose to Clifton in Yorkshire provide the basis for triangulation to determine the positions of all other locations in Britain.

SM UB-81 was a German Type UB III submarine or U-boat in the German Imperial Navy during World War I. She was commissioned into the German Imperial Navy on 18 September 1917 as SM UB-81.