Daymarks

In the definition of a navigational aid given above, there is no distinction between night and day. Plenty of navigational aids exist which provide guidance in daylight, but which are unlit. These are termed daymarks. A navigational aid built today would be designed to be visible both by day and by night, and would therefore be lit, at least by night. In many countries, designs specifically include brightly coloured geometrical figures – stripes, bands, squares etc – painted on rectangular, square, triangular or pyramidal boards for maximum daytime visibility. To enrich our terminology, we propose that the term daymark is used to apply to any built, unlit navigational aid, whether or not it actually bears a light, for it is clear that when a lighthouse or lightstructure is unlit, then it is also performing the role of a daymark.

	A daymark at Hill Head, near Lee-on-the-Solent, Hampshire, UK. The structure can be described as a wooden framework tower with a white horizontal band and an orange mark. It is simply a positional device. Photo: Ken Trethewey, 2003
	A much more permanent and well-known daymark in Cornwall, UK, at Gribbin Head, near St Austell. This large structure marks a prominent headland. Photo: Ken Trethewey, 2003
	A very simple daymark to indicate a fixed hazard, i.e. the rocky outcrop. Photo: Ken Trethewey, 2003

© 2003 Ken Trethewey