In the dark past, it was realised that:
The seas and oceans of the world are dangerous places;
Efforts must be made to improve the safety of those who go to sea.
The all-embracing term that describes these efforts is the provision of ‘navigational aids’, or ‘aids to navigation’, as they are also known.
It could be argued that a map or a chart is an aid to navigation, and so they are – graphical aids. The first use of marine charts is not precisely known, but they must have been used from earliest times. In parallel with this graphical aid, lists of navigational aids have also been prepared, along with known hazards and instructions for their avoidance. In early English culture, these were called 'Rutters' or 'Sailing Instructions'. These have evolved today into the many books used by mariners under the heading of Nautical Almanacs or Coastal Pilots.
A GPS receiver is also an aid to navigation, albeit an electronic one, whilst a sextant is a mechanical measuring device using optics. But when we use the term, navigational aid, we are usually describing any artefacts set up, either in the sea or on land, with the assigned purpose of assisting seamen in safe navigation. These artefacts can be either lit or unlit. We are also describing artefacts that were built for other primary purposes.