Understanding and predicting coastal change and associated sea level rise are crucial issues in coastal planning and management. Any data which increase the understanding of the long term behaviour of the natural environment are particularly important. Tidal lines, as indicated on Ordnance Survey maps, have been used and have the potential for the geomorphological analysis of changes in beach width and possibly as indicators of sea level rise and beach erosion. Tidal lines represent clearly resurveyed, temporally and spatially transient features which predate aerial photography as a potential source of evidence of coastal change. However, any use of these features requires an understanding of the reliability, repeatability and practicality of trying to map an ambiguous feature in the field. This research principally deals with tidal line definition, data capture and the practice of the ground survey mapping of tidal lines on the Ordnance Survey maps of England and Wales from 1868 until the 1960s.