NP5011 is primarily a key to symbols and abbreviations used on Admiralty and International paper charts and leisure folios compiled by the United Kingdom Hydrographic Office (UKHO). Variations may occur on charts adopted into the Admiralty Series that were originally produced by another hydrographic office. Where these symbols and abbreviations are easily understood they are not included as examples in this title. Similarly, symbols and abbreviations shown on Electronic Chart Display and Information Systems (ECDIS) may differ from those described in this book; the key to such symbols is available on NP5012. Revised editions of NP5011 are published as necessary to show symbols which have been newly introduced and to record other developments in charting practice.