- The hydrographer of the navy publishes it.
- It is used in planning deep sea voyages.
- Contains notes on meteorological factors affecting the passage.
- Guides a mariner to follow the best passage in a particular month through a particular stretch.
- It is a unique admiralty publication, in which sailing vessels are dealt with seperately.
- In passage planning both the asd and opw. Are valuable publications to refer to.
- While asd is generally required for coastal navigation the opw. Is required for ocean navigation.
- It is divided into 4 parts:
PART 1: Power Driven Vessels, Chapter 1 To 8.
Wind, Weather, Swell, current, Ice routes
PART 2: Sailing Vessels, Chapter 9 To 11.
PART 3: A Comprehensive General Index.
PART 4: Charts And Diagrammes.
- The book gives a number of illustrative charts and diagrammes showing principal routes between key places to guide a mariner in general.
- Additionally following charts are found.
- World climatic charts. (jan. – july.)
- Tracks followed by sailing and auxillary powered vessels.
- World ocean currents.
- Loadline rules, zones, areas and seasonal periods.
- OPW is KEPT UPTO DATE BY A PERIODICAL SUPPLIMENT.