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Time on a ship's clocks and in a ship's log had to be stated along with a "zone description", which was the number of hours to be added to zone time to obtain GMT, hence zero in the Greenwich time zone, with negative numbers from −1 to −12 for time zones to the east and positive numbers from +1 to +12 to the west (hours, minutes, and ...
Since the length of a nautical mile, for practical purposes, is equivalent to about a minute of latitude, a distance in nautical miles on a chart can easily be measured by using dividers and the latitude scales on the sides of the chart. Recent British Admiralty charts have a latitude scale down the middle to make this even easier. [10]
If present, a dagger (†) indicates the usage of a nautical time zone letter outside of the standard geographic definition of that time zone. Some zones that are north/south of each other in the mid-Pacific differ by 24 hours in time – they have the same time of day but dates that are one day apart. The two extreme time zones on Earth (both ...
To calculate the rate at an intermediate tide between neap and spring, interpolation is required. Traditionally this has been done using a "calculation of rates" chart found inside tidal atlases. [5] An alternative to a tidal atlas is a nautical chart that provides tidal diamonds.
[8]: 10 [9] The most common chart size was early established as the "Double-elephant", about 39 X 25.5 inches, and this has continued to be the case. [10] Chart design gradually simplified over the years, with less detail on land, focusing on features visible to the mariner. Contours were increasingly used for hills instead of hatching.
Fundamentals, includes an overview of the types and phases of marine navigation and the organizations which support and regulate it. It includes chapters relating to the structure, use and limitations of nautical charts; chart datums and their importance; and other material of a basic nature. Part II
Initially, the log-line was not knotted and sailors measured the length directly on the line. With the introduction of the nautical mile as a standard unit of measure at sea in the 15th century, they began to mark the line at equal intervals proportional to the nautical mile and to the time interval used for measurement. Initially, the markings ...
OpenSeaMap is a software project collecting freely usable nautical information and geospatial data to create a worldwide nautical chart. This chart is available on the OpenSeaMap website, and can also be downloaded for use as an electronic chart for offline applications. [1] The project is part of OpenStreetMap. OpenSeaMap is part of the ...