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CHS is a world leader in the adoption of hydrographic survey technology, as well as in research and development. With responsibility for charting the world's longest coastline (243,792 kilometres) as well as 6.55 million square kilometres of continental shelf and territorial waters (second largest in the world), including extensive inland waterways such as the St. Lawrence Seaway, CHS ...
This is an average of lowest low waters taken over a fixed period of tidal predictions, as opposed to actual observations. This is the datum used for coastal charts published by the Canadian Hydrographic Service, [11] with the average taken from the lowest tides, one from each 19 year period of tidal predictions. [12]
Tide tables, sometimes called tide charts, are used for tidal prediction and show the daily times and levels of high and low tides, usually for a particular location. [1] Tide heights at intermediate times (between high and low water) can be approximated by using the rule of twelfths or more accurately calculated by using a published tidal ...
Nautical charts are based on hydrographic surveys and bathymetric surveys. As surveying is laborious and time-consuming, hydrographic data for many areas of sea may be dated and are sometimes unreliable. Depths are measured in a variety of ways. Historically the sounding line was used.
In the development of hydrographic services, shipping organizations played a part, but the major players were the naval powers. Recognizing hydrographic information was a military advantage these naval organizations, usually under the direction of a "Hydrographer," utilized the expertise of naval officers in collecting hydrographic data that was incorporated into the navy's collection.
A Standard port is a port whose tidal predictions are directly given in the Tide tables. [1] Tide predictions for standard ports are based on continuous observation of tide over a period of at least one year. These predictions are given in feet or meters, with respect to the chart datum for average meteorological conditions. [2]
Tidal atlases may provide additional information for areas such as estuaries where it important to calculate tides away from the ports. Such information may include co-tidal range information [3] and time differences. [4] To calculate the rate at an intermediate tide between neap and spring, interpolation is required.
A main product of the VORF project was the gridded vertical correction files which deliver the capability to transfer heights and depths from one vertical reference system to another, "allowing the direct use of depth data from surveys which is referred to a WGS84 compatible datum rather than Chart Datum and thus enabling Hydrographic surveyors to survey without the need to measure tides".