Why it serves a bathymetric rise?

EThese works are realised with a view to determine the depths accurately and characteristics of the Lagos bottom, rivers, ports and the oceans, besides determination of the main characteristics of the surrounding terrestrial areas.

It can include following the objectives data of tides, currents, gravity, terrestrial magnetism, and determinations of the physical and chemical properties of the water.

The primary target of the majority of the hydrographic surveyings is to obtain initial datas for the compilation of some type of cartography but also can to include the acquisition of the necessary information for products related to marine navigation and for the administration of the coastal zone, engineering or with commercial aims.

The purpose of the hydrographic surveying:

• To compile, with systematic rises in the sea, the coast, and mainland the data georeferenciados regarding:

1. The configuration of the coastline, including infrastructures done by the man that is of interest for the navigators.
2. The depth in the interest area (in particular all the dangers potentials for marine navigation and other activities).
3. The composition of the marine bottom.
4. The tides and currents.
5. The physical properties of the water column.

The collected data are due to process of form ordinate to create the data bases and to organize them of way to feed the production on thematic maps, letters nautical and other types of documentation.

A nautical letter is a graphical or electronic representation of the marine atmosphere on that we sailed, presenting/displaying the nature and the form of the coast, depths of the water, and the configuration of the ocean floor. Furthermore it gives us location of the dangers to navigation (ex a sand bank) and information of artificial aid to navigation. (ex. A marking of buoys buoy).

At present the electronic cartography has acquired a significant importance by the typical that offer. The real form of a letter can vary of one traditional letter of paper to an electronic letter.

An electronic letter is not simply a digital version of a paper letter; it very introduces a new methodology of navigation with capacities and limitations different from those from paper letters. The electronic letter has become legal equivalent of the paper letter as Organization was approved by the OMI ( The marine International).

Such letters have, like objective, (besides the security to navigation) knowledge of the atmosphere required for the underwater running, oceanographic investigation or the industrial application, such as positioning of cables, mining of the ocean floor and oil operation.

The hydrographic surveying is undergoing fundamental changes in technology of the measurement. Airborne the acoustic systems multihaz and laser now they provide cover and almost total measurement of the marine bottom with respect to previous samplings done by bathymetric profiles. The capacity to position the data with exactitude in the horizontal plane have grown enormously thanks to availability of the systems of satelite positioning, particularly when it resorts to technical differentials.