Hydrographic Surveying
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It is the branch of surveying which deals
with any body of still or running water such as a lake, harbor, stream or
river. Hydrographic surveys are used to define shore line and under water
features.
Objects
of Hydrographic Surveying:
Hydrographic surveying are carried out for
one or more of the following activities.
- Measurement of
tides for sea coast work E.g. construction of sea defense works, harbors
etc, for the establishment of leveling datam and for reducing sounding.
- Determination
of bed depth, by soundings
- For
navigation
- Location of
rocks, sand bars, navigation light.
- Fro location
of under water works volumes of under water excavation etc.
- In connection
with irrigation and land drainage schemes.
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- Determination
of direction of current in connection with
- The location
of sewer any pipe or channel that carry waste water out falls.
- Determination
of area subject to silt and seour the eating of the place.
- Fornication
purposes.
- Measuremenment
of quantity of water and flow of water in connection of water schemes,
Power scheme and flood controls.
- Offshore
engineering and the shipping industry have continued to expand.
- Drilling rigs
(extracting oil, gas etc from deep sea) locating up to 125miles
offshore, search for resources particularly oil and gas.
- Offshore
islands are constructed of dredged material (to bring material form some
where and dump there) to support marine structure.
- Harbor depth
up to 80 is required to accommodate larger ships and tankers.
- Containerization
has become an efficient and preferred method of cargo handling.
- The demand for
recreational transportation ranges form large pleasure cruise ships to
small sail bonds.
- Cruise ships
to small sail bonds. Hydrographic surveys are made to a quire and
present data on oceans, lakes and harbors. It comprises all surveys made
for
- The
determination of shore lines, soundings (measurement of depth below the
water level) characteristics of bottoms, areas subjected to Suring and
silting, depth available for navigation and velocity as well as
characteristics of flow of water.
- The location
of lights rocks sand balls, buoys ( anything that floats on the surface
of water)
Horizontal Controls:
In an extensive survey, the primary
horizontal control is established primarily by running theodolite and tape
traverse before the triangulation station. Tthe traverse lines being run to
following the shore lines approximately. In survey of less extent the primary
horizontal control only is required and is established by running a
theodolite and tape traverse sufficiently close to shore line. For rough
work, the control may be established by running a theodolite and staid
traverse or plane table trader.
Vertical Controls:
These are based upon a series of bench
marks established near the shore line by spirit leveling and these serve for
setting and checking tide gages etc to which the sounding are referred.
The survey of the shore line of a river is
made by running a theologize and tape traverse on a shore at a convenient
distance form the edge of the water. If the river is narrow, a single
theologize and tape traverse is on one bank and both banks. Located by staid
or plane table methods.
The measurements of depths below the water
surface is called Sounding. The object of making soundings is to determine
the configuration of the bottom of the body of water. This is done by
measuring form the boat, the depth of water at various points
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