How to
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The
first step in making a hydrographic survey is to control both horizontal and vertical.
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.
Stadia Surveying:
The distances are determined by angles there are stadia
hairs from which angles and all calculations are determined without change.
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. |
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Shore Line Surveying:
Purpose:
All irregularities in the shore line as well as the shore
details are located by means of offsets measured with a tape form the traverse lines, by staid or plane table.
The points of reference should be dearly risible form the
water and should be near enough such wing mills, flag poles etc. buoys anchored off the shore and light houses are used reference points.
The position of the high water line may be judged roughly
form deposits an marks on rocks however to locate it accurately the elev of mean high water is determined and point are located on the shore at that elevation. The line connecting these points represent high water level. |
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