a) Sounding

• The process of determining depth below water surface is called as sounding.
• The step before undergoing sounding is determining the mean sea level.
• Depth of Sounding is referred to the water level at the time it is made.
• The reduced level of any point of a water body is determined by subtracting the sounding from mean sea level, which it is analogous to levelling.

• A number of benchmarks (B.M.) are established at frequent intervals along the shorelines, and gauges are set on them

  Purpose of sounding

1. Preparation of accurate charts for navigation.

2. Determination of the quantities of the material to be filled.

3. Obtaining information for design of breakwaters, sea wells etc.

4. Material that to be dredged has to be determined early to facilitate easy movement in project without any confusion.

5. Material dredging should also accompany where filling has to be done. Material dumping is also measured

b)Pantograph

• A pantograph is a mechanical linkage connected in a manner based on parallelograms so that the movement of one pen, in tracing an image, produces identical movements in a second pen.

• If a line drawing is traced by the first point, an identical, enlarged, or miniaturized copy will be drawn by a pen fixed to the other.

• Using the same principle, different kinds of pantographs are used for other forms of duplication in areas such as sculpture, minting, engraving and milling.

• Because of the shape of the original device, a pantograph also refers to a kind of structure that can compress or extend like an accordion, forming a characteristic rhomboidal pattern.

• This can be found in extension arms for wall- mounted mirrors, temporary fences, scissor lifts, and other scissor mechanisms such as the pantograph used on electric locomotives and trams.

USES

1.Drafting

The original pantograph use of the was for copying and scaling line drawings. Modern versions are sold as toys.

2.Sculpture and minting

In sculpture, a three-dimensional version of the pantograph was used, usually a large boom connected to a fixed point at one end, bearing two rotating pointing needles at arbitrary points along this boom. By adjusting the needles different enlargement or reduction ratios can be achieved.

3.Other uses

Perhaps the pantograph that is most familiar to the general public is the extension arm of an adjustable wall-mounted mirror. The device which maintains electrical contact with the contact wire and transfers power from the wire to the traction unit, used in electric locomotives and trams, is also called a "pantograph".