Units of Measurement

Units of measurement used in past and present surveys are

For construction work: feet, inches, fractions of inches (m, mm)
For most surveys: feet, tenths, hundredths, thousandths (m, mm)
For National Geodetic Survey (NGS) control surveys: meters, 0.1, 0.01, 0.001 m

The most-used equivalents are
1 meter=39.37 in =3.2808 ft
1 rod =1 pole=1 perch=16.5ft(5.029 m)
1 engineer’s chain =100 ft =100 links (30.48 m)
1 Gunter’s chain= 66 ft (20.11 m) =100
Gunter’s links(lk)=4 rods=0.020 km

1 acre=100,000 sq (Gunter’s) links=43,560ft²= 160 rods²=10 sq (Gunter’s) chains=4046.87m²=0.4047 ha

1 rood=1011.5 m²=40 rods²

1 ha= 10,000 m²=107,639.10 ft²=2.471 acres

1 arpent=about 0.85 acre, or length of side of 1 square arpent (varies) (about 3439.1 m²)

1 statute mi=5280 ft=1609.35 m

1 mi²=640 acres (258.94 ha)
1 nautical mi (U.S.)= 6080.27 ft= 1853.248 m

1 fathom=6 ft (1.829 m)

1 cubit=18 in (0.457 m)

1 degree=0.01745 rad=60 min =3600 s
sin 1 =0.01745241
1 rad = 57.30 degree

Explain Squares or Grid Method of Contouring?

Squares or grid method is suitable for contouring of plains or gently sloping grounds.

The steps adopted are as follows: 
i) Mark square grids on the land to be surveyed. The grid size would depend on the extent of survey.
Generally a 1m x 1m grid is selected for small works and a larger grid size for large works

ii) Levels are taken at all the corners of the square and the intersection of the diagonal.

iii) Levels taken on the intersection of diagonals is used for verification of the interpolation.

vi) Contour map is plotted in the office by interpolating points of equal elevation based on the levels taken on the corners of the square.

Explain Terms Used in Contouring

Define Contour Line
A Contour line is an imaginary outline of the terrain obtained by joining its points of equal elevation. In our example of the cone, each circle is a contour line joining points of same level.

Define Contour Interval (CI)
Contour interval is the difference between the levels of consecutive contour lines on a map. The contour interval is a constant in a given map. In our example, the contour interval is 1m.

Define Horizontal Equivalent (HE)
Horizontal equivalent is the horizontal distance between two consecutive contour lines measured to the scale of the map.

Gradient
Gradient represents the ascending or descending slope of the terrain between two consecutive contour lines. The slope or gradient is usually stated in the format 1 in S, where 1 represents the vertical component of the slope and S its corresponding horizontal component measured in the same unit.

The gradient between two consecutive contour lines can also be expressed in terms of Tan Q(theta) as follows:
Tan Q (theta) = CI / HE … both measured in the same unit.

ESTIMATION METHODS OF BUILDING WORKS

The estimation of building quantities like earth work, foundation concrete, brickwork in plinth and super structure etc., can be workout by any of following two methods:

a) Long wall – short wall method

b) Centre line method.

c) Partly centre line and short wall method.

a) Long wall-short wall method:

In this method, the wall along the length of room is considered to be long wall while the wall perpendicular to long wall is said to be short wall. To get the length of long wall or short wall, calculate first the centre line lengths of individual walls. Then the length of long wall, (out to out) may be calculated after adding half breadth at each end to its centre line length. Thus the length of short wall measured into in and may be found by deducting half breadth from its centre line length at each end. The length of long wall usually decreases from earth work to brick work in super structure while the short wall increases. These lengths are multiplied by breadth and depth to get quantities.

b) Centre line method:

This method is suitable for walls of similar cross sections. Here the total centre line length is multiplied by breadth and depth of respective item to get the total quantity at a time. When cross walls or partitions or verandah walls join with main wall, the centre line length gets reduced by half of breadth for each junction. Such junction or joints are studied carefully while calculating total centre line length. The estimates prepared by this method are most accurate and quick.

c) Partly centre line and partly cross wall method:

This method is adopted when external (i.e., around the building) wall is of one thickness and the internal walls having different thicknesses. In such cases, centre line method is applied to external walls and long wall-short wall method is used to internal walls. This method suits for different thicknesses walls and different level of foundations. Because of this reason, all Engineering departments are practicing this method.

TYPES OF DEEP FOUNDATION

Deep foundations are required to carry loads from a structure through weak compressible soils or fills on to stronger and less compressible soils or rocks at depth, or for functional reasons. These foundations are those founding too deeply below the finished ground surface for their base bearing capacity to be affected by surface conditions, this is usually at depths >3 m below finished ground level. Deep foundations can be used to transfer the loading to a deeper, more competent strata at depth if unsuitable soils are present near the surface.

The types of deep foundations in general use are as follows:

1) Basements

2) Buoyancy rafts (hollow box foundations)

3) Caissons

4) Cylinders

5) Shaft foundations

6) Piles

Basement foundations:

These are hollow substructures designed to provide working or storage space below ground level. The structural design is governed by their functional requirements rather than from considerations of the most efficient method of resisting external earth and hydrostatic pressures. They are constructed in place in open excavations.

Buoyancy rafts (hollow box foundations)

Buoyancy rafts are hollow substructures designed to provide a buoyant or semi-buoyant substructure beneath which the net loading on the soil is reduced to the desired low intensity. Buoyancy rafts can be designed to be sunk as caissons, they can also be constructed in place in open excavations.

Caissons foundations:

Caissons are hollow substructures designed to be constructed on or near the surface and then sunk as a single unit to their required level.

Cylinders:

Cylinders are small single-cell caissons.

Shaft foundations:

Shaft foundations are constructed within deep excavations supported by lining constructed in place and subsequently filled with concrete or other pre-fabricated load-bearing units.

Pile foundations:

Pile foundations are relatively long and slender members constructed by driving preformed units to the desired founding level, or by driving or drilling-in tubes to the required depth – the tubes being filled with concrete before or during withdrawal or by drilling unlined or wholly or partly lined boreholes which are then filled with concrete.

Types of Chains and Tapes in Civil Surveying Engineering

Types of Surveying Chains: Following are the various types of chain in common use: Metric chains Steel band or Band chain Gunter's chain or surveyors chain Engineers chain Revenue chain 1. Metric Chain: Metric chains are made in lengths 20m and 30m. Tallies are fixed at every five-meter length and brass rings are provided at every meter length except where tallies are attached.

2. Gunter’s Chain Length = 66’ (22 yards), No of links = 100, Each link = .66’ Used for measuring distances in miles or furlongs (220 yards), acres (Area). 3. Engineer’s Chain Length = 100’, No of links = 100, Each link = 1’ Used in all Engineering Surveys. 4. Revenue Chain Length = 33’, No of links = 16 Commonly used for measuring fields in cadastral Survey. Types of Measuring Tapes in Surveying 1. Cloth or linen tape Used for subsidiary measurements Very light, easy to handle May effect by moisture 2. Metric steel tape Made of steel Outer end is provided with a ring for holding 3. Invar tape Used for high precision work Made of alloy steel 4. Synthetic tape Made of glass fiber with PVC coating These are used for short measurements