TAPES Cloth or Linen Tape:

Used for taking subsidiary measurements, such as offset. It is very lightand handy. It is easily affected by humidity. If wet it shrinks. It stretcheseasily and likely to twist.

Metric Woven Metallic Tape:They are available in 2, 10, 30, and 50 meters. The tape is made of yarnand metal wire. A metal ring is attached to the outer end of tapes. Thelength of the tape includes the metal ring. At every centimeter a blackline 8 to 10 mm in height is drown. Every 5 centimeters is marked with anarrow in black. Every decimeter and meter is marked with a back lineextending over the full width of the tape/ the graduation marks at everydecimeter and meter are numbered with black and red figures,respectively.

Metric Steel Tape:Tape is available in 1, 2, 10, 30, and 50 meters. The tape is of steel orstainless steel. The outer end is provided with a ring. The length of thetape includes the metal ring. The tape is marked with a line at every fivemillimeters, centimeters, decimeters, and meter. Every decimeter andmeter shall be marked with Hindu Arabic numerals in bold. When thebutton release devised is pressed, the tape automatically rewind in to thecase.

Invar Tape:For highest precision work the invar tape in used. It is made of an alloy ofsteel and nickel (36%). It is 6 mm wide and may be obtained in length of30m and 100m. It is not calibrated through its length but has terminallines. Each terminal division has ten 1 mm division. It is very expensive.

Synthetic Tape:The tapes are manufactured of glass fiber having PVC coating. They aregraduated every 10 mm and figured every 100 mm. Meter. They areconvenient for measuring shorts lengths.

ACCESSORIES(Instruments for Marking Stations)

Arrows (Chain Pins):They are also called as marking or chaining pins and are used to mark theend of chain during the process of chaining. They are made up of goodquality hardened and strengthened steel wire of 4mm in diameter. Thearrows are made 400 mm in length. They are pointed at one end ofinserting in to the ground. The other end is in to a ring.

Wooden Pegs:These are used to mark the positions. They are made of hard timber andtapered at one end. They are usually, 2.5 cm square and 15 cm long. Butin soft ground 40 to 60 cm long and 4 to 5 cm square is suitable. Theyshould be driven in the ground with about 4 cm lengths, projecting abovethe ground.

CHAIN

ARROWS (CHAIN PINS)

WOODEN PEG

RANGING RODS/POLES

Ranging rods:Used for making the positions of stations and for ranging. They are madeof seasoned timber of teak, blue pine, or deodar. They are circular oroctagonal in cross section of 3 cm diameter. Lower shoe is 15 cm long.They are made in two sizes as 2 meters and 3 meters and are divided into equal parts each 0.2 m long. They are painted alternatively black andwhite or red and white. Now a day instead of timber, mild steel hallowpipes are used.

Ranging Poles:Similar to the ranging rods but are heavier, they vary in length from 4 mto 6 m or more. Used in the case of very long lines.

Offset Rod:Similar to the ranging rod, they are usually 3 m long and is divided intoparts each 0.2 m length. Top is provided with an open ring for puling orpushing the chain through a hedge. It has two short narrow vertical slots.It is used for aligning short offsets.

Contd

Laths:Useful for ranging long lines, also used over uneven ground where theranging rod is not visible due to obstructions, they are light, cheap, beingwhite; they are easily visible at a great distance. Unusually 1.0m long

Whites:When the ranging rod is not available or insufficient, whites are used.These are thin strip of bamboo and 40 cm to 1 m in length. One end issharp and the other end is split for inserting pieces of white papers. Theyare also useful for temporary marking of counter points.

Plumb Bob:The plumb bob is required when measuring the distance along slopes inorder to transfer points to the ground. It is also used for testing theverticality of ranging poles.

Contd

ABNEY LEVELContd

In measuring the length of a survey line called chain line, it isnecessary that the chain should be laid out on the ground in astraight line between the end stations.

RANGING:The process of establishing intermediate point on a straight line betweentwo end points is known as rangingRanging must be done before a survey line is chained. It may be necessary toestablish intermediate points prior to chaining when chain line is muchlonger. Ranging may be done by direct observation by the naked eye or byline ranger or by Theodolite. Generally, ranging is done by naked eye with thehelp of three ranging rods.

RANGING OUT SURVEY LINE

RANGING

DIRECTRANGING

INDIRECT /RECIPROCALRANGING

Direct Ranging: When intermediate ranging rods are fixed on a straight line by directobservation from end stations, the process is known as direct ranging. Directranging is possible when the end stations are intervisible. Assume that A and B two end stations of chain line, where two ranging rods arealready fixed. Suppose it is required to fix a ranging rod at the intermediate point P on thechain line in such a way that the points A, P & B are in same straight line. The surveyor stands about two meters behind the ranging rod at A by lookingtowards line AB. The assistant holds ranging rod at P vertically at arms length the rod should beheld tightly by the thumb and forefinger. Now the surveyor direct the assistant to move the ranging rod to the left orright, following a proper code of signals until the three ranging rods comeexactly the same straight line. The ranging will be perfect, when the three ranging rods coincide and appear asa single rod. When the surveyor is satisfied that the ranging is prefect, he signals theassistant to fix the ranging rod on the ground. By following the same procedure, the other ranging rods may be fixed on theline.

Contd

Here an intermediate point Pis set to rang a chain line.

Here a point P is set fartherfrom point B to rang a chainline .

Indirect or Reciprocal Ranging: Indirect ranging is used when the end stations are not intervisible due to high

ground or a hill or if the ends are too long. In such cases, intermediate pointscan be fixed on the survey line by a process known as reciprocal ranging.

Let A & B be the two stations with rising ground or a hill. Let two chainmen with ranging rods take up positions at M and P, such that,

chainmen at M1 can see both rods at P1 and B and the chainmen at P1 can seethe ranging rods at M1 and A.

The chainmen at P1 directs the chainmen at M1 to shift the ranging rod at M2in line with A and then chainman at M2 directs the chainmen at P1 to shift theranging rod to P2 in line with B, by successively directing each other to be in linewith the end points.

Their positions will be changed until finally they are both in line with A & Bexactly on line AB.

Now the four ranging rods at A M P & B are on same straight line. This method may also be used in ranging a line across a valley or river.

Contd

Elevation

View From Top

SIGNAL GIVEN BY THE SURVEYOR MEANING OF THE SIGNALRapid sweep with right hand.(Fig.(a)) Move considerably in that direction (to

your left).Slow sweep with right hand. Move slowly to your left .Right arm extended. (Fig.(b)) Continue to move to your left.

Right arm up and moved to the right. Plumb the rod to your left.Rapid sweep with left hand. (Fig.(c)) Move considerably in that direction (to

your right).Slow sweep with left hand. Move slowly to your right.Left arm extended. (Fig.(d)) Continue to move your right.

Left arm up and moved to the left. Plumb the rod to your right.Both hands above head and then brought

down. (Fig.(e))Ranging is correct.

Both arms extended forward horizontallyand brought down quickly.

Fix the ranging rod.

CODE OF SIGNALS

Pictorial Representation

(a) (c)(b) (e)(d)

ANY QUERIES

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