Instruments for chain surveying 1. Chain 2. Tape 3. Arrows 4. Rang Rangin ing g rod rods s 5. Cros ross st staff aff
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Plumb bo bob !amme !ammer" r"#o #ood oden en malle mallett %ffs %ffset et rods ods Pegs
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10. Chains 11. 't is used to measure the distan(e between two points on the ground. The (hain is (omposed of 1)) *or+ 15) pie(es of gal,ani-ed mild steel wire 4mm in diameter (alled lins. The ends of ea(h lin are bent into a loop and (onne(ted together b/ means of three rings. The ends of the (hain are pro,ided with brass handles for dragging the (hain on the ground. 0etalli( tags are fied at ,arious distin(ti,e points of the (hain to fa(ilitate ui( reading. The length of the (hain is measured from the outside of one handle to the outside of the other. 0etri( (hains 12. 0etri( (hains are either 2)m *or+ 3)m in length. %ne metre is di,ided into 5 lins ea(h of ).2m. The least (ount of metri( (hain is ).2m. The length of the lin is the distan(e between the (enters of the two (onse(uti,e middle rings. To enable the reading of fra(tions of a (hain without mu(h diffi(ult/ tallies are fied at e,er/ fi,e meter length for (hains of 2)m and 3)m lengths. *ee.fig.+ mall brass rings are pro,ided at e,er/ meter length e(ept where tallies are atta(hed. 'n metri( (hains readings are started from ends in(reasing towards the (entre. The tallies in the (hain are as shown in fig below. ngineer7s (hain 13. The ngineer7s (hain is 1))ft. long and (onsists of 1))lins ea(h lin being 1ft long. 't is used in all engineering sur,e/s. 8unter7s (hain 14. The 8unter7s (hain is 66ft. long and is di,ided into 1)) lins ea(h ).66ft long. 't is ,er/ (on,enient for measuring distan(es in miles and furlongs. Re,enue (hain 1
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Re,enue (hain is 33 ft long and (onsists of 16 lins ea(h of 2
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ft long. This (hain is mainl/ used for (adastral sur,e/.
16. 17. Tape 1$.Tapes are used to measure the lengths to de(imal pla(es a((ura(/. 't is also used to measure the offset distan(e from main sur,e/ line. Tapes are made of ,arious materials and are therefore di,ided into 4 (lasses
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Cloth *or+ 9inen tape 0etalli( tape teel tape 'n,ar tape 19.Cloth (or) Linen tape 2). There are (losel/ wo,en linen *or+ s/ntheti( material and are ,arnished to resist the moisture. A metal ring is atta(hed to the outer end of the tape it in(ludes the length of the tape. These are a,ailable in 1)m 2)m : 3)m. a(h metre length is di,ided into 1) parts ea(h part is also di,ided into 1) di,isions. a(h di,ision ha,e a length of 1(m or ).)1m therefore least (ount of the tape is ).)1m. 't is easil/ affe(ted b/ damp. 't7s length gets altered b/ stret(hing and is liel/ to twist and tangle during measurement due to used therefore not used in pre(ise measurements. 21.Metallic tape 22. 't is linen tape with brass *or+ (opper wires wo,en into it longitudinall/ to redu(e stret(hing. As it is ,arnished the wires are not ,isible. These are a,ailable in 2m 5m 1)m 15m 2) and 3)m lengths. The measurements are mared as lie in linen tape. 't is (ommonl/ used for measuring offsets. 23.Steel tape 24. These are a,ailable as lie all length in metalli( tape and are 6 to 16mm wide. The marings in this tape are little different from metalli( tape. ,er/ meter is di,ided into 1) parts ea(h is (alled 1 de(imeter. a(h de(imeter is eual to 1)(m. ;or first 1)(m measurements are further di,ided into 1)parts. 25.Invar tape 26. This is made of an allo/ of ni(el 36< and steel 64< ha,ing ,er/ low (oeffi(ient of thermal epansion. 't is 6mm wide and a,ailable in lengths of 3)m 5)m : 1))m. 't is soft so it (an be handled (arefull/. 't (annot be used for ordinar/ wor. 2. Arrows 2$. 't is used to mar the points on the ground or to mar the end of ea(h (hain during the (haining pro(ess. 't is made of hardened and tempered. steel wire 4mm in diameter and length of 4))mm. These are pointed at one end whereas a (ir(ular ring is formed at its other end as shown in fig. 't is important to mar the (hain lengths in (haining operation. 'n general ten arrows are gi,en to one (hain.
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30. Ranging Rod 31. These are made of well seasoned straight grain timber *or+ steel tubular rods. These are used for maring a point in su(h a wa/ that the position of point (an be (learl/ and ea(tl/ seen from some distan(e awa/. These are 3(m to 5(m in diameter and 2 or 3m long. To fi the ranging rod on ground its bottom end is pointed b/ pro,iding (ross=shoe. These are painted with alternate bands of either red and white or white and bla( of 2))mm length. ometimes these are used to mar the permanent points. 'n order to mae them ,isible at a distan(e the/ are painted alternati,el/ bla( and white *or+ red and white su((essi,el/. #hen the/ are at a (onsiderable distan(e red and white *or+ while and /ellow flags about 25(m suare should be fastened at the top. 32. Cross staff 33. This instrument is used for finding the foot of the perpendi(ular from a gi,en point to a line and setting out a right angle at a gi,en point on a line. To set out a right angles the following two t/pe of (ross staffs are used. i. %pen (ross staff ii. ;ren(h (ross staff 34.Open cross staff 35. The simplest form of (ross staff is the open (ross staff shown in fig. 'n (onsist of two pairs of ,erti(al slits pro,iding two lines of sight mutuall/ at right angles. a(h pair (onsists of 2 ,anes one is e/e ,ane and there one is ob>e(ts ,ane. 36.rench cross staff 3. 't (onsists of an o(tagonal brass tube with slits on all eight sides. 't has an alternate ,erti(al right slit and an opposite ,erti(al window with a ,erti(al horse hair or a fine wire on ea(h of the four sides. These are used for setting out right angles. %n the other sides are ,erti(al sits whi(h are at 45) to those pre,iousl/ mentioned for setting out angles of 45).
3$. 3&.The base (arries a so(et so that is ma/ be fitted on the pointed staff when the instrument is to be used. 0. !"um# #o# 41. 't is used while measuring distan(es on sloping ground and transfer to the le,eled ground. 't is made of steel in a (oni(al shape with a thread (onne(ted at the (entre. 't is generall/ used for (entering.
2. $ammer 43. 't is used to gi,e blows to fi the peg on the ground. . %ffset rod 45. 't is similar to the ranging rod but is usuall/ 3m long. The top is pro,ided with a stout open ring re(essed hoo for putting or pulling the (hain through a hedge or other obstru(tion.
46. 7. !egs 4$. There are used to mar definite points on the ground. These are made of hard timber and are tapered at one end. The/ are usuall/ 15(m length with 3 to 5(m diameter (ir(ular in shape *or+ 3 to 5(m suare in shape. The pointed end of peg is (o,ered b/ iron shine for eas/ dri,ing into the ground. 4&. Ranging 5). The operation of establishing intermediate points on a straight line between the terminal points is nown as ranging. 'f the line is short or the end station is (learl/ ,isible it is eas/ to put the (hain in true alignment. ?ut if it is long or the end station is not (learl/ ,isible it is ne(essar/ to pla(e intermediate ranging rods to maintain the dire(tion. 't ma/ be done b/ e/e *or+ instrumentall/ b/ using a line ranger or a Theodolite. 51.T/pes of ranging@ Ranging is of two inds@ i+ ire(t ranging ii+ 'n= dire(t ranging &2.'irect Ranging( 53. This is done when the two ends of the sur,e/ lines are inter=,isible is uite (ommon in flat (ountr/. 'n su(h (ases ranging (an either be done b/ e/e or through some opti(al instrument su(h as a line ranger or a Theodolite.
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54. ;i the ranging rods at the two gi,en stations where pegs are alread/ dri,en on the ground. The follower stands behind station A and dire(ts the leader with ranging rod to (ome in line with A? b/ signals of ranging #hen the ranging rod (omes in the line of A? the follower dire(ts the leader to fi the ranging rod in position. 9et the intermediate point be C whi(h should be less than 2)m " 3) m. Bow the leader taen another ranging rod and stands between A : ? about 2"3 distan(e from A. The follower dire(ts the leader to (ome in line of A? b/ using signals of ranging. As and when the point is lo(ated in the line of A? the follower instru(ts to fi the ranging rod in position. 9et the other intermediate position be whi(h is less than 2) m " 3) m from ? Bow A ? C and are in one line. 55.Bow the leader and follower measure the distan(e b/ measuring along A C and ?. 56. Indirect Ranging : 5. 'ndire(t *or+ re(ipro(al ranging is resorted to when both the ends of the sur,e/ line are not inter=,isible either due to high inter,ening ground or due to long distan(e between them. 5$.The end points are not inter=,isible due to 1+ Rising ground between the ends 2+ !ill between the ends 3+ 9ong distan(e between the ends
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5&. ;i the two ranging rods at the gi,en stations A and ? whi(h are not inter=,isible due to rise in the ground le,el. ele(t two intermediate points 0 1 and B1 su(h that from ea(h point both A and ? are ,isible. The person at 0 1 dire(ts the person at B 1 to mo,e to a new position B 2 in line with 01?. The person at B 2 then dire(ts the person at 0 1 to mo,e to a new position 0 2 in line with B2 A. The person at 0 2 dire(ts the person at B 2 to a new position B 3 in line with 0 2?. The person at B 3 dire(ts the person at 0 2 to a new position 0 3 in line with B 3 A. The pro(ess is repeated till the points 0 and B are lo(ated in su(h a wa/ that 0 finds the person at B in line with A? and the person at B finds the person at 0 in line with A?. After fiing the points 0 and B other points are also fied b/ dire(t ranging and the length of the line is measured. 60.
61.Use of Distomat/Electronic Distance Meter (EDM) 62. Bowada/s for measuring distan(es ele(troni( euipments (alled ele(tromagneti( distan(e measurement *0+ instruments ha,e (ome in the maret. The/ rel/ on the measurement of ele(tromagneti( wa,es and measuring e,en fra(tion of wa,elength b/ phase differen(e te(hniue. The/ e,en displa/ the distan(e measured. The/ are (ostl/ and deli(ate. !en(e for ordinar/ sur,e/ing the/ are not used (ommonl/.
63. 64.CHA! "U#$E%!& 65.Chain sur,e/ is suitable in the following (ases@ 66. *i+ Area to be sur,e/ed is (omparati,el/ small 6. *ii+ 8round is fairl/ le,el 6$. *iii+ Area is open and 6&. *i,+ etails to be filled up are simple and less. ). Prin(iple of (hain sur,e/ is triangulation. 'n (hain sur,e/ing onl/ linear measurements are made. in(e triangle is the onl/ figure that (an be plotted with measurement of sides onl/ in (hain sur,e/ing the area to be sur,e/ed should be (o,ered with a networ of triangles. ;igure shows a t/pi(al s(heme of (o,ering an area with a networ of triangles. Bo angle of the networ triangles should be less than 3) to pre(isel/ get plotted position of a station with respe(t to alread/ plotted positions of other station. As far as possible angles should be (lose to 6). !owe,er the arrangements of triangles to be adopted depends on the shape topograph/ natural and artifi(ial obsta(les in the field.
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Betwors of triangles
3. "tation: tation is a point of importan(e at the beginning or at the end of a sur,e/ line. Main station: These are the stations at the beginning or at the end of lines forming main seleton. The/ are denoted as A ? C et(. 4. "'siiar* or tie stations: These are the stations sele(ted on main lines to run auiliar/"se(ondar/ lines for the purpose of lo(ating interior details. These stations are denoted as a b ( .... et(. or as 1 2 3 ... et(. 5. +ase line: 't is the most important line and is the longest. Dsuall/ it is the line plotted first and then frame wor of triangles is built on it. 6. Detail lines: 'f the important ob>e(ts are far awa/ from the main lines the offsets are too long resulting into ina((ura(ies and taing more time for the measurements. 'n su(h (ases the se(ondar/ lines are run b/ sele(ting se(ondar/ stations on main lines. u(h lines are (alled detail lines. . $. C,ec- lines: These are the lines (onne(ting main station and a substation on opposite side or the lines (onne(ting to substations on the
sides of main lines. The purpose of measuring su(h lines is to (he( the a((ura(/ with whi(h main stations are lo(ated. &. 0."election of "tations $1.The following points should be (onsidered in sele(ting station points@ $2.
*i+'t should be ,isible from at least two or more stations.
$3.
*ii+ As far as possible main lines should run on le,el ground.
$4.
*iii+ All triangles should be well (onditioned *Bo angle less than 3)+.
$5.
*i,+ 0ain networ should ha,e as few lines as possible.
$6.
*,+ a(h main triangle should ha,e at least one (he( line.
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*,i+ %bsta(les to ranging and (haining should be a,oided.
$$. *,ii+ ides of the larger triangles should pass as (lose to boundar/ lines as possible. $&. 90.
*,iii+ ;reuent (rossing of the roads should be a,oided.
