surveying for engineers

8/20/2019 Surveying for Engineers

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2/34

C o t e n t s

I n t r o d u c t i o n

B a s i c p r i n c i p l e s

P l a n e T a b l e S u r v e y i n g

C h a i n S u r v e y i n g

l e v e l l i n g

T a b l e s

p a g e

1

8

1 1

9


3/34

P I N

EQUIPMENT

B O A T L E V E L

A L l D A D E

o

T R I P O D

P L U M O

F i g 1


4/34

PL NE T LE SURVEY

R A D I A T I O N M E T H O D

F a c t o r y

------

,,\

M A R T I N S L A N E

A P L A N O F A T Y P I C A L S I T E

F i g 2

I


5/34

CH IN SURVEYING

Chai n Sur veyi ng has l ong been es t ab l i s hed as t he eas i es t

an bas i c f or m of l and mea$u rement and i s s t i l l i n common us e.

3as ed on t r i angul at i on and cons i s t i ng of car r y i ng out t he

s ur vey i n t he f i el d and pl ot t i ng t he s ur vey t o s cal e i n t he

dr awi ng of f i ce f r om r ecor ded meas ur ement s i n t he f i el d book.

~t i s a j ob f or t wo peopl e t he s ur veyor and hi s as s i s t ant .

Ther e ar e s ever al pos s i bl e i naccur ac i es whi ch may occur

' . ' henar r y i ng out a chai n su r vey and gr eat car e s houl d be

~aken t o avoi d t he, . The mos t common bei ng conf us i ng t he

- ~l l i es , m scount i ng t he l i nks , t he chai n havi ng knot s i n

i nk j oi nt s , bent l i nks , t he chai n not bei ng l ai d out i n a

s t r ai ght l i ne bet ween s t at i ons , i ncor r ec t book i ngs , m s cal l ed

· i ens i ons and booki ng of f s et s at wr ong poi nt s . Pr ac t i c e i n

~he f i el d wi l l hi ghl i ght s ome of t hes e pr obl ems as t her e i s

~o subs t i t ut e f or expe r i ence i n t he us e of a chai n.

E Q U I P M E N T

The bas i c equi pment f or chai n s ur veyi ng i s t he me t r i c

chai n 20met r e s i n l engt h wi t h 100 l i nks each . 20met r es i n

_ e. t h. Ever y t ent h l i nk i s mar ked by a br as s t ag or t el l er

' - it : - t nt er medi at e t ags f or ever y l i nk . The chai n i s made of

E eel wi r e and gr eat car e s houl d be t aken when f ol di ng s o as

~o avoi d ent angl ement and bendi ng t he l i nks . When t he chai n

i s t o be us ed and l ai d out i t i s done by gr as pi ng bot h

: a~dl es of t he chai n and t h r owi ng i t out i n one oper at i on and

~ . en s t r ai ght ened out ens ur i ng al l l i nks and j oi nt s ar e

out s

t

r etched pr oper l y .

Ther e ar e t wo ot her chai ns us ed t hes e bei ng t he Gunt e r

Chai n whi ch i s 66 f eet i n t ot al l engt h wi t h 100 l i nk s of

7. 92 i nches , and t he Engi neer s Chai n 100 f eet i n l engt h and

: ~E_ 00 l i nks each a f oot l ong and mar ked at 10 f oot

i : r : t er val sv: it h t al l i es acc or d. ingLy ,

T a p e s

Thes e ar e made of s t eel bei ng t he mos t accur at e and bei ng

r- e I ' e-r-e d t o l i n en t apes . They ar e c ornmon.l y i n l engt hs of 10,

20 and 30 met r es and ar e us ed t o meas ur e of f s et s t o t he mai n

c hc i . n l i ne.

1 1


6/34

EQUIPMENT

9 0

T H E M E T R I C C H A I N

T A P E

C H A I N A R R O W S

g

3

R A N G I N G P O L E S

P O L E S U P P O R T /

. . e

1 2


7/34

A r m l W S

.-•. 0 ':c ar e used t o mar k t he end of each chai n l i ne and ar e

J OOmm t o 450rmTli n l engt h and car

r-y

a r ed cl ot h

so t hat t hey can be easi l y spot t ed on t he gr ound.

p o l e s

: ~ese er e usual l y 2 met res i n l engt h of wood or met al

. : n bands al t er nat el y i n r ed, whi t e and bl ack.

b o o k

: : : e_d oak appr oxi mat el y 100mm x 200mmwi t h ent r i es

at t he back cont i nui ng t o t he f ront so t hat t he

_ ._:~~c ar e r ecorded i n t he same di r ect i on as t he Sur veyor

c. : : ':':::F' al ong t he chai n.

C~~~:: ~. r eent er ed i n t he book such as hedge ' , f ence8,

~~~ coundar i es, bui l di ngs, t r ees, manhol es and pol es

et c.

e af or e ment i oned ar e i l l ust r at ed i n Fi g. J .

or ocedur e i E t o make a r econnai sance of t he si t e

t he f , ener~ shape and l ayout and any ot her

o be sur veyed. Then deci de on t he f r amewor k of

- . : : . - - -- a i on and dr i ve i n st at i on pegs A. B. C. as shown i n

. . : ~€ st at i ons t o be f i xed by t aki ng t wo t i c l i nes t o

: ~o t hat i t can be r e- l ocat ed i f a r et urn vi si t i s

C ~:.~

S>

I f t he di st ance between t he st at i ons exceed a

: : ' e: : : - t hi ne i n wi t h an i nt ermedi at e r angi ng pol e as

· f . 5. Then by p~oceedi ng up t he chai n l i ne f r om

. easur e wi t h 90 of f set s, f eat ur es as bef or e

u~t i l you have r eached t he end of t he l i ne A- B,

• ::. - ;;0 n al l t he r el evant i nf ormat i on. Thi s i s t hen

- E

~or B- C and C- A. I f t he 90

0

o f f set s exceed

9

metres

- ~~. t en an Opt i cal squar e can be used t o gi ve gr eat er

r . = - - : _ ~ : or t he J : 4: 5 Tr i angl e r ul e empl oyed usi ng a t ape.

r act i cal nature of t he sur vey has been car r i ed

- ~r _e: : ul l v checki ng t hat al l t he i nf ormat i on r equi r ed has

. ' : not ed and l oeged t he Eur vey can be dr awn t o scal e

: f:..'.'.in[;

of f i ce.

3


8/34

R E C O N N A I S S A N C E

S E T T I N G O U T S T A T I O N S

T h e S · e

_.CllJAP . ~~. _

F i g

4


9/34

CH IN SURVEYING

i n t e r m e d i a t e r a n g i n g

p o l e

S E T T I N G U P C H A I N L I N E

F i g 5

1 5


10/34

C L I N O M E T E R

_ ~s ~ s t r ument i s us ed f or meas ur i ng s l opes of 3 or

i s s i mpl y i l l us t r at ed bel ow. By f i r s t l y vi ewi ng

~ns t r u ment on t he hor i z ont al pl ane t he i ns t r ument

and f o c us s ed ont o t he r angi ng pol e up t he

ope wi t h t he count er wei ght i n t he ver t i cal po s i t i o n

- ~ ~_ evat i on can be r ead on t he di al , i n t hi s cas e 30

0

•

- s t r ument i s hand hel d and i s mos t us ef ul f or

s l opes qui c k l y and eas i l y gi v i ng i ns t ant r eadi ngs

6


11/34

CH IN SURVEY

S L O P I N G S I T E S

To meas ur e Leg s l opes gr eat er t han

o

3 ,

meas ur e conveni ent hor i z ont al

di s t ances , pl umb down t o gr ound l evel

t o f i x poi nt f r om whi ch t o t ake next

meas ur ement .

B

~e of s l ope wi t h CL I l W · : : ETER

0 11

Tr i gonomet r y AB=AC

Cose{

meas ur e s l ope

>--

. . . . - - - -

-

R A N G I N G O V E R H I L L S

----

-

CLES

c

-

f t

and

B

As s i Et ant ~i t h pol e 2t D l i nes i n s ur veyor

t C on l i ne AD. Sur veyor l i nef ' i n pol e at D on l i ne

s equence ~i t h f our pol es i n l i ne.


12/34

b d

e

B

E

cai n l i ne t hr ough

A. B. C.

set out equal of f set s t o a. b. c.

i ~ d. e. Set of f set s of l engt h as bef or e t o f i x D E.

~~ cont i nuat i on of mai n l i ne t hrough

F . G.

et c.

~ ~ ~ ~ ~D

1Il:dll \IIWl G A C R O S S A R I V E R

-----

__ ~_------=rtIVER -

: es at

A

B

on chai n l i ne.

AD

at Rt . 1s t o

AB.

Pol e

C

- : na

t

AC=CD. DE

at Rt . 1s t o

AD, wi

th

E. C. B.

on st r ai ght

: : en

AB =DE.

E Y O F L A K E O R W O O D

- - ~ f r aJ ework of chai n l i nes

_ =

ar ea and t r i angul at e

- _ - i es acr oss t he cor ner s

_:'e';

C:- IN TRAVERSING .

8


13/34

I T R O D U C T IO N

Thi s book has been set out t o i l l ust r at e t he f undament al

basi s of l and measur ement and pr ocedur es t o adopt when

sur veyi ng ar eas of l and. The act ual pr act i ce of car r yi ng

out surveys has not changed much over t he year s wi t h onl y

per haps t he r ef i nement and advanced equi pment now i n use.

Wost of t he procedures det ai l ed i n t hi s publ i cat i on ar e i n

cor r~onpr act i ce and wi l l gi ve a good gr oundi ng t o

Ar chi t ect ur al , Sur veyi ng and Bui l di ng st udent s.

I t i s emphasi sed t . at onl y pract i ce i n t he f i el d wi l l

gi ve a good and t hor ough under st andi nG of t he met hods

out l i ned her e and t he key bei ng accur acy i n per f ormance.


14/34

L V L L IN

_ _ _ ~as i c i ns t r ument f or l evel l i ng i s t he sur veyor s

.••:;,_


15/34

~~c~~ f r o. one t r ans par ent mat er i al t o anot her

- - ~~ec~i on. F or exampl e, a s t i c k par t l y i mmer s ed i n

- _ e ar s t o be s har pl y bent at t he s ur f ace of t he wat er

r-or above t he wat er s ur f ace. Thus , i n pas s i ng

: e~s t he r ays of l i ght wi l l be bent or r ef r ac t ed as

e - . ' ; ; ih a convex l ens t he r ays of l i ght wi l l

~ _ as s i ng t t r o ugh i t .

c o _ _ea e l ens t he r ays wi l l di ver ge on pas s i ng t hr ough

l ens i s s ui t abl e as a bur ni ng gl as s whi l e

t hr ough a convex l ens wi l l c onver ge on a

he pr i nc i pal axi s cal l ed t he pr i nc i pal f ocus

- : : '~: : : . The di s t ance f r om t hi s poi nt t o t he opt i cal

-::e

: ens i s t e r med t he f ocal l engt h of t he l ens .

F i g 2

ib.IS,

~ c ~ ex l ens ~i l l pr oduce an i mage on a s c r een

T_ i s i mat ; e i s t er med a Real I mage .

ens however causes t he l i ght r ays t o di ver ge

pr-oduced backwar ds t o t he pr i nc i pal f ocus .

i . c . gev: i l l be s een on a s c r een at F and t hi s i s

' , - i r t ualI mage .

l en t h of a convex l ens i s pos i t i ve (+)

l engt h of a concave l ens i s negat i ve ( - )

i on of di f f e r ent s haped l enses wi l l pr oduce a

~ocal l engt h r el at ed t o t hei r i ndi v i dual f ocal

- _ , e expr e s s i on

I

•••••••••••

: - C~_ l engt h of t he combi ncat i o n, or , c ompound l ens ,

- ~ ov: n as t he jiowe r of t he l ens .

I

et c .

fJ'

t he f ocal l engt h of i ndi v i dual

l ens es .


16/34

P r o d u c t i o n o f a n i m a g e

An obj ec t bei ng vi ewed t hr ough a l ens i s c ons i der ed t o

cons i s t of a number of connec t ed poi nt s , each r adi at i ng t V10

r ays of l i ght ; one r ay pas s i ng t hr ough t he opt i cal cent r e of

t he l ens wi t hout bei ng r ef r ac t ed, t he ot her , par al l el t o t he

pr i nc i pal axi s , r ef r ac t ed t hr ough t he f ocal poi nt , bot h

i nt er s ec t i ng t o pr oduce an i nver t ed r eal i mage ( See F i g. 3. )

v

/t / A / T

{)I../ ••

mta JlCT~~

~a~~

~K

&JUc,

VltW£D

f

F i g 3

~~D /M/lt;E CF

Po/AlT WED

(R lA L

/MIlGE)

f ocal l engt h f

U f or a l ens .

Ther e i s a def i ni t e r el at i ons hi p bet ween t he

and t he obj ec t di s t ance

V

t o t he i mage di s t ance

Thi s i s expr es s ed as :

I I I

f

=

1 1

and

I

1

I

f

=

V

U

f or a convex l ens .

f or a concave l ens ( wher e f i s

negat i ve)

As t he i mage mus t be pr oduced on t he s ame pl ane as t he c r OLS

hai r s of t he t el es c ope of s ur veyi ng i ns t r ument s , and t he

di s t ance f r om obj ec t t o l ens wi l l var y caus i ng a pr opo r t i onal

var i at i on i n val ue U, i t i s es s ent i al t o p rov i de adj us t ment of

t he l ens by a f ocus s i ng mechani s m

A s i ngl e l ens hov: ever pos s es s es a number of f aul t s , t he t wo

i por t ant ones bei ng:

( a) Chr omat i c aber r at i on; v hit e l i ght i s s pl i t i nt o i t s

co ponent c ol our s on r ef r ac t i on, t er r - : ed di s per s i on ,

and due t o di f f er i ng angl es of r ef r ac t i on f or each

col our t he i mage t ends t o be bl ur r ed and s ur r ounded by

a hal o of c ol our s .

Thi s i s us ual l y over come by us i ng t wo l ens es of

di f f er ent mat er i al , e. g. one of c r own gl as s and one of

f l i nt gl as s .

( b) Snher i cal ber r at i onj Thi c i s caus ed by var i ous r ays of

l i Ght f I l i ng on t he l ens not bei ne; r-e f r-ac ted t o pa s s

exac tLy thr - ough t he SC: . T: i eocal poi nt . ~' l ) i f'auI t i s

cont r ol l ed by us i ng t hi n

Leris

es and r es t r i c t i ne; t he

obj ec t t o be vi ewed t o an ar ea c l os e t o t he pr i nc i p~l

axi s of a f l c : . . tur vat ur e l ens .

2 1


17/34

T h e t e l e s c o p e

The sur veyor s t el escope show~ i n Fi g. 4. provi des a l i ne of

col l i mat i on passi ng t hr ough t he opt i cal cent r es of t he l enses

and t he cross hai r s. The e epi ece magni f i es bot h t he r eal

i mage and t he cross hai r s i n t he same pr oport i on as t hese ar e

bot h on a common pl ane. The eyepi ece i s usual l y t he Ramsden

t ype, consi st i ng of t wo pI ano- convex l e~ses mount ed a shor t

di st ance apar t i n a sel f - cont ai ned case, which i s t hr eaded on

t he out si de t o al l ow i t t o be screwed f ' owar-d or back i n t he

t el escope body t o br i ng t he cr oss hai r s and i mage i nt o cl ear

f ocus. Thi s ar r angement of l enses r educes spher i cal aberr at i on.

The obj ect gl ass i s usual l y a compound l ens t o r educe

chromat i c aber r at i on.

F o c u s s i n g

)

/MIlCr~

Fo.(?N/£D

BY

#£'

PIECt.

I' 12/AJ C /P 4L.. 4 ;,r C OLJ.IM I1 7Io A /

1..11./ o . t : SI(jIlr:

F i g 4

Two f orms of f ocussi ng mechani sm ar e used t o br i ng t he

i mage ont o t he cr oss- hai r pl ane as t he di st ance of t he obj ect

f r om t he t el escope var i es. These ar e:

( a) Ext er nal f ocussi ng: The body of t he t el escope i s made

of t wo concent r i c cl ose f i t t i nG bar r el s, t he obj ect

gl ass mount ed i n one and t he eyepi ece and cr oss- hai r s

i n t he ot her . A r ack and pi ni on mechani sm oper at ed by

t he f ocussi ng scr ew advances or r et r act s one t ube i n

r el at i on t o t he ot her , t hus i ncreasi ng or r educi ng t he

di st ance bet ween obj ect gl ass and eyepi ece/ cross- hai r s.

Thi s met hod was common on ol der i nst r ument s and i s more

accur at e f or t acheomet r y pur poses, but has t he

di sadvant age t hat wear on t he t ubes may al l ow ent r y of

wat er , dust , et c. , and i mpai r t he ef f i ci ency of t he

i nst r ument .

Cb) I nt er nal f ocussi ng: A doubl e concave l ens mount ed on ( )

f r ame i s f i t t ed i nsi de a one pi ece t el escope body

bet ween t he obj ect and eyepi ece l enses. The f r ame

poci t i on i s adj ust abl e by means of a r ack and pi ni on,

as bef or e, whi ch sl i des t he l ens t ov: ar ds or away f r om

t he obj ect gl ass.

22


18/34

The concave l en di s pe r se s t he l i gh t r ays f r om t he

obj ec t gl as s t o gr eat er or l es s er degr ee dependi ng on

t he po s i t i on of t he l ens and t hus al l ows f ocus s i ng of

t he i mage on t he c r os s - ha i r s . The di s advant age of t hi s

met hod i s t he l os s of br i l l i ance due t o t he ext r a l ens .

C r o s s - h a i r s

Or i gi nal l y , s pi der s yeb was us ed, but t hes e br oke eas i l y

and wer e d i f f i c ul t t o r epl ace. Today, ver y f i ne l i nes ar e

et ched on a pi ece of ver y t hi n opt i cal gl as s f as t ened t o a

r et i cul e , f or m ng an i nt e r changeabl e caps ul e whi ch f i t s

i nt o a f l anged met al r i ng cal l ed t he di aphr agm , hel d i n t he

t el es cope bar r el by f our caps t an headed s c r ews - whi ch s houl d

onl y be t ouched when changi ng or maki ng maj or adj us t ment s t o

t he c r os s - ha i r s .

P a r a l l a x

Thi s t er m r ef er s t o r el at i ve mot i on bet ween t he obj ec t and

t he c r os s - hai r s when t he eye i s moved t o and f r o ac r os s t he

eyepi ece, and means t hat t he i mage and c r o s s - hai r s ar e not on

t he s ame pl ane. To el i m nat e par al l ax a pi ece of whi t e paper

i s hel d i n f r ont of t he obj ec t l ens and t heeye- pi ece moved i n

or out unt i l t he c r os s - hai r s s t and out c l ear and bl ack . The

t el es cope i s t hen f ocussed on t he obj ec t and t es t ed f or

par al l ax agai n, t he pr ocedur e bei ng r epeat ed i f neces s ar y

unt i l t he par al l ax i s el i m nat ed.

T h e s p i r i t l e v e l

Cor mnonl y f as tened t o t he

ba.r-r-e

I of t he t e l es cope on a

l evel l i r i g i ns t r ument , but us ua l l y on t he t op pl at e of a

Theodol i t e. The mor e s ens i t i ve s pi r i t - l evel s ar e bar r el

s haped cur ved gl as s t ubes , wi t h t he l es s s ens i t i ve onl y a

po r t i on of t he s ur f ace i s cur ved, when t hee' t er med non-

r ever s i bl e l evel s . The gl as s t ube i s f i l l ed wi t h et her or

al cohol wi t h a sm2. 11 ai r s pace l ef t t o f or m a bubbl e. These

f l ui ds ar e l es s vi s cous t han wat er , ~nd have a much l ower

f r e e z i ng poi nt , bu t a gr eat er ey- pans i on, s o t ha t a l evel l ef t

i n ver y hot s un may bu r s t .

The t op s ur f ace of t he t ube has gr aduat i ons et ched on i t

whi ch ai d i n cent r al i s i ng t he bubbl e i n t he cent r e of i t s r un.

The s ens i t i venes s of t he bubbl e i s def i ned as t he amount t he

ho r i z ont al axi s of t he t ube has t o be t i l t ed t o caus e t he bubbl e

t o move f r om one gr aduat i on mar k t o t he next ,

e g

1 di v i s i on

) 0 s ec . means a t i l t of ) 0 s ec . of ar c above t he ho r i z ont al

v.Ll L caus e a r un of one gr aduat i on.

23


19/34

The spi r i t l evel t u e i s e~c osed i n a met al case,

at t ached t o t he

body

of ne

L_

trur . entby one or t wo capst an

headed scr ews whi ch al

Lov

t

he t ube t o be adj ust ed so t hat i t

l onei t udi nal axi s i s par al l e t o t he pr i nci pal axi s of t he

Tel escope.

By t hi s means one can adj ust t he i nst r ument so t hat t he

l i ne of col l i mat i on i s hor i zontal , i . e. at r i ght a~gl es t o t he

pl ane of gr avi t y act i ng at t he cent r e of t he i nst r ument : Do

not adj ust t he capst an scr ews unl ess maki ng a maj or

cor r ect i on.

The cent r al i s i ng of t he bubbl e may be observed i n di f f er ent

ways. On some i ns t rument s t he t ube i s vi ewed i n a r ni r r or

hi nged t o an angl e of about 45

0

•

I n ot her cases an i nt er nal

m rror may be used, or a r i ght angl e pr i sm t o gi ve t he

sur veyor an i mage of t he bubbl e i n t he eyepi ece so t hat he

does no~ have t o move r ound t he i nst r ument .

Anot her met hod present s two hal f bubbl es i mages i n t he

f i el d of vi ew and t hese have t o coi nci de t o f orm one compl et e

bubbl e t o br i ng t he t el escope l evel .

The ci r cul ar or cat s eye bubbl e i s i nf er i or i n accur acy

t o t he l evel t ube but gi ves an appr oxi mat e l evel pl ane f or

i ni t i al C' ui ckset l evel l i ng pur poses.

T y p e s o f l e v e l s

DU. DV Level : The si mpl est f orm of l evel consi st s of a

bubbl e t ube at t ached t o a t el escope whi ch i s r i gi dl y f i xed

t o a hor i zont al l y r ot at i ng cent r e post and t op pl at e, i n i t s

t ur n connect ed t o a bot t om pl at e by t hr ee or f our l evel l i ng

f oot scr ews, whi ch can be adj ust ed t o br i ng t he spi r i t

l ev~ and t el escope axi s hor i zont al .

T~o condi t i ons ar e essent i al f or accur at e wor k.

1

The axi s

of t he

bubbl e t ube must be

par al l el

t o

t he

axi s of t he t el escope, i . e. l i ne of col l i mat i on.

2.

Bot h must be at r i ght angl es

t o ver t i cal

axi s of t he

i nst r u

ent .

Ti l t i ng Level or Qui ckset Level : An i mpr ovement on t he

Dumpy as t he t el escope can be pi vot ed i n t he ver t i cal

pl ane by means of t he t i l t i ng scr ew under t he eyepi ece end

of t he t el escope. I t i s onl y necessar y t o set t he

i nst r ument t o an appr oxi mat e hor i zont al pl ane by

re fer ence t o t he cat s eye bubbl e, t he t el escope bei ng

br ought l evel f or each si ght i ng by usi ng t he t i l t i ng scr e~.

)

e x a m p l e


20/34

Pr eci se Level : Thi s i s a devel opment of t he now al most

obsol et e Wye l evel and t he Ti l t i ng l evel .

The t el escope t ube may be t i l t ed and al so r evol ved i n i t s

mount i ngs so t hat b t aki ng t he mean of t wo r eadi ngs on

t he same st at i on a t r ue r eadi ng may be obt ai ned, t hi s

compensat i ng f or any error i n t he col l i mat i on of t he

i nst r ument .

e x a m p l e

T e r m s u s e d i n l e v e l l i n g

Bench r ar k: A f i xed poi nt on t he ear t h' s sur f ace whose

l evel above Or dnance dat um i s known.

Or dnance datun.e r~ean sea l evel t o whi ch al l ot her l evel s

and bench mar ks ar e r el at ed.

Back si ght : The f i r st si ght t aken f r om a gi ven l evel

posi t i on.

For esi ght : The l ast si ght t aken f r om a gi ven l evel posi t i on.

I nt ermedi at e si ght : Any ot her si ght t aken f r om t hi s l evel

posi t i on.

Hei Ght of I nst r ument : ( H. of I ) . The hei ght of t he l i ne of

col l i mat i on above t he dat um ( i . e.

si ht l i ne or pr i nci pal axi s of

t el escope. )

5


21/34

Reduced l evel : R. = Cal cul at ed hei ght or l evel of a

poi n a

0

e or bel ow t he dat um

Change Poi nt : The poi nt at wlri c h bot h a f or es i ght and

t hen a backs i ght ar e t aken ( i . e. when t he

l evel c hanges pos i t i on. )

M E T H O D

S e t t i n g u p t h e l e v e l

1. Open t r i pod l egs t o 60

0

and pr es s t he f eet f i r m y i nt o

gr ound.

2. Not e how i ns t r ument i s packed i n t he box bef or e

r emovi ng and l i f t out car ef u l l y , never by t he

t el es c ope t ube.

3. Sc r ew f i r m y ont o t r i pod head; never c r os s i ng t he

t hr eads .

4. Roughl y l evel t he i ns t r ument y adj us t i ng t he t r i pod

l egs , compl et e adj us t ment by means of t he f oot sc r ews ,

i . e. br i ng t he bubbl e t o t he cent r e of i t s r un.

p l a n

c : ;

~. axi s at r i c ; ht

of

ent :

Check t hat t her e i s no pl ay on t he axi s of t he

i ns t r ument . Tur n t el es cope over a p~i r of f oot s c r ews

o

and l evel - up. Then r ev r s e t ube t hr ough 180 • I f t he

bubbl e r uns of f cent r e br i ng i t hal f way back wi t h

f oot s c r eVl s and t he bal ance of t he way wi t h t he caps t an

he ded s c r ews on t he bubbl e t ube.

6


22/34

C o r r e c t i o n s

Cur vat ur e: as t he ear t.h i s cur ved, a hor i z ont al s i ght

does not gi ve t he t r ue r el at i e hei ght s of t wo poi nt s over

a l ong s i ght i ng di s t ance. See

Fig.6.

.

As

C

is

s o

smal l

c or . : par ed

o

2R i t i s i gno r ed and t he

expr es s i on

i s wr i t t en t hus

X2

2R

=

cor r e c t i on.

Di s t ance

2

d

2

i e

cur vat ur e

cor r ec t i on

meas ur ed

or

Di amet er of Ear t h 2R

Ref r ac t i on: di f f er i n~ at mos pher i c condi t i ons caus e t he

r ays of l i ght ent er i ng t he t el es cope t o be r ef r ac t ed, i e

bent , t owar ds t he ear t h' s s ur f ace t o gr eat er or l es s er

degr ee, s o t hat on a l ong s i gh t t he r eadi ng s een on t he

s t af f i s not on a t r ue hor i z ont al l i ne but be l ow i t and

near er t o t he ear t h' s s ur f ace t han i t i s bel i eved t o be.

Thi s er r or due t o r ef r ac t i on par t l y of f s et s t he er r or

due t o cur vat ur e. As an aver age f i gur e i t i s as s umed t ha t

t he er r or due t o r ef r ac t i on i s 1/ 7 t hat of cur vat ur e and i n

t he oppos i t e di r ec t i on.

The combi ned co r r ec t i on f or cur vat ur e

2

and r ef r ac t i on i s

us ual l y quot ed as a deduc t i on of 6 d

7 x 2R f r om t he s t af f

r eadl ng.

R

F i g 6

7


23/34

For s hor t s i ght s t : : &c i : : e r e: 1cei s s o smal l t 11Ci t t

De.

be

i gnor ed, but i n exac t I eve: l ~~ s i ght s s houl d not exceef i a

qua r t er of a m l e t o a O : : euncer t ai nt y caus ed by t hes e

er r or s . By t ak i ng back a. . f o r e- s i gh t s t o s t af f pos i t i ons at

near l y equal di s t ances f r o _ t : h e l evel t he s e f aul t s may be

cons i c i er ed cancel l ed and ar e no t cal cul at ed i n nor mal

l evel l i ng oper at i ons .

o

1

/)/S7,tftJCc~ ~

r

1~ y - - - - f - - . . 1 - J - - - . / {

Co

J

pound Level l i ng : i n whi . ch t he l evel s ar e obt ai ned onl y

by changi ng t he pos i t i on of t he i ns t r ument as one f ol l ows t he

undul at i ons of t he gr ound i n a l ong l i ne of l evel s , or t o

obt ai n c l ear s i ght s whi ch


24/34

L ND SURVEYING

G E N E R A L L Y

The mai n f unc t i on of car r y i ng out a pr ac t i cal l and

s ur vey i s t o as cer t ai n as accur at el y as pos s i bl e t he s i z e

and s hape of bui l di ng s i t es , f i el ds or ot her ar eas of l and

mas s es . They may have on t hem ponds , bui l di ngs or i nc l ude

ot her f eat ur es s uch as di t c hes , s t r eams and t r ees et c . whi ch

may need t o be r ecor ded and pl o t t ed on a s ur vey dr avr i ng.

Thi s i s gener al l y known as l and meas ur ement .

I n addi t i on t o t hi s i nf or mat i on i t wi l l al s o be

i mpor t ant t o· know how t he s i t e s l opes f or whi c h you wi l l

need t o car r y out a l evel s ur vey. Bas i c al l y i t i s f or m ng

a t hr ee di mens i onal pi c t ur e of a par t i cul ar ar ea of l and

wi t h poi nt s of el evat i on mar k ed on i t s o t hat ver t i cal

c an be t aken t h r ough s howi ng pl anes of el evat i on.

Ther e ar e var i ous met hods of gat her i ng t hi s i nf or mat i on

whi ch wi l l be i l l us t r at ed and expl ai ned i n t hi s book . I t

wi l l be neces s ar y t o have knowl edge of geomet r y and a good

unde r s t andi ng of mat hemat i c s i n or der t o pl ot and cal cul at e

i nf or mat i on gat her ed by t he pr ac t i cal s ur vey.

Exper i ence and pr ac t i c al knowl edge can onl y be gai ned by

ac t ual l y car r y i ng out t he met hods and pr ocedu res des c r i bed

i n t he f i e l d.

The re ar e t wo bas i c met hods of l and meas ur ement i n bui l di ng

Pl ane Tabl e Sur veyi ng and Chai n Sur vey i ng, t hes e wi l l be

di s cus s ed and i l l us t r at ed mor e f ul l y i n t he f ol l owi ng pages

of t hi s book.

Ot her met hods i nc l ude t he us e of t he Theodol i t e whi ch i s

us ed f or meas ur i ng hor i z ont al and ver t i c al angl es . Thi s i s

us ed mai nl : y i n Ci v i l Engi neer i ng wo r k i . e. r oad

cons t r uc t i on et c . wher e gr eat er l and mas s es and di s t ances

ar e i nvol ved.

Over l ar ger ar eas of l and t he cur vat ur e of t he ear t h' s

s ur f ace wi l l have t o be t aken i nt o account and i s known as

Geor ' i et i cSur vey i ne; . I t i s us ed i n Or dnance Sur vey wor k and

i s a s pec i al i s ed br anch of l and s ur vey wor k.

2


25/34

B O O K I N G

Ther e ar e t wo f or ms of booki ng down l evel r eadi ngs ,

Col l i mat i on al s o known as Hei ght of I ns t r ument and Ri s e and

F al l met hod.

R i s e F a l l M e t h o d

Us i ng F i g. l . t o i l l us t r at e t hi s met hod t he r eadi ngs t aken

by t he l evel ar e ent er ed i nt o col umns of ei t her Ri s e or Fal l

i . e. t he r eadi ng A dat um i s ent er ed i nt o t he back s i ght

c ol umn wi t h r eadi ng B ent er ed i nt o t he f or es i ght col umn.

As B i s smal l er t han A t hi s denot es a Ri s e and t he di f f e r ence

i s ent er ed i nt o t he Ri s e col umn and r ecor ded as s uch wi t h a

r educed l evel r eadi ng ent er ed by addi ng t o a dat um f i gur e

of 100. 00. f or l evel at B.

Any i nt er medi at e Si ght s ar e ent er ed i nt o t he appr o p r i at e

c ol umn wi t h r educed l evel s accor di ngl y. Di s t ances and

Remar ks Col umns ar e used t o r ecor d change poi nt s and l evel

poi nt s et c. Thi s met hod makes i t pos s i bl e t o check each page

by addi ng t he Ri s e col umn and Fal l col umn, t he di f f erence

shoul d equal t he di f f er ence bet ween t he backs i ght and

f o r es i ght col umn as i l l us t r at ed bel ow.

R I S E

F A L L M E T H O D

S A C

jA/T[J:(

rcRE -

R I S E

/ JJLL

RlIJ/la~

/JIS1~E

RlMllRKS

I{H-IT

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,uy£L

2-00

/00-00

; 1 D c : Iv

M

k t / c l .

0-54

/ 40

/0/4{p

(B )Chq~ t'-

P o ; I / .

2-30

;.70

{)·60

lo.2-0~

rq

2-$0

/-/0

I t;O ·Q6

(q)

J-60

o - s o

100 '/0

(£)ck e 8 7

/60

,2-00

0-4 )

q 9-7~

e r

5-90

(0/,,-

2-06

(31-

/00-00

--

9Cj-7{

t 9 -IIf


26/34

C O L L I M A T I O N M E T H O D

C o l l i m a t i o n M e t h o d

Agai n us i ng F i g . l . t o i l l us t r at e t hi s met hod t he

s ucceedi ng r eadi ng i s subt r ac t ed f r om t he l as t cal c ul at ed

c o l l i mat i on hei ght i e r eadi ng at A i s hei ght of i ns t r ument

bei ng 102. 00 af t er dat um of 100. 00 i s added. Thi s wi l l t hen

gi ve a Reduced l evel at each s t af f posi t i on.

To check add t he back s i ght s and add t he f or es i ght s and

f i nd t he di f f er ence.

By

f i ndi ng t he di f f er ence bet ween t he

l evel of dat um and t he l as t r educed l evel s houl d equal t he

di f f er ence bet ween t he backs i ght and f or es i ght t ot al s .

Al ways check i f pos s i bl e back t o t he dat um poi nt by

t aki ng f l y i ng l evel s t hi s wi l l avoi d a r et ur n vi s i t t o t he

s i t e.

84a:

/I /ffR

RJRE-

/lE/aI/Tor

I?.EO(lCEf)

PIS1 WCE

13£/vt/lRk$

t i I T sasr

y,aIlT

/AI.Jr.ep/ -f~T LErfL.

: 2 . eo

/62

- c o

roa-oo

cJr4T/04/ (It)

/)aIOM.

.,230

o·s4

10)-76

/0/.4

6

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Cha~~

b/iJ

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102·06

C C

2·80

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Ck~t :

1 (,//1 7 .

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t s


27/34

SOURCES OF ERROR I N LEVELLI NG:

I ncor r ec t s et t i ng- up of i ns t r umen t .

1. Bubbl e of f c ent r e when t ak i ng r ead i ng.

2. Movement of s t af f f r om pos i t i on when changi ng l evel

s t at i on.

3.

St af f not hel d ver t i c al l y.

4. Par a l l ax - adj us t .

5.

I n s t r ument knocked or moved dur i ng backs i ght - f o r es i ght

r eadi ng.

6. St af f not pr oper l y ext ended and l ocked.

I NSTRUl mNT ERROR AND

CORRECTION:

Ca) Col l i mat i on er r or ; check bef or e us e and equal i s e s i ght s .

( b) Under s ens i t i ve bubbl e.

( c ) Er r or s i n s t af f gr aduat i on; check.

( d) Loos e t r i pod head.

( e) Tel es cope not par al l e l t o bubbl e t ube - Per manent

adj us t ment .

( f ) Tel es cope not at r i ght angl es t o t he ver t i c al ax i s -

Per manent adj us t ment .

L E V E L L I N G U S I N G A G R I D

Thi s met hod of l evel l i ng i s commonl y us ed and i s s hown

s et out i n F i g. 6.

A

gr i d pat t er n of l Omet r e s quar es i s s et

up over t he s i t e whi ch can be pegged out of f a chai n l i ne

and s et t i ng up t he l evel at s t at i on A and by t aki ng r eadi ngs

i n s equence a, b, c and d et c . an accur at e way of l evel l i ng a

s i t e.

3


28/34

LEVELLING USING GRID

r

0

7

k ,b11

m

~o.

/

f

e

d

-+- - - -~- - - -~- -~~- -~- - - -~- -~-

M A R T I N S l A N E

F i g 6

3~


29/34

L ND ME SUREMENT

B A S I C P R I N C I P L E S

The basi s of al l l and measur ement i s t he use of a base

l i ne and f i xed poi nt s f r om whi ch measurement s can be t aken.

The f ol l owi ng exampl es ar e used as basi c pr i nci pl es f or al l

sur ve; yi ng met hods.

1. RIGHT ANGLED CO-ORDINATES. A

x z

Y

K ~

Poi nt A i s l ocat ed or f i xed by t he di st ance XZ al ong t he

l i ne

XY

measur ed at r i ght angl es t o t he l i ne.

I t i s mai nl y used f or measur i ng boundar i es and bui l di ngs

al ong a chai n l i ne, and i s commonl y known as t aki ng r i ght

angl ed of f set s.

2. FOCAL CO-ORDINATES.

x

y

Poi nt

A

i s l ocat ed or f i xed by measur i ng f r om

X- A

and

Y -A

al ong a

known

chai n l i ne

XY.

Thi s i s qui t e of t en used

f or f i xi ng st at i on poi nt s i n or der t o set up anot her chai n

i . e. XA.

3


30/34

J . ANGULAR CO- ORDI NATES.

A

/

x z r Y

Poi nt A i s l ocat ed or f i xed by measur i ng t he angl es ol

and ' at poi nt s Z and R al ong a chai n l i ne XY. Wher e t he

angl es i nt er sect poi nt A i s l ocat ed. Thi s met hod i s used as

l i nes of i nt er sect i on i n Theodol i t e, pl ane t abl e and compass

sur vey wor k.

4. POLAR CO- ORDI NATES.

Y

Poi nt A i s l ocat ed or f i xed by a known poi nt Z al ong a

chai n l i ne XY and measur i ng t he di st ance ZA t oget her wi t h

angl eo( . A met hod used i n r adi at i ng l i nes on a pl ane t abl e

and l ocat i ng poi nt s gener al l y.

4


31/34

A R E A S V O L U M E S

A R E A S

T r i a n g l e s

A r e a

b a s e x h e i g h t

2

Cor rmonl y used i n sur veyi ng

when l engt hs of si des ar e

of t en onl y val ues

S ~

known , 2

b

A r e a = s s - a ) s - b

) S - C )

a

Lengt hs of t wo si des and i ncl uded known

ane; l e.

b

C

A

c

B

a

A r e a ~ a e s i n L

_ b e

s i n

A

222

T r a p e z i u m

5


32/34

T h e p a r a l l e l o g r a m

a r e a = a x h

D~

a~ ~

Si de8 i nc l uded ~ known but not h.

Ar ea = ab Si n

A

or ab Cos

B

I R R E G U L A R F I G U R E S

S i m p s o n s r u l e

A

a

B

~s sume t hat t he bound r i es ar e par abol i c i n s hape and i s mos t

Eccur at e f or nor mal s ur vey condi t i ons . Can be us ed f or VOLUJ l r : ES

i f ar eas ar e s ubs t i t ut ed f or or di nat e l engt hs .

Odd number of or di nat es .

Even number of s paces .

j ( wi dt h of s t r i p) x [SUP.1 of Lst and l as t or ( hm t e]

( t wi ce s um of ot her odd or di nat es )

( 4 t i mes sur,

of even or di nat es . )

Ar ea

Ar e

x [ y + v ) + 2( +v ) + 4(V2+YA~+Y6)J

_ 1 v7

3

v r . ; er L

3 ~ /


33/34

T r a p e z o i d a l r u l e

sed when t her e ar e any nu _ber of o

r-d

ina

t

s or hei ght s ,

- ay be used f or vol umes i f ar e~s of sect i ons ar e subs t i t ut ed

f or or di nat e l engt hs.

Ar ea = I nt er val ( hal f sum of 1st and l ast or di nat e r emai ni ng

or di nat es. )

P r i s m o i d a l f o r m u l a

Al and A2 ar eas of ends.

Am ar e of m ddl e 08ct i on.

L over al l di st ance bet ween end sect i ons.


34/34

PL NE T LE SURVEYING

Pl ane Tabl e Sur veyi ng i s a oui ck met hod of measur i ng ar eas

or sect i ons of l and. Al l of t he wor k i s car r i ed out on ~ t e

by t he Sur veyor . I t i s not ver y of t en used as a pr act i cal

method of surveyi ng f or r easons of gener al accur acy and

weat her condi t i ons i n t hi s count r y but i t i s ver y usef ul on

mor e dr i er cl i mat es. There ar e f our mai n met hods a) Radi at i on,

b) I nt er sect i on, c) Resect i on, d) Tr aver si ng.

E Q U I P M E N T

To car r y out a Pl ane Tabl e Sur vey you wi l l need a dr awi ng

boar d on an adj ust abl e t r i pod wi t h r ot at i ng head. A smal l

l evel

i e

boat l evel wi t h a compass t o or i ent at e t he survey.

An Al i dade si ght i ng st r ai ght edge, pl umbi ng f or k and pl umb

bob wi t h st at i oner s pi n. Rangi ng pol es, pegs and ar r ows wi t h

st eel measur i ng t ape or chai n. Some of t hese i t ems ar e shown

i n Fig

R A D I A T I O N M E T H O D

To i l l ust r at e t he met hod of Pl ane Tabl e Sur veyi ng Fi g. 2.

shows a t ypi cal bui l di ng si t e t o be sur veyed.

Set up t he Tabl e i n t he cent r e of t he si t e and l evel boar d

ensur i ng t hat al l aspect s of t he si t e can be seen. Locat e al l

ot her poi nt s

i e

change of boundar y l i nes, posi t i ons of

. anhol es, gat es, pol es, t r ees et c. Then usi ng t he Al i dade

si ght ont o t he f i xed poi nt s measur e t he di st ance f r om t he

cent r e peg mar ked on t he gr ound. By usi ng a sui t abl e scal e

dr aw i n t he r adi at ed l i ne on t he paper f i xed secur el y t o t he

boar d f r om t he cent r e pi n whi ch shoul d be di r ect l y pl umbed i n

over t he measuri ng peg on t he gr ound. When car r yi ng out t hi s

pr ocess t he boar d shoul d be cl ocked i nt o posi t i on unt i l

Ei Bht i ngs and measur ement s can be t aken i n sequence A, B, C et c.

f or t he whol e of t he si t e. I f t hi s pr ocedur e i s car r i ed out

car ef ul l y t hen a r epr oduc t i on of t he s i t e wi l l be r ecor ded t o

sc~ e ont o t he boar d.

surveying for engineers

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