`

FUNDAMENTALSOFSURVEYI
NG
LABEXERCI
SENO.05

PROBLEM : DI
FFERENTI
ALLEVELI
NG
OBJECTI
VES : Todeter
minetheel
evat
ionofpoi
ntsby
di
ff
erent
ial
lev
eli
ng.

LABEXERCI
SEOUTLI
NE

A. I
NSTRUMENTS&ACCESSORI
ES:

1.DumpyorWy
eLev
el
2.Lev
eli
ngRod
3.HubsorPegs
4.RangePol
es
5.HammerorMal
l
et
6.Chal
k

B.PROCEDURE

1.Desi gnatet hei nit

ialorreferencepoi ntoft hel ev elrout
easBM- 1andthefi
nal or
ter
mi nalpointasBM- 2.
2.Setupandl ev eltheinstrumentatconv enientl ocationalongthegeneral
designatedr out ebetweent het wopoi nts.
3.Takeandr ecor dabacksi ghtonBM- 1.
4.Di recttherodmant omov ef orwardal ongt hel evelroute(notnecessar
il
yina
str
aightlinebet weenBM- 1andt henextpoi nt)andest abli
shTP- 1.
5.Takeandr ecor daf oresightinTP- 1.
6.Tr ansferandsetupt helevel atanothersui tablel ocati
onbey ondTP-1andtake
andr ecordabacksi ghtonTP- 1.
7.Di recttherodmant omov eaconv enientdist anceaheadoft heinstr
umentand
establi
shTP- 2.
8.Takeandr ecor daf oresightonTP- 2.
9.Repeatt hepr ocedur eunt i
laf oresightisf i
nallyt akenonBM- 2.
10.Refertot heaccompany ingsampl etabul ati
onf ortherecordi
ngofobservedfield
data.
`

STA BS HI FS ELEVATI
ON REMARKS

C.COMPUTATI
ONS

1.Comput
ingHei
ghtofI
nst
rumentandEl
evat
ion.
I
ndi
ff
erent
ial
lev
eli
ng,
thef
oll
owi
ngt
woequat
ionsar
erepeat
edl
yused.
a)HI=El
ev+BS b)El
ev=HI–FS

Wher
e:
HI = hei
ghtoft
hei
nst
rumentabov
ear
efer
encedat
um
BS = backsi
ghtr
eadi
ngont
her
ood(
orpl
ussi
ght
s)
FS= f
oresi
ghtr
eadi
ngont
her
od(
ormi
nussi
ght
s)
El
ev = el
evat
ionabov
ear
efer
encedat
um ofapoi
ntsi
ght
ed

2.Ar
it
hmet
icCheck

Tochecktheaccur
acyoftheari
thmet
icalcomputat
ions,addbacksightsas
wel
lasal
lthefor
esi
ght
s.Thedif
fer
encebetweenthesetwosumsmustbeequal
t
othedi
ff
erencei
nelev
ati
onbetweenthei
nit
ialandf
inal
pointsoft
helevelli
ne.

D.REMARKS,
HINTS&PRECAUTI
ONS

1.Toreducetoanegl i
gibl
eamounttheef
fectofcur
vatur
eandrefr
act
ion,
keepthe
back-
sightdi
stanceapproxi
matel
yequalt
oitscorespondi
ngfor
esi
ghtdist
ance.

2.Li
mitfor
esightandbacksightdi
stancetoamaximum of90meter
ssi
ncemost
l
evel
ingrodscannotbereadaccuratel
ybeyondt
hisdi
stance.
`

3. Al
wayskeepthetel
escopebubblecenter
edatinst
antofsi
ghti
ng.Theaccur
acy
oflev
eli
ngdependsonthebubblebeinginthi
sposit
iondur
ingeachrodsi
ghti
ng.

4.Av oi
dreadi
ngtoonearthetoporbott
om ofther
od.Sel
ectsui
tabl
elocati
onsfor
theinst
rumentsothatbacksi
ghtandforesi
ghtr
odreadi
ngswillf
all
between
0.50and1.50m marksofthelevel
i
ngr od.

5. Avoi
dtheuseofalong(ext
ended)rodespeci
all
ywheni
tiswi
ndy
,andt
he
lev
eli
ngrodisnotpr
ovidedwit
har odsupport
.

6.Sincemor etimeisspentatasetupoftheinst
rument
, caremustbeobser vedso
preventsett
lementoftheinst
rumentbetweenbacksightingandforesight
ing
periods.Toguardagainstset
tl
ementoftheinstr
ument ,
suchaswhenwor kingon
softgroundsduri
ngr ai
nydays,t
hetri
podlegsmustbedr i
venfi
rmlyint
ogood
bear i
ngsoil
.

7.Turni
ngpointsshouldhavearoundedorlevel
edt
optogiv
eadef i
nit
epoi
ntof
supportf
orthebottom oft
helevel
ingrod.I
fahuborpegisused,
avoidl
ocat
ing
suchpoint
sonsof tandunstabl
egrounds.

8.Therodshouldbeheldplumbandsteadywhenar
eadi
ngismadeoni
t.
Pref
erabl
y,usearodlev
el t
oassuret
hatther
odwi
llal
way
sbeheldpl
umband
keepfi
ngersofft
hefaceoftherod.

9.Usethepropertensi
onont
hel
evel
ingscr
ews.Theyshoul
dhav
ebear
ingont
he
tr
ipodheadwithoutbei
ngt
oot
ight
.

10.Fornon-pr
eci
sesur
vey
s,r
odr
eadi
ngsmaybemadet
othenear
esthundr
edt
hofa
meter.

11.Thenumberofi nstr
umentset-upswill
dependlargelyontheconfigurati
onofthe
terr
ain,l
engthofthel
evelci
rcuitorr
oute,
andthel engthofsi
ghtdistances.I
tis
besttoselectt
heshortestl
eveloutpossi
blet
or educet heamountofer r
or
closure.