Download - Surveying and Measurement
-
8/11/2019 Surveying and Measurement
1/51
-
8/11/2019 Surveying and Measurement
2/51
Levelling
The general term applied to any of the
various processes by which elevations of
points or differences in elevation are
determined.
-
8/11/2019 Surveying and Measurement
3/51
Levelling
To measure the difference in height (H)
between two points and !" vertical rods are
set up at each of these two points and a level
somewhere between them. The height difference between and ! is the
difference between the rod (staff) readings.
-
8/11/2019 Surveying and Measurement
4/51
#nce the elevation of a point is
determined" that point can be used for
determining the elevations of other points.
-
8/11/2019 Surveying and Measurement
5/51
-
8/11/2019 Surveying and Measurement
6/51
Some $efinitions (%)
Levelling surveying operation carried out todetermine the elevation of points or to find the differencein elevation of points
Spirit Level/Engineers Level surveying instrumentused to carry out levelling
Backshot (BS) sighting with a level bac' to a pointof 'nown elevation
Foreshot (FS) sighting with a level to determine theelevation of a point
Turning Point point at which you have establishedan elevation with S and on which you will subseuentlyta'e a !S
Intermediate Shot foreshot to a point at which youwant to 'now the elevation but which will not be used asa turning point
-
8/11/2019 Surveying and Measurement
7/51
Some $efinitions (*)
Peg Test Surveying operation carried out to determineif the levelling bubble and telescope line+of+sight areparallel
Elevation o Instrument (EI) ,levation of the
telescope cross+hairs Balancing shots ttempt when doing a levelling
survey to 'eep the lengths of S and !S at any giveninstrument setup as close as possible.
!losure Error $ifference in elevation determined fromthe levelling survey and the 'nown elevation of abenchmar'.
-
8/11/2019 Surveying and Measurement
8/51
The -se of Levelling
To design highways" railroads" canals" sewers"
water supply systems etc" having grade lines
that best conform the eisting topography"
To lay out construction pro/ects according toplanned elevations"
To calculate volume of earthwor's and other
materials"
To investigate drainage characteristics of an
area" etc.
-
8/11/2019 Surveying and Measurement
9/51
The ,uipments 0
1od (Staff) (%)
-
8/11/2019 Surveying and Measurement
10/51
The ,uipments 0
1od (Staff) (*)
2hiladelphia 1od (front)
2hiladelphia 1od (rear)
$ouble faced levelling
rod
-
8/11/2019 Surveying and Measurement
11/51
The ,uipments 0
1od Level and Tripod
-
8/11/2019 Surveying and Measurement
12/51
3arrying and Setting -p a Level
lways carry it in the container.
Screw the head snugly on the tripod.
or bull eye4s bubble" alternately turn one screw
and then the other two.
#n side+hill setups" place one leg on the uphill
side and other two on the down hill side.
-se hand level to chec' for proper height of thesetup before precisely levelling the instrument.
vial
-
8/11/2019 Surveying and Measurement
13/51
3arrying and Setting -p a Level
-
8/11/2019 Surveying and Measurement
14/51
3arrying and Setting -p a Level
-
8/11/2019 Surveying and Measurement
15/51
2ond !ubble
5hen pond bubble is centred the instrument4sstanding ais is approimately vertical.
The compensators in the instrument ta'e overand ad/ust the optical Line of 3ollimation so that
it is hori6ontal. 5hen the instrument is rotated the
compensators ensure that a hori"ontal plane ocollimationis swept out.
-
8/11/2019 Surveying and Measurement
16/51
#utomatic Levels
fter the pond bubble
is manually centered"an automatic
compensator levels the
line of sight" and 'eepsit level.
-
8/11/2019 Surveying and Measurement
17/51
utomatic Level
-
8/11/2019 Surveying and Measurement
18/51
,+type Levelling Staff (%)
-
8/11/2019 Surveying and Measurement
19/51
,+type Levelling Staff (*)
%.788%.7%8%.7*8%.798
%.79*
-
8/11/2019 Surveying and Measurement
20/51
,+type Levelling Staff (9)
%.%88%.%%8
%.%*8%.%98
%.%99
-
8/11/2019 Surveying and Measurement
21/51
3ommon ,rror Sources
Level rod not vertical
Levelling rod not fully etended or
incorrect length
Level instrument not level
:nstrument out of ad/ustment
,nvironment + wind and heat
-
8/11/2019 Surveying and Measurement
22/51
Suggestions for ;ood Levelling
nchor tripod legs firmly
3hec' the bubble level before and aftereach reading
Ta'e as little time as possible between !Sand S
Try to 'eep the distance to the !S and the
S eual 2rovide the rod person with a level for the
rod
-
8/11/2019 Surveying and Measurement
23/51
,limination of 2aralla
2aralla is the apparent movement of the
image produced by movement of the
observer
-
8/11/2019 Surveying and Measurement
24/51
Types of Levelling =ets
#pen leveling nets
3losed loop leveling nets
height
kno$n
-
8/11/2019 Surveying and Measurement
25/51
Types of Level>ng =ets
3losed lin' or closed connecting leveling nets
Leveling between two points is performed in two
steps0 forward (HAB) and bac'ward (HBA).
The height differences"HAB
andHBA
shouldbe theoretically eual.
HAB - HBA d
height
kno$n
height
kno$n
-
8/11/2019 Surveying and Measurement
26/51
HPC MethodHeight of the Plane of Collimation Method
:t consists in finding the elevation of the
plane of collimation for every set up of the
instrument and then obtaining the reduced
levels (1L) of point with reference to therespective plane of collimation.
The ?23 method is generally used in
profile levelling and in setting out levels forconstructional wor'.
-
8/11/2019 Surveying and Measurement
27/51
HPC MethodHeight of the Plane of Collimation Method
Same staff position as last reading
therefore the same row =ew staff position therefore a new row
?23 @ 1educed Level (1L) A !S
1L @ ?23 + S
1L @ ?23 + :S
-
8/11/2019 Surveying and Measurement
28/51
!L%SE&'L%%P LEELI* !%+P,T#TI%
!ollimation +ethod
-od -eadings (m)Bench+arks
&istance(m) BS IS FS
!ollimation.eight
.eights !orrected.eights (m)
/
*
9
B
C
D
E
F
/
B8
F8
E8
C8
D8
E8
FB
B*
*.%BE
%.D%9
%.8E7
9.BC*
8.9%B
8.*E%
*.EBC
8.DF*
8.B7%
*.9%*
8.*FD
8.%E7
9.C7F
%.8C*
%.B*9
*.7C9
%*F.D*%
%*7.EB9
%*F.C%8
%9%.DED
%9%.F%%
%*F.BFB
%98.%EE
%*7.B9D
%*D.BEB
%*F.%98+%
%*E.B9%+*
%*F.**B
+9
%9%.B7E+B
%*F.*%9+C
%*E.B9*+D
%*F.ECB+F
%*D.BF9+7
/012343
%*F.%*7
%*E.B*7
%*F.**%
%9%.B79
%*F.*8F
%*E.B*D
%*F.EBD
/012343
L @ B7D m !S@%*.989 %*D.BF9 G %*D.BEB @ 8.887 m
3hec' 0 !S+ S @%*.989 G %*.*7B @ 8. @ 8.887m
-
8/11/2019 Surveying and Measurement
29/51
HPC MethodHeight of the Plane of Collimation Method
-
8/11/2019 Surveying and Measurement
30/51
-
8/11/2019 Surveying and Measurement
31/51
-
8/11/2019 Surveying and Measurement
32/51
!alculation checks
S + !S @ %st 1L + Last 1L
:S A S A (1Ls ecept first)@ (each ?23 number of applications)
!heck +isclosure
llowable Misclosure @ H C= mm. (I1ule of ThumbI)
5hen calculations are chec'ed andif the misclosure is allowable
$istribute the misclosure.
Simple check
Full check
-
8/11/2019 Surveying and Measurement
33/51
1ise and all Method
:t consist in determining the difference of levelbetween consecutive points by comparing eachpoint after the first with that immediatelypreceding it.
The difference between their staff readingindicates a rise or a fall according as the staffreading at the point is smaller or greater thanthat preceding point.
The 1L of each point is then found by addingrise or subtracting fall to or from the 1L.
The 1 method provides complete chec' on :S.
:t is commonly used for differential levelling.
-
8/11/2019 Surveying and Measurement
34/51
!L%SE&'L%%P LEELI* !%+P,T#TI%
-ise 5 Fall +ethod-od -eadings (m) &. (m)Bench
+arks
&istance
(m) BS IS FS -ise (6) Fall (')
.eights (m)
/
*
9
B
C
D
E
F
/
B8
F8
E8
C8
D8
E8
FB
B*
*.%BE
%.D%9
%.8E7
9.BC*
8.9%B
8.*E%
*.EBC
8.DF*
8.B7%
*.9%*
8.*FD
8.%E7
9.C7F
%.8C*
%.B*9
*.7C9
%.DCD+%
8.E79+%
9.*E9
+%
%.9**+*
8.D77+%
9.*FB+%
8.EF%+%
*.*E%+%
/012343
%*F.%*7
%*E.B*7
%*F.**%
%9%.B79
%*F.*8F
%*E.B*D
%*F.EBD
/012343
L @ B7D m !S@%*.989 S@%*.*7B @ E.8BB @ E.89C
3hec' 0 !S+ S @%*.989 G %*.*7B @ 8.887 1:S,+ LL @ E.8BB + E.89C @ 8.887
-
8/11/2019 Surveying and Measurement
35/51
1ise and all Method
-
8/11/2019 Surveying and Measurement
36/51
1ise and all Method
all @ S + !S
all @ :S + !S
1ise @ !S + S1L @ 2revious 1L A 1ise
1L @ 2revious 1L + all
-
8/11/2019 Surveying and Measurement
37/51
-
8/11/2019 Surveying and Measurement
38/51
3ollimation ,rrorTwo 2eg Test
The trueheight difference" hT
The visi7leheight difference" h
S%@ S
%4A and
S*@ S
*
4 A
?ori6ontal
Line of sight
!
d
S%
S%4
S*
S*4
L J *
L
L J *
hT @ S%4 + S*4
@ S% + S*h
h @ S%4+ S*4 @hT
h @ (S%4A ) + (S*4 A )
Since the instrument
is the same distancefrom both staff
positions and the
errors are eual
and cancel out.
-
8/11/2019 Surveying and Measurement
39/51
3ollimation ,rrorTwo 2eg Test
?ori6ontal
!
S9
S94
SB
SB4
L J %8L
:f =#T then the error is @
The visi7leheight difference!ut the trueheight difference
:f h @ hT then the instrument is #K
(S% + S*) + (S9 + SB) J L mm J m
h @ S9 + SBhT @ S% + S*
-
8/11/2019 Surveying and Measurement
40/51
3ollimation ,rrorTwo 2eg Test
2lace two pegs about L @ 98m (to B8m) apart. Set up level midway between the two pegs. 1ead staff on each peg" and calculate true
height difference . Move level about L J %8 @ 9m (or Bm) beyond
one of the pegs. 1ead staff on each peg again" and calculate
height difference.
3ollimation ,rror" @ difference in the differencesand is epressed as a number of mm per L m
-
8/11/2019 Surveying and Measurement
41/51
3ollimation ,rrorTwo 2eg Test
cceptable errors -ren and 2rice %mm per *8m 5impey Bmm per C8m
Test should be carried out regularly.
-
8/11/2019 Surveying and Measurement
42/51
?ori6ontal
Line of sight
!
d
S%S*
L J *
L
L J *
?ori6ontal
!
S9
SB
L J %8L
3ollimation error" @ (S% + S*) + (S9 + SB) J L" mmJm
-
8/11/2019 Surveying and Measurement
43/51
2834 m 249 m
2:38 m
02;09 m
# t$o peg test gave the ollo$ing results