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Introduction
One of the most fundamental surveying
operations is the measurement of
horizontal distance between two points on
the surface of the earth
!here are two basic methods used"
Direct
Indirect
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Introduction
Direct linear measurements are methods
used for determining horizontal distances
with a tape #or chain$ and%or with an
electronic distance measuring instrument
In indirect methods the transit and
stadia or theodolite and stadia are used
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'orizontal Distance
(
)
'()
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*ertical Distance
(
)
*()
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Slope Distance
)
S()(
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+ubits
Distance is one of the most basic
engineering measurements
,arly measurements were made in terms
of the dimensions of the body
Cubits - the distance between the tip of
your middle finger to the elbow
!ypically to measure cords and te.tiles
#another measure was /0 digits or 1 palms$
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2athom
Fathom - distance between the tips of
your middle finger when your arms are
outstretched
!he name comes from the Danish faedn
3outstretched arms3
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2oot
Foot distance from the tip of a man4s big
toe to the heel
Rod - the sum of the lengths of the left
feet of 51 men #516 - /0 ft$
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(pproaches
(pproaches in measuring horizontaldistance 7acing
Optical rangefinders Odometers
!achometry
!aping or +haining ,lectronic Distance Measurement #,DM$
8lobal 7ositioning System #87S$
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7acing
( person can determine their pace by
counting the number of paces necessary
to wal9 a distance that has been
previously measured
( pace is defined as one step
( stride is consider two steps
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+haining
!he most common method used in
determining or laying off linear
measurements for construction surveys
triangulation base lines and traversedistances is often referred to as chaining
2or centuries engineers have measured
distances with ropes lines or cords
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+haining
!he term chaining is a carry:over from
the time when the 8unter chain was used
#51;;4s-5
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8unter +hain
!he surveyor@s chain was called 8unter@s after its inventor
the ,nglish mathematician and astronomer ,dmund 8unter
#56>5-51/1$
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!aping
(ccuratesurveyors@tapes made of
steel or a steelalloy with atypical lengthof 5;; feet or
5;; meterswere used forsurveying
distances
5>=;4s surveyor4s steel tape
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!aping
2or very accurate measurements the
temperature of the tape must be ta9en into
account as well as the tension of the pull
,ach Steel !ape had its own temperature
and tension coefficient which was used to
correct each measurement
Aon-metallic tapes are now common
that are woven from synthetic yarns
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(ccuracy
Pacing; 5%6; to 5%/;;B Ceconnaissance
Odometer; 5%/;;B Ceconnaissance
Taping; 5%5;;; to 5%6;;;B and surveys EDM; E;;0 to 5%F;;;;;B (ll types of
surveying
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Duties of
+haining%!aping Members
!he smallest chaining group could consist
of only two people one at each end of the
tape
!he person ahead holding the zero end
is called the head chainman #bac9 man$
!he other person is 9nown as the rear
chainman #front man$
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7lumb-bob and 7eg
( plumb-bob is used to locate the
measurement point on the tape vertically
above a fi.ed mar9er or to place taping
pins to mar9 tape lengths
,ach end point of a measurement is
mar9ed by placing the plumb-bob string
over the tape
7egs is set out to mar9 the positions
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7eg
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Site SetupStraight ine
( straight line isthe shortest
distance between
two points on a
map or between
two points on the
field
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Site Setup7lacing Canging 7ole
!he correct way to hold a
ranging pole is to 9eep it
loosely between thumb
and inde. finger about 5;
cm above the soil
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Site Setupong Distance Straight ine
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Site Setupong Distance Straight ine
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Site Setupong Distance Straight ine
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Site SetupOver ( Cidge or ( 'ill
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Site SetupOver ( Cidge or ( 'ill
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Site SetupOver ( Cidge or ( 'ill
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Site SetupOver ( Cidge or ( 'ill
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Site SetupOver ( Cidge or ( 'ill
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Measuring DistanceShort Distance
Tip
,ach small division
represents 5mm So if
the nail is positioned two
small divisions after=/>; mm it is mar9ing
=/>/ mm
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Measuring Distanceong Distance
!he head chainman also acts as the
recorder also reads and records the
temperature of the tape
!he rear chainman is responsible for
9eeping the tape in alignment
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Measuring Distanceong Distance
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Stretcherman
2or more precise taping a three-man
party is essential
In addition to the head and rear chainmen
a stretchermanis added
!he duties of the stretchermanare to
apply and to maintain the correct tension
on the tape while the chainmen do the
measuring
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Measuring Distancein ( !all 8rowing +rop
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!aping over evel 8round
If the taping is done over level ground
where there is no underbrush the tape
can rest on the ground
if the distance being measured is greater
than a tape length it is necessary to mar9
the terminal point with a range pole
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)rea9ing !ape
!he term brea9ing tape is used to
describe the procedure for measuring
directly horizontal distance on sloping
ground or through obstacles that do notpermit the use of a full tape length
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Measuring Distancein Steep Sloping (reas
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Measuring Distancein Steep Sloping (reas
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!aping around Obstacles #5$
Ghere an obstruction #eg boulder tree
etc$ lies on the measurement line it will
be necessary to brea9 the tape around the
obstacle
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!aping around Obstacles #/$
'orizontal angles and are used totransform the resulting horizontal lengths
to an eHuivalent horizontal length alongthe measurement line
5 /
F
0 6
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!aping around Obstacles #F$
'orizontal angles are measured using a
compass or are calculated using the
cosine law
(
)+
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Ceview )asic !rigonometry
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Ma9ing !ape +orrections #5$
Off all the measurement method taping is
probably the least automated and most
susceptible to personal and natural errors
!he basic error arise due to
defect in the tape
natural error due to weather conditions
human errors resulting in tape reading errors
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Ma9ing !ape +orrections #/$
( tape supported only at the ends has a
sag in it
Ghen it indicates 5;;;; m actually the
distance measured is less
( steel tape will be longer when it is
warm than when it is cold
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Ma9ing !ape +orrections #F$
(ll tapes are graduated under controlled
conditions of temperature and tension
Ghen they are ta9en to the field these
conditions change
!he tape regardless of the material used
to ma9e it will be either too short or too
long
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Ma9ing !ape +orrections #F$
2or low accuracy surveys the amount oferror is too small to be considered
(s accuracy reHuirements increase
variations caused by the temperature andsag must be computed and used to correctthe measured distance
!ape corrections are typically relativelysmall #ie 5J of the measured distance$but still significantK
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Standardisation #5$
!aping cannot be more accurate that the
accuracy to which the tape is
standardised
!he tape should be standardised by
appropriate authority
!he tape will be return with certificate on
true length and standard condition oftemperature and tension
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Standardisation #/$
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Incorrect !ape 8raduation #5$
actual measurement distance may be
shorter #ll4$ or longer #lLl4$ than measured
due to errors in tape graduation
!he correction is assumed proportional to
the tape length and can be applied to the
total measured length
+orrection factor +
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Incorrect !ape 8raduation #/$
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!hermal ,.pansion #5$
!apes have been standardised#calibrated$ to a specific temperature
(ctual measurement distance may be
shorter #!!o$ or longer #!L!o$ thanmeasured due to thermal e.pansion of thetape
+orrection uses the air temperature duringtaping and may be applied to the totalmeasured length
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!hermal ,.pansion #/$
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7ull%!ension #5$
!apes have been standardised to aspecific tension%pull
(ctual measurement distance may be
shorter #77o$ or longer #7L7o$ thanmeasured depending on the amount oftension applied to the tape
+orrection uses the tension applied duringtaping and may be applied to the totalmeasured length
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7ull%!ension #/$
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Sag #5$
!he actual measurement distance may be
shorter than the measured length due to sagging
of the tape because of its weight or the wind
Sagging is a function of the pull%tension appliedto the tape and the support conditions
!ypically the tape is supported at the ends only
but may also be supported throughout or at
midpoints
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Sag #/$
+orrection is applied to each individual
unsupported length and the total sag
correction #+S!$ is the sum of the sag
corrections for each unsupported tapelength used to ma9e up the measurement
line
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Sag #F$
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Specifications
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Slope #5$
Sloping tape with levelling actual
measurement distance is shorter than the
measured tape length
,levation change across the measurementlength is used to correct measured length
to actual distance
,levation change is measured usinglevelling
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Slope #/$
+orrection factor +
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