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1. Measurement of Horizontal distance
 Horizontal Distance is the distance Measured
along a horizontal line, regardless of the
elevation of end points.
 Vertical distance is the distance measured along
a vertical line.
 Vertical line is a line passing through a given
point and the centre of the earth.
 Any line perpendicular to a vertical line is a
horizontal line.
 Horizontal line is not a single line. It is a
horizontal plane.

2. Measurement of H.
Distance
There are several methods.
 Pacing
 Odometer on the automobile
 Measuring wheel
 Stadia
 Subtense bar
 Taping/Chaining
 EDM

3. PACING
 Distance = no. of steps X length of a step
 Two methods to calibrate pace length.
1. Determine the average length of a
step by walking a known distance.
2. Adjust the pace length to
predetermined length.
 This is a crude method.
 “Accuracy 1/50”
 Record the distance to nearest m of ft.

4. STADIA
 Set the instrument on one point and hold
the rod on the other point.
 Sight through the instrument and read
the rod where upper and lower stadia
hairs are intersecting the rod.
 Difference between these two readings
is call Stadia Interval.
 Using the Equation D = KS + C,
calculate the distance.

5. 1. Focusing screw
2. Eyepiece
3. Foot screw
6. Tangent screw
7. Circular bubble

6. 4. Horizontal circle
5. Base plate
8. Collimator (sight)
9. Object lens

12.  If the inclined line of sight is necessary,
as shown in the figure, the distance from
the instrument to the rod H, and the
vertical distance V, can be computed by
H = Ks cos2 α + C cos α
V = Ks cos α sin α + C sin α

13. SUBTENSE BAR

14.  Subtense bar is 2m long.
 Set the instrument on one point and
subtense bar on the other point.
 Sight at two targets on the subtense bar
and measure the subtended angle.

15. Taping or Chaining
 Most common surveying method in H.
distance measurements.
 Two persons are needed for taping.
Head tape man and rear tape man.
 Instruments – Tape/chain, taping pins,
range poles, plum bobs, hand level.
 The 1st rule of taping is to keep the tape
along a straight line between two points.
 Head tape man should walk with the 0
end of the tape while rear tape man
remains at the initial point.

16.  The rear tape man should hold a whole foot
mark at his point.
 Head tape man should apply the tention and
he is holding some mark within the 1st foot
mark which is calibrated in tenths and
hundreds of a foot.
 Head tape man should read the tape and
subtract (if it is a subtracting tape) or add (if
it is a adding tape) the value from the whole
foot value to get the distance.
 If the distance to be measured is more than
one tape length, intermediate points must be

17.  In order to avoid mistakes head tape
man should start with 10 pins and rear
tape man should have one pin.
 When proceeding forward, rear tape
man should collect the pin fixed by the
head tape man.
 If this procedure is carried out the
number of pins with the rear tape man is
equal to the number of tape lengths
made.

18.  Some times tapes may be slightly longer
or shorter than their nominal length due
to stretching, imperfect manufacture or
wear.
 Corrections for measurements can be
made using the equation
la/ln = da/dm
la = Actual length of the tape
ln = Nominal length of the tape
da = Actual distance
dm = Measured distance or tape
distance to be laid off

19. EDM
 Two types. Micro wave and Infra red.
 Infrared is common.
 By pressing an appropriate button,
instrument release electromagnetic
waves and the reflector held on the
other point reflects them back to the
instrument. The instrument displays the
distance based on the time taken.