2-11 2 PREPARATION FOR MEASUREMENT
lPrism type-2 (Normal prism)
lPrism type - 3 or 5 (Prism unit A2/A3)
(Example)
In case Prism constant value (C) = 0mm, Prism inclination = 20°, Measuring distance = 100m by Prism
type-2 :
lDistance error is :
From the graph prism type-2, the distance error shows in increasing range quantity 2.5mm along
curved line of C=0 when prism inclination is 20°.
lAngle error is :
From the graph prism type-2, along curved line of C=0 with prism inclination of 20°, find angle error
quantity (14.2mm) and calculate angle er ror by the following formula.
C=40
C=30
0
30
20
10
22
14
6
-2 0
C=0
( mm )
5
4
2
0
( mm ) C=0
C=30
C=40
6
3
1
-1 30
20
10
0
Distance Measuring error Angle measuring error
Inclined angle (degree) Inclined angle (degree)
Increasing
distance
range Angle error
range
2
18
4
C=30
C=20
C=0
C=20
C=30
10 20 30
-1
0
1
2
3
4
0
C=0
-4
0
8
12
010 20 30
( mm
Increasing
distance
range
Angle error
range
Distance Measuring error Angle measuring error
Inclined angle (degre e) Inclined angle (degre e)
( mm)
Angle error =
Angleerror range
Measuring dis cetan
-------------------------------------------- ----------
-1
tan
=14.2
100x103
--------------------
-1