Topcon AP-L1A - Page 31

2. PREPARATION FOR MEASUREMENT
2-8
 Prism type-2 (Normal prism)
Distance Measuring error Angle measuring error
Inclined angle (degree) Inclined angle
 Prism type - 3 or 5 (Prism unit A2/A3)
Distance Measuring error Angle measuring error
Inclined angle (degree) Inclined angle
(Example) In case Prism constant value (C) = 0mm, Prism inclination = 20
, Measuring distance =
100m by Prism type-2 :
 Distance 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
.
 Angle 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 error by the following formula.
Angle error = tan
-1
Angle error range
Measuring distance
Angle error = tan
-1
14.2
100 10
3













A
ngle
error
range
Increasing
distance
range
Increasing
distance
range
( mm ) ( mm )
( mm )
A
ngle
error
range
( mm )
= 29”