Reference:
Check the additive constant of the distance
The additive distance constant of the instrument is adjusted before delivery. It is
possible that this will deviate over time, use a baseline with a
known precision
distance
to check the additive distance constant. If there is no baseline, perform these
checks as follows.
Caution :
Errors is setting up the instrument and reflective prism or in sighting the
target will influence the additive distance constant. Be extremely careful to prevent
such errors when performing these procedures. Set up so that the instrument height
and the target height are identical. If a flat place is not available, use an automatic level
to make sure the heights are identical.
（
1
）
Find an area of flat ground where two points 100m apart can be selected. Set
up the instrument at point A and the reflective prism at point B, establish a
point C half way between points A and B.
A
B
C
（
2
）
Precisely measure the horizontal distance between point A and point B 10
times and calculate the average value.
。
（
3
）
Place the instrument at point C directly between points A and B and set up the
reflective prism at point A.
（
4
）
Precisely measure the horizontal distances CA and CB 10 times each and
calculate the average value for each distance.
（
5
）
Calculate the additive distance constant as follows
：
K=AB
－
(CA
＋
CB)
（
6
）
If the result is different with the standard constant, please see“24.3 Setting the
Additive and Multiply Constant”.
（
7
）
After set it , you should check it on another baseline.
（
8
）
NOTE: Please user Tripod Mounted Prisms with precision Tribrachs. DO NOT
use prism poles with Bipods or Tripods.
100
Summary of Contents for CST202
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