Geoscience Reference
In-Depth Information
Table 3.1 Precision (M
Δ
, in millimeters) of China's national leveling
Leveling order
First order
Second order
Third order
Fourth order
Tolerance of M
Δ
0.45
1.0
3.0
5.0
Tolerance of M
w
1.0
2.0
6.0
10.0
65°
70°
75°
80°
85°
90°
95°
100°
105°
110°
115°
120°
125°
130°
135°
140°
145°
45°
45°
40°
40°
35°
35°
30°
30°
25°
110°
115°
120°
20°
20°
20°
15°
15°
10°
10°
5°
15°
5°
90°
95°
100°
105°
110°
115°
120°
125°
110°
Fig. 3.16 China's national first-order leveling network
Table 3.2 Precision of leveling lines
Actually measured precision (mm)
<
0.3
0.3 to
0.5
>
0.51
Number of leveling lines
2
285
2
3.2.4 Leveling Route Design, Benchmark Site Selection,
and Monumentation
Design
Technical design signifies to draw up work plans for establishing the most reason-
ably perfect leveling networks or leveling routes on small-scale maps according to
the task requirements and conditions of the survey area. Thus, knowing the survey
area thoroughly and collecting relevant data (like the topographic map of the survey
area, previous leveling results, etc.) will be necessary before design starts. The
leveling lines should be established along the traffic routes with gentle slopes to
which benchmarks can be conveniently leveled. To decrease the chances of being
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