Measurement of Landslide Movement with 3D Laser Scanner

ASANO, Hiroki

Erosion and Sediment Control Research Group

Public Works Research Institute

Contents

•Most observation techniques and problem

•Outline of 3D Laser Mirror Scanner

•Attempt of landslide movement measurement

with 3D Laser Scanner

•Result of movement measurement

•Summary

When landslide calamity occursBased on the site situation and the observation value

(ground expansion and contraction meter etc.).

・ The judgment is demanded promptly.

・ Appropriate measures is demanded.Hard measures ： First aid restoration worker

Software measures ： Precaution and shelter 　　　　　　　　　　　　　 recommendation

Observation technique at calamity suddenly

• Watch with CCD cameras

• Watch with ground expansion and contraction meter

Concept chart of watch at calamity

Ground expansion and contraction meter

crack

Storage box

Paling

Principle of ground expansion and contraction meter

Movement of landslide

Inn bar line

Rotation of drum

Record pen

Recording paper

Drum of ground expansion and contraction meter

Example of setting up ground expansion and contraction meter

Insufficient point of ground expansion and contraction meter

•The installation and the measurement are difficult in the place with danger.

•It takes time for the installation (The expansion and contraction meter is one/day).

•The installation and the observation at nighttime are difficult.

laser scanner

landslide

Measurement image of 3D scanner

3D Laser Scanner

Composition of 3D laser scanner

① range finder electronics of the 3D scanner LMS-Z210 laser be②am rotating polygon slow scan ("frame scan") ECP compa③ ④ ⑤tible LPT printer port PC software ⑥ ⑦

Outline of 3D laser scanner

Measurement range ： 2 ～ 350, reflectivity >= 80 % Measurement accuracy ： +/- 2.5 cm,

　　　　　　　　　　 in the worst case 　 +/- 10 cm

Range which can be measured ： 80°×300° total

Beam divergence ： approx. 3 mrad

Eye safety ： Class 1 for the scanned beam

Characteristic of 3D laser scanner• The pulse of the laser beam is launched repeatedly at very sho

rt intervals of time. • Each pulse reflects, the time to returning is measured, and the

distance is measured. • The direction of the laser beam is changed and three-dimensio

nal shape is scanned. ＝ The measurement principle is the same as the machine and the total station etc. of a general light wave measurement.

• A new part is technically a method of scanning• It is possible to measure without setting up the reflection mirr

or .

L

Δ ｔ

Ｌ＝ｃ ・ Δ ｔ　　　　 （片道）

laser scanner

laser pulse t

t

t

laser pulse

mirror

laser scanner

laser scanner

laser scanner

laser scanner

Extension angle of 3mrad

The measurement data displayedto personal-computer

Computational graphic

Computational graphic

Landslide measurement which uses 3D laser scanner

• Geographical features measurement of landslide 　→ Making of ＤＥＭ（ digital elevation model ） 　　→ Making of topographical map 　　　　　　　　　　　　　　　　

• Measurement two or more times →Grasp of displacement situation　　　　 Making of vector chart　　　　 Grasp of range of landslide movement

Ｘ Ｙ

Ｚlaser scanner Overlapping the data is

difficult if there is no points in evaluation.

point （Ｘ，Ｙ，Ｚ） point （Ｘ，Ｙ，Ｚ）

Ｘ Ｙ

Ｚlaser scanner

Ｘ ＹＺ

laser scanner

point （Ｘ，Ｙ，Ｚ）

ＸＹ

Ｚ

point （Ｘ，Ｙ，Ｚ）

laser scanner

Reflection seal

Situation of measurement

laser scanner

Range of measurement

（ top and bottom ） 40°

（ right and left ） 85°

Landslide

Procedure of the measurement data analysis

①The data measurement

②The point data making

④Making of TIN model

⑤Plan and section chart making

③Movement amount calculation

Vector chart

Frequency distribution of measurement error

0

2

4

60

1～ 1

2～ 2

3～ 3

4～ 4

5～ 5

6～ 6

7～ 7

8～ 8

9～

910

～

1011

～

1112

～

1213

～

1314

～

1415

～

(cm)移動量の差

個数

11 月 16日

地すべり末端

11 月 24日

Landslide movement range chartNNN

想定地すべり範囲

データ未取得範囲

11 16月 日

11 24月 日

Summary

①7cm or less roughly against the amount of the movement of 15-20cm.

②The respect grasp of the range of the movement was possible because of overlapping the topographical map before and behind the movement amount.

③The examination is scheduled to be advanced for the improvement of the accuracy in the future.

Finished

Thank you for your attention.