Simulation for a volcano monitoring network Rainer Mautz ETH Zurich, Institute of Geodesy and...

Simulation for a volcano monitoring network

Rainer Mautz

ETH Zurich, Institute of Geodesy and Photogrammetry

November 22nd, 2008 Session 9: Natural hazards and risks

1. Motivation

2. Positioning Algorithm

3. Simulation Setup

4. Simulation Results

5. Conclusion & Outlook

Contents

Motivation Positioning Algorithm Simulation Setup Simulation Results Conclusions & Outlook

Volcanoes experience pre-eruption surface deformationReason: internal magma pressure cause surface bulge

displacements direction: upwards and outwards horizontal: radial pattern up to 10 cm vertical: uplift of 4 - 6 cm / year (typical) area: over 10 km2

goal spatially distributed position based monitoring system for early warning positioning for spatio-temoral referencing of additional sensors e.g. seismicity, geothermal, gravity, geomagnetic data

1. Motivation

Mount St. Helens, Washington


SAR interferometry: update rate 35 days Geodetic GNSS: expensive, energy consuming

Feasibility of a positioning system with deployed location aware sensor nodes

1. Motivation

tiny nodes low cost battery-powered self positioning ranging capability high density

short range – low power


1. Motivation


GPS (anchor nodes)

tiny nodes

inter-node distances

Tiny Node GPS Station

Principle of Wireless Positioning: Multi-Lateration


known node

unknown node

range measurement


Iterative Multi-Lateration:


Initial anchors

Step 1:

Step 2:

Step 3:

becomes anchor

becomes anchor

becomes anchor


Ambiguity problem when creating the smallest rigid structure

1

32

4

5

1

32

4

5’

1

32

4

5(a) (b) (c)

1

32

4

5

1

32

4

5’

1

32

4

5(a) (b) (c)



Positioning Strategy

find 5 fully connected

nodes

free LS adjustment

return refined coordinatesand standard variations

return local coordinates

failed

no

input ranges

achieved

input anchor nodesyes

volume test

ambiguity test

assign local coordinates

Expansion of minimal structure(iterative multilateration)

Merging of Clusters(6-Parameter Transformation)

Transformation into a reference system

Coarse Positioning

anchor nodes

available?

failed

achieved

failed

achieved

Creation of a robust structure



Object of study: Sakurajima

Stratovolcano, summit with three peaks, island 77 km2

1117 m height

extremely active: strombolian, plinian

densely populated: Kagoshima, 680.000 on island 7.000

monitored by Sakurajima Volcano Observatory(levelling, EDM, GPS)

3. Simulation Setup

Landsat image, created by NASA


Data provided by Kokusai Kogyo Co. Ltd

3. Simulation Setup

Sakurajima Mountain – Digital Surface Model

10 x 10 m grid

Central part of volcano

Area 2 km x 2.5 km


Parameters for Simulation

Parameter Default Value Range

Number of tiny nodes 400 100 – 1000

Number of GPS nodes (anchors) 10 1 – 5 %

Maximum range (radio link) 400 m 200 – 500 m

Inter-nodal connectivity 10 4 - 12

Range observation accuracy 1 cm 0 – 1 m

Node distribution grid / optimised

3. Simulation Setup


400 nodes on a 100 m x 125 m grid. 1838 lines of sight with less than 500 m



Optimised positions. 5024 lines of sight with less than 500 m



200 250 300 350 400 450 5000

100

200

300

400

maximal range [m]

conn

ecte

d no

des

200 250 300 350 400 450 5005

10

15

20

25

30

maximal range [m]

rang

es p

er n

ode

Maximum radio range versus number of positioned nodes


Maximum radio range versus number of range measurements


Number of located nodes in dependency of the number of anchor nodes

Number of anchors

Anchor fraction

Number of located nodes

Success rate Number of ranges

3 0.8 % 3 1 % 3

5 1.2 % 191 48 % 3556

10 2.5 % 354 88 % 4553

15 3.8 % 371 93 % 4874

20 5.0 % 400 100 % 5024



Correlation between Ranging Error and Positioning Error

0 0.2 0.4 0.6 0.8 10

0.5

1

1.5

2

2.5

3

3.5

4

noise [m]

mea

n er

rors

/ d

evia

tion

[m]

+ true deviation● mean error (as result of adjustment)



0 100 200 300 4000

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

node number

mea

n er

ror

[m]

XYZP

Mean errors of the X- Y- and Z-components sorted by the mean 3D point errors (P)



Feasibility of a wireless sensor network shown

Direct line of sight requirement difficult to achieve

10 % GPS equipped nodes required

Error of height component two times larger

Position error ≈ range measurement error

Outlook

Precise ranging (cm) between networks to be solved

Protocol & power management

5. Conclusions


End


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Simulation for a volcano monitoring network Rainer Mautz ETH Zurich, Institute of Geodesy and...

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