IBIS-L: IBIS-L: An innovative solution for remote monitoring of displacements on slopes and structures.

Georadar
IBIS System

IBIS
Image by Interferometric Survey
A comprehensive family of ground-based Radar
Interferometers for the measurement of displacements and
vibrations

March 2010 All rights reserved to IDS 1

Georadar
IBIS System
IBIS: ground-based interferometric radars

IDS present the IBIS family:
an innovative range of advanced “geodetic” instruments
based on ground-based radar interferometry aimed at
providing accurate measurement of movements over wide
areas.
IBIS products have been designed to address the specific
needs of the civil engineering, geotechnical and mining
markets
This revolutionary approach provides the IBIS users with
accurate remote measurements without requiring any
contact with the target and in almost all weather conditions.


Georadar
IBIS System
IBIS product range
PRODUCTS APPLICATIONS

IBIS - L LANDSLIDE & DAM MONITORING

IBIS - M SLOPE STABILITY IN MINING

IBIS - S STRUCTURE MOVEMENTS

Georadar
IBIS System
IBIS-S: system & application fields

BRIDGE TESTING

CULTURAL
HERITAGES

IBIS-S

INDUSTRIAL FACILITIES

Georadar
IBIS System
IBIS-L: system & application fields

LANDSLIDE MONITORING

DAM MONITORING

IBIS-L

GROUND SETTLEMENTS
MONITORING


Georadar
IBIS System
IBIS-M: system & application field

IBIS-M

SLOPE MOVEMENT MONITORING
WITHIn OPEN PITS MINES


Georadar
IBIS System
Techniques behind the IBIS systems
The IBIS products are based on four well-known radar techniques:

1. Stepped-Frequency Continuous Wave (SF-CW) technique resolves the
scenario in the range direction, detecting the position in range of different
targets placed along the radar’s line of sight;

2. Synthetic Aperture Radar (SAR) allows to obtain 2D high-resolution radar
images by adding to the range resolution (fro the SF-CW), the cross-range
angular resolution
3. Interferometric technique, computes the displacement of each pixels by
comparing the phase information of the radar signal collected at different
times.
4. Persistent Scatterers algorithm (PSInSAR) selects among the whole image
the high quality pixels and estimates the atmospheric artefacts in an
automatic and robust way


Georadar
IBIS System
Stepped Frequency-Continuous Wave
The SFCW radar detects the position in range of different targets placed along the
radar’s line of sight
n-th
range bin

IBIS-S

Range profile
Amplitude

The range resolution of
0.5 m, independent from
the distance.

Distance (m)

Georadar
IBIS System
IBIS-S: 1-dimensional range profiles
Range Profile: one dimensional image with 0.5m range resolution

Welding lines are good
reflective points

IBIS-S installed at the turbine
pillar base (height 60m)


Georadar
IBIS System
IBIS-L & IBIS-M: Synthetic Aperture Radar (SAR)
SAR technique enables the system to provide high cross range resolution
exploiting the movement of the physical antenna along a straight trajectory
(linear scanner)

Using 2 m rail
IBIS-L system obtains
4.38mrad (=0.25deg)
angle resolution

The SAR process of the data, collected during the movement of the sensor
head on the 2 meter track, allows the IBIS-L and M systems to synthesize a
2m antenna whose azimuth beam width is:

λ
Δϕ = = 4.38mrad
2⋅L

Georadar
IBIS System
IBIS-L & IBIS-M: SAR 2-dimensional images
The combination of SAR and SF-CW techniques allows the system to
resolve the scenario into two dimensional pixels
Power Map
Pixel dimension:
• 0.5m in range;
• 1.35m – 4.05m cross range for 300 - 900m range

Optical Image


Georadar
IBIS System
Interferometric capability
The interferometric analysis provides data on object displacement by
comparing phase information, collected in different time periods, of reflected
waves from the object, providing a measure of the displacement with an
accuracy of less than 0.01mm (intrinsic radar accuracy in the order of 0.001
mm.)

TX
First acquisition
RX

ϕ1 λ
d d=− (ϕ 2 − ϕ1 )
4π
TX
Second acquisition
RX

ϕ2


Georadar
IBIS System
Interferometric capability

The displacement is measured in the direction of the line of sight of the system.

To calculate the real displacement is needed to know the acquisition geometry

R dp
h
α d

dp h R The distance R
d= sin(α ) = d = dp ⋅ is measured
sin(α ) R h by IBIS-S


Georadar
IBIS System
IBIS main advantages
The main advantages of the use of IBIS for monitoring are:
possibility to carry out the survey without accessing the land/structure but
installing the IBIS system in its proximity

obtain information from all the area illuminated by the antenna beam: the radar
measures the local displacement of the scenario by resolving it into pixels of a few
square meters

high displacement measurement accuracy, up to 1/10 mm

day-night continuous operation

completely autonomous operation not requiring human intervention

acquisition frequency of the order minutes for IBIS-L, msec for IBIS-S


Georadar
IBIS System
Landslide monitoring

Active earth slide evolving into
an earth flow in the lower part

Very fast movements (m/days)
during re-activation periods


Georadar
IBIS System

DISTANZA DAL VERSANTE [m] 450-1300

APERTURA ORIZZONTALE ANTENNE [gradi] 38

RISOLUZIONE IN RANGE [m] 0.5

RISOLUZIONE IN CROSS-RANGE [mrad] 4.5

ACQUISIZIONI PER ORA - 9

DURATA SESSIONE [ore] 24

IBIS - L
IBIS - L
IBIS-L

IBIS-L System set-up

Georadar
IBIS System

1

0.5

Geocoded quality map Picture taken from the radar location

More than 40.000 measurement points
are identified on the quality map

Georadar
IBIS System
Geocoded cumulative displacement map (1 h)
Geocoded Line Of Sight Displacement Map

[mm]
2

-50


Georadar
IBIS System

[mm]
2

-50


Georadar
IBIS System
Identification of moving portions of the slope

Zona A
Zona B
Zona C
Zona D

[mm]
2

-50


Georadar
IBIS System
Displacement time series
ZONA A - movimento di alcuni punti di misura selezionati
Line Of Sight Displacement Time Series

Mappe di
spostamento
cumulato dopo
24 ore


Georadar
IBIS System
ZONE A - displacement of a few points

Mappe di
spostamento
cumulato dopo
24 ore


Georadar
IBIS System
ZONE B - displacement of a few points

Mappe di
spostamento
cumulato dopo
24 ore


Georadar
IBIS System
ZONE C - displacement of a few points

Mappe di
spostamento
cumulato dopo
24 ore


Georadar
IBIS System

IBIS-M for open-pit mines

Following a 80,000 ton slip
occurred in late 2009 and
the consequent closure of
operations, an IBIS-M unit
was deployed in January
2010 at the Pipeline pit in
Cortez, Nevada, owned by
Barrick.

The IBIS-M system was aimed at providing early warnings and support for
geotechnical evaluation purposes.
After 7 months of rental of the equipment, in July 2010, the IBIS-M unit was
purchased by Barrick.

Georadar
IBIS System

IBIS-M for open-pit mines

DISTANCE FROM THE SLOPE [m] 800 – 1500
ANTENNA BEAM WIDTH [deg] 68
NUMBER OF POINTS - 90.000
0.5
RANGE RESOLUTION [m]
(1.64 ft)
CROSS-RANGE RESOLUTION [mrad] 4.5
SCANNING TIME [min] 5

Georadar
IBIS System
IBIS-M set-up
Dispatch Room
Guardian Software
Shelter (pit rim) 24/7 monitoring for alarms
IBIS‐M basic configuration unit Status alarms/emails
Fully enclosed (HVAC, WiFi) Geotechnical alarms/emails
Mine grid power supply
Backup power (1 day with genset)
IBIS Controller Software
24/7 functioning

Wireless link
+/‐ 200‐300KB VPN, VNC
every 6‐7 mins connections
Engineer’s laptop

Georadar
IBIS System
IBIS-M set-up
Proces sing unit
Dedicated laptop
Sensor unit Pa nasonic CF19
IP65
Power
supply unit
(IBIS and
laptop)
Linear scanner

Base

Shelter

Georadar
IBIS System

Cumulative displacement from 03/02 to 18/02

Georadar
IBIS System


Georadar
IBIS System

Cumulative displacement from 03/02 to 21/09: time series

Georadar
IBIS System
Dam monitoring
Cancano Dam view
Dam characteristics
Dam Type Gravity arch
Location Alpi Retiche - Italy
Dam height (m) 125.5
Crowing length (m) 381

Dam plan

Survey performed with the
Surveying Dept. of Milan Polytechnic


Georadar
IBIS System
Dam monitoring

IBIS-L configuration
• Dam-sensor distance: 400m
• Range resolution: 0.5m
• Angle resolution: 4.7mrad
• Sampling interval: ca. 9 minutes


Georadar
IBIS System
Dam monitoring
Zoom onMap area
SNR dam

dam

rocks


Georadar
IBIS System
Dam monitoring
Dam Power map projected over plan


Georadar
IBIS System
Dam monitoring
Selected pixel L.O.S. displacement – 5 pixel belonging to the dam crown


Georadar
IBIS System
Dam monitoring

Point displacement comparable with dam coordinometer


Georadar
IBIS System
Dam monitoring
Crowining point displacement comparison between
IBIS-L and coordinometer measure

IBIS-L sampling interval: 9min
Pendulum sampling interval: 4hours

Georadar
IBIS System
IBIS Guardian

IBIS Guardian

• Real time processing with automatic
atmospheric corrections
• Alarm generation with user-defined
levels and multiple alarm criteria
• Fully georeferenced outputs
• 3D interactive data handling
• User defined zones for alarm
generation
• Exportability of outputs to GIS and
mine planning software

77

Georadar
IBIS System
GUARDIAN typical output
Displacement Map
- in mm for every pixel
- negative displacements are in approach

Velocity Map
DEM - in mm/h for every pixel

Hazard Map

-Variable number of levels and thresholds
-Automatically updated with the last data
Quality Map
Alarm -Exclude / Differentiation of areas
- Trigger the alarms:
- Values between 0-1 Moving - PC SC REEN
- Reliability of the pixel for
- SMS
distance measurements Stable - EMAIL

March – April 2010

Georadar
IBIS System
Bridge testing: static live load test

Viaducts crossing Forlanini Avenue Bridge beams are good reflecting points
(Milan, Italy)

Static monitoring of a new bridge:
Determination of displacement of the
bridge during a static load test


Georadar
IBIS System

90
B C
A D
80 H
E
F IBIS-S
70 G
installation
SNR (dB)

60

50 Range profile of
40 P2-S – P3-S span
30
0 10 20 30 40 50 60 70
Ground-Range (m)


Georadar
IBIS System

LC1 LVDT
10
displacement (mm)

0

-10 B
D
-20 F
H
-30
0 200 400 600 800 1000 1200 1400
time (s)

Georadar
IBIS System

LC1 LVDT
10
IBIS-S
displacement (mm)

LVDT
0
-8.84
-10
-15.62
-20.50
-20

-30
0 200 400 600 800 1000 1200 1400
time (s)

Georadar
IBIS System

LC2 LVDT
10
IBIS-S
displacement (mm)

0 LVDT

-10 -14.28
-20
-25.20
-30 -32.76

-40
0 200 400 600 800 1000 1200 1400
time (s)

Georadar
IBIS System

LC1, P2-S – P3-S span:
Deformed elastic curve
provided by IBIS-S


Georadar
IBIS System
Bridge testing: dynamic test of bridge span
Measurement objective: comparison with accelerometers, resonance
frequencies and modal shape retrieval

Central arch length (m): 62.5


Georadar
IBIS System
To make a comparison between the
results of IBIS-S system and
accelerometers system 6 corner reflector
were installed at the same position of
accelerometers


Georadar
IBIS System
Bridge photograph and range profile


Georadar
IBIS System
Velocity comparison for Test Point 22
Velocity [mm/sec]

Zoom on the first 15 sec – direct comparison

IBIS-S
IBIS-S
acc

Time [sec]
Velocity [mm/sec]

accelerometer

Time [sec]

Georadar
IBIS System

Frequency analysis
acc comparison on
3000sec
acquisition duration

IBIS-S

Acc detected IBIS-S detected Percentage
frequency frequency error
Hz Hz %
2,617 2,595 0,84
3,164 3,182 -0,57
6,641 6,608 0,50
8,086 8,077 0,11


Georadar
IBIS System
Modal shape obtained by accelerometer data

f = 2.617 Hz f = 3.164 Hz

f = 6.641 Hz f = 8.086 Hz


Georadar
IBIS System
Modal shapes comparison
1.2
Normalized Mode Shape

Accelerometer
IBIS-S sensor
0.6

0.0
f=2.617Hz
-0.6

-1.2
0 23 46 69 92 115
Distance along deck (m)

1.2

Accelerometer
IBIS-S sensor
0.6

0.0 f=3.164Hz
-0.6

-1.2
0 23 46 69 92 115


Georadar
IBIS System
Modal shapes comparison
1.2

Accelerometer
IBIS-S sensor
0.6

0.0
f=6.641Hz
-0.6

-1.2
0 23 46 69 92 115

1.2

Accelerometer
IBIS-S sensor
0.6

0.0 f=8.086Hz
-0.6

-1.2
0 23 46 69 92 115


Georadar
IBIS System
Bridge testing: Cable-stayed bridges
Application goal: dynamic analysis done through ambient vibration testing
(AVT) aimed at:
- Identify the amplitude of the cable vibrations;
- Identify the natural resonant frequencies and the cable dumping
factors
- Evaluate the tension and the operating strain of cables to verify the
correct distribution of loads and the temporal variation of tensions along
the bridge life


Georadar
IBIS System
Advantages in the use of IBIS-S:
- Provide displacement measurements (useful to evaluate the
amplitude of vibrations)
- Very accurate measurement: an order of magnitude higher than
LDV
- No traffic shut-done needed (IBIS can be installed under the
bridge or beside the bridge towers)
- Simultaneuous measurement on a large number of cables
(potentially all cables of each side at once)
- Rapid installation and measurement set-up


Georadar
IBIS System
Geometrical sketch of IBIS-S set-up:

IBIS on the bridge

IBIS below the bridge


Georadar
IBIS System
Olginate bridge (Italy)


Georadar
IBIS System
Olginate bridge (Italy)

IBIS-S set-up

Range Profile
Displacement graph
0,8
Displacements (mm)

0,4
0,0
-0,4
-0,8
-1,2
-1,6
-2,0 Interferometro IBIS-S
0 100 200 300 400 500 600 7 00 800 900 10 00
Time (s)


Georadar
IBIS System
Example: Olginate bridge (Italy)
Comparison with accelerometers
800
Acceleration (mm/s 2)

600
400
200
0
-200
-400
-600
-800
Sensore WR731A Interferometro IBIS
260 270 280 29 0 300 310
Time (s)

500
400
Acceleration (mm/s 2)

300
200
100
0
-100
-200
-300
-400
Sensore WR731A Interferometro IBIS
-500
260 270 280 29 0 300 310
Piezo-electric accel. WR 731A
Time (s)


Georadar
IBIS System
Example: Olginate bridge (Italy) 26
24
22

Frequency (Hz)
Frequency Domain Analysis 20
18

fre que nz a [Hz]
0
10
-1
Interferometro IBIS 16
f = 3.906 n
10 14
12
ASD (mm) 2/Hz

-2
10
-3
10 IBIS 10
8
-4 6
10
4
-5
10 2
-6 0
10
-7
0 1 2 3 4 5 6 7
10
-8
n
n
10

10
-1
0 5 10 15 20 25
Tension
Sensore WR731A
ASD (mm) 2/Hz

-2
10 Cable S09'
10
-3
Accel.
IBIS-S Accelerometer
-4
10
-5
fexp Tension fexp Tension
10
(Hz) (kN) (Hz) (kN)
-6
10
3.906 1883.1 3.809 1790.7
-7
10
0 5 10 15 20 25 7.764 1860.0 7.495 1733.3
Frequency (Hz) 11.720 1883.7 11.470 1804.2
Resonant frequencies
15.630 1884.5
f1 (Hz) f2 (Hz) f3 (Hz) f4 (Hz) f5 (Hz) f6 (Hz)
19.510 1879.2
IBIS-S 3.906 7.764 11.720 15.630 19.510 23.460 23.460 1886.9
Accel. 3.809 7.495 11.470
1880 1776


Georadar
IBIS System
High-rise structures: chimney testing
Measurement objective: measurement of the displacements of the old and new
chimney and identification of their resonance frequencies
Old chimney
New chimney
Chimney high: 183m

Measurement parameters:
maximum range: 300 m
sampling frequency: 50 Hz
range resolution: 0.5 m
distance from the target: ~ 50 m


Georadar
IBIS System
Range profile of the new chimney

T h e rm a l S N R - S u r v 0 2
50

40

30
SNR [dB]

20

10

0

-1 0
0 50 100 150 200 2 50
R an ge [m ]


Georadar
IBIS System
Horizontal displacement Frequency Analysis
New chimney 2 45

40
1.5

Projected Displacement [mm]
35
Point located at the 30
1

[mm/H z]
middle of the
25 X: 0.38
chimney, at a height Y: 20.54

of 121 m 0.5 20

15
0
10
Rbin 266
5
-0.5 0 0.5 1 1.5 2
100 200 300 400 500 600
frequency [Hz]
time [sec] 45
3.5
Rbin 362 40
3
Projected Displacement [mm]

Point located at the 2.5 35

top of the chimney, 2 30

at a height of 172 m

[mm/Hz]
X: 0.38
1.5 25 Y : 22.3 8

1 20

0.5 15

0 10

-0.5 5
Identified frequency: 0.38 Hz 100 200 300 400 500 600 0 0.2 0.4 0.6 0.8 1 1. 2
frequency [Hz]
1.4 1. 6 1.8 2

time [sec]


IBIS-L: IBIS-L: An innovative solution for remote monitoring of displacements on slopes and structures.

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