Application of InSAR for Monitoring Deformations at the … · 2019-05-08 · SELECTED PROJECT...
Transcript of Application of InSAR for Monitoring Deformations at the … · 2019-05-08 · SELECTED PROJECT...
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Application of InSAR for
Monitoring Deformations at the
Kiirunavaara Mine
Karola Mäkitaavola
Britt-Mari Stöckel
Jonny Sjöberg
Stephen Hobbs
Jonas Ekman
Michael Henschel
Anura Wickramanyake
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SUBLEVEL CAVING = GROUND DEFORMATIONS
Ore- body
Hangingwall Footwall
Caved rock
Deformation Zone Fracture
Zone Caving Zone
Fracture Zone
Deformation Zone
Continuous deformations
Discontinuous deformations
Continuous deformations
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KIRUNA
City Hall
LKAB Kiirunavaara Mine
North
City of Kiruna
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ENVIRONMENTAL DEFORMATION CRITERIONStrain limit 3 ‰ horizontally, 2 ‰ vertically
M1
Example: 50 m distance max
15 cm
M2 M2
max
10 cm
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GPS MEASUREMENT NETWORK
North
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PROJECT DESCRIPTION
• Assess the use InSAR technology for LKAB's purposes as a
replacement and/or complement to current GPS measurements
• Further develop the InSAR technology for winter conditions at high
latitudes, aiming at improving precision
• Conduct a technology transfer to LKAB with the goal of LKAB being
able to produce results (deformation maps) in-house from satellite
data SAR
Project
MonitoringSemi-annual
deformation maps
Technology Transfer
Software & procedure
training
Basic theory and research
Supervision (PhD & MSc)
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INSAR MONITORING TECHNOLOGY
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INSAR TECHNOLOGY
• Wide area monitoring (DInSAR)
• Point analysis
– Corner Reflectors (CR)
– Coherent Target Monitoring (CTM)
• All monitoring techniques applied and tested in Kiruna
– Historic analysis conducted initially to confirm applicability
– Development of monitoring program including DInSAR, CTM,
PSInSAR and CR (for areas with little or no backscatterers)
– RADARSAT-2 satellite data used for entire project; 24 day return
period, 3 beams used (later 2 beams)
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MONITORING IN KIRUNA
• CR network installed; 60 + 6
dual corner reflectors at 33
locations
• CTM for natural / artificial
reflectors (mostly existing
infrastructure; > 20 000 points)
• DInSAR deformation maps
• Result delivery every 6 month:
– Satellite imagery
– Deformation maps
– Time series profiles CR & CTM
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SELECTED PROJECT RESULTS
• Accuracy Assessment
– Poor accuracy for N-S deformations due to polar orbit of
satellites
– Line-of-sight as well as E-W and vertical decompositions more
reliable
– Preferred set of 2D decompositions reduced uncertainty further:
• CR: 2 mm in E-W and vertical direction
• CTM: 4 mm in E-W direction; 3 mm in vertical direction
• Monitoring Data
– DInSAR deformation maps for assessing overall trends
– CR time series plots
– CTM "maps" & selected points for time series plots
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CTM "MAP" & SELECTED CTM POINTS
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CTM "MAP" & SELECTED CTM POINTS
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SELECTED PROJECT RESULTS
• Comparison with GPS Data
– Comparison at neighboring GPS and CR points, plotted for the
same time period
– Very good agreement in both trend and magnitude of ground
deformations
– Increased trust-
worthiness in
InSAR results!
-0.14
-0.12
-0.10
-0.08
-0.06
-0.04
-0.02
0.00
2010-03-23 2011-03-23 2012-03-22 2013-03-22 2014-03-22
E-W
De
form
ati
on
(m
)
Date
InSAR CR08
GPS M8
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SELECTED PROJECT RESULTS
• Seasonal Coherence Variation
– Snow layer reduced coherence; fewer suitable winter images
– Good summer-summer coherence; use summer image as
master image to achieve high coherence
• Technology Transfer
– Build-up of knowledge and know-how within LKAB
– High-level & targeted training provided by MDA to LKAB,
including software and hardware tools
• Strain Calculations
– Important to determine location of envirionmental criterion limit
– InSAR CR measurements used to assess location
– Reasonable agreement with GPS; additional fine-tuning required
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STRAIN CALCULATION COMPARISON
Measurement
points
Horizontal strain [‰] Vertical strain [‰]
GPS InSAR (CR) GPS InSAR (CR)
M7-M8 0.79 0.4-0.5 0.49 0.3-0.4
B14-C20 0.67 > 0.7 0.47 0.5-0.6
D50-D53 0.53 0.4-0.5 0.08 0.1-0.2
L8-L10 0.40 0.3-0.4 0.46 0.4-0.5
L10-L14 0.47 0.4-0.5 0.23 0.2-0.3
S13-S15 0.03 0.2-0.3 0.11 0.3-0.4
B14-F51 0.39 0.5-0.6 0.33 0.5-0.6
M8-M12 0.40 0.4-0.5 0.26 0.3-0.4
H13-H12 0.71 > 0.7 1.35 0.6-0.7
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CONCLUSIONS
• InSAR allows measurements over large areas with fewer
measurement hubs (CRs) compared to GPS measurements
• DInSAR deformation maps worked well for identifying trends and
patterns in ground deformations, but dependent on having high
coherence between image pairs
• CR & CTM provided high-precision data for specific points, and
(nearly) year-round coverage
• CTM particularly appealing (no installations needed) but susceptible
to ambiguous phase unwrapping; large number of CTMs help
reducing this uncertainty + supplement with CRs in areas with poor
coverage
• E-W and vertical deformations components satisfactorily analyzed;
not possible to achieve acceptable accuracy for N-S deformations
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RECOMMENDATIONS
• Continue InSAR measurements in Kiruna as a complement to
current GPS measurement – focusing on point analysis (CR & CTM)
• Additional CR should be installed in areas with poor CTM coverage
and poor back-scatter
• Additional work on comparing CR & CTM InSAR data with GPS
measurement, to further "ground truth" the InSAR data
• More work on coherence effects and winter images warranted;
robust methodology for data analysis required
• Evaluate alternative measurement techniques for monitoring of
mining-induced ground deformations, e.g., automated GPS,
automated total station, UAV photogrammetry, UAV LiDAR, etc
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Thanks to: - Jimmy Töyrä & Carlos Quinteiro (LKAB) for paper review
- Wendy Branson & Brad Lehrbass (MDA) for project work & cooperation
- Stefan Buehler & Tore Lindgren (LTU) for academic supervision
- Priya Fernando (EADS Astrium) for project support
- Bo Fjällborg & Anders Berg (LKAB) for project cooperation
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Thank you for your attention