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3D and 2D radars for open pit slope monitoring Albert Cabrejo, Product Manager (GroundProbe)
Acknowledgments
From GroundProbe: • Patrick Bellett – Principal Scientist • David Noon – VP Sales & Operations From LisaLabs • Davide Leva – Principal Scientist • Carlo Rivolta - CEO
Introduction and Background
• Real Aperture Radar (RAR) vs Synthetic Aperture Radar (SAR) • Radar dimensionality – 3D and 2D radars
3D-RAR 2D-SAR 2D-RAR
Tactical (targeted) and strategic (broad area) Safety-critical and background monitoring
Rapid-brittle and slow-ductile failures Bench-scale, multi-bench scale, total slope failures
All radars (3D-RAR, 2D-SAR and 2D-RAR) are capable to monitor all these combinations
Each has particular strengths and trade-offs as well
• Balanced comparison of 3D-RAR, 2D-SAR and 2D-RAR • Co-authors (Drs Bellett, Leva and Rivolta)
MONITORING STRATEGIES EFFECTIVE USES OF SLOPE STABILITY RADAR
Monitoring Strategies
Targeted Monitoring
Broad Area Monitoring
• Monitor known risks and hazards
• Highly mobile • Flexible positioning • Safety-critical for
small/large rapid-brittle failures
• Find new risks and hazards
• Often left at crest or mid-slope
• Longer term monitoring
• Safety-critical and background for large slow failures
Targeted and Broad Area Monitoring Systems
3D Real Aperture Radar (RAR) Dish antenna Pencil beam – small spot on the wall Scans a spot in azimuth and elevation Each spot is also sliced in range Highest confidence for targeted area
2D Synthetic Aperture Radar (SAR) Small antennas on rail
Vertical beam – thin stripe on wall Each stripe segmented by range
Fixed view forward Longest range
Highest resolution
2D Real Aperture Radar (RAR) Long antennas
Vertical beam – thin stripe on wall Each stripe segmented by range
Rotates the stripe in azimuth (fast) Broadest area covered per unit of time
3D-RAR 3D Radar sees the world in 3D and generates a radar 3D DTM
Azimuth°
Ele
vatio
n°
3D-RAR
Azimuth°
Ele
vatio
n°
3D Radar sees the world in 3D and generates a radar 3D DTM and projects naturally to front view
3D-RAR with native front view visualisation
3D-RAR with native 3D visualisation
Photograph draped over 3D radar DTM
3D-RAR with native 3D visualisation
Deformation image draped over 3D radar DTM
3D-RAR with native 3D visualisation
Photograph & deformation image draped over 3D radar DTM
2D-RAR
Long antennas
Thin, tall, vertical stripe ~0.5° wide and ~60° tall
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2D Radar with natural plan view image
eg. SSR-FX: 60/180 degrees in 2 minutes Azimuth pixels ~ 0.125°/0.5° Range pixels ~ 0.67 m
180°
180°
Broad area monitoring in Plan view
Broad area monitoring in Plan view
Broad area monitoring in Plan view
2D-SAR
Small antennas Horizontal translation
The 2D-SAR generates a broad beam that synthesizes narrow beams in a fixed field of view.
eg. SSR-SARx bench-scale at 4.5km range
Long range monitoring 2D-SAR
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Long range monitoring 2D-SAR 2mm over 14 days
5mm over 14 days
• 2nd periodical check 6-15 september 2015
Periodic monitoring with 2D-SAR
1st PC 5mm
2nd PC 60mm
Permanent monitoring
Periodic monitoring with 2D-SAR
Conclusions
3D and 2D radars can be used for targeted and broad area monitoring – but each has a strength:
For targeted monitoring of known high risk areas… 3D-RAR provides high confidence for targeted monitoring Front-view display - users can tactically view the slope as if looking
from front-on.
For very broad area monitoring to detect new risk areas …
2D-RAR provides very broad angle coverage quickly Plan-view display - users can strategically view the slope with
reference to other mine geospatial maps (eg. aerial photograph, mine plan, hazards map).
Conclusions
For very long range monitoring … 2D-SAR provides up to 4.5km range over a fixed angle of view
For monitoring slopes with very slow rates of movements… 2D-SAR hardware is easy to relocate and geo-reference so small
movements in-between monitoring periods can be measured.
For some mines, an integrated solution using some or all of
the available radar monitoring technologies (3D-RAR, 2D-SAR and 2D-RAR) together with non-radar monitoring technologies will provide the most comprehensive monitoring strategy
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