advantages of feedback and gps guidance in an … · 2017. 5. 16. · advantages of feedback and...
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ADVANTAGES OF FEEDBACK AND GPS GUIDANCE IN AN ADVANCED TECHNOLOGY AIRBORNE GRAVITY METER
dynamicgravitysystems.com Nigel Brady
DYNAMIC GRAVITY SYSTEMS BACKGROUND
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• Dynamic gravity Systems (DgS) was founded in April 2013 by Daniel Aliod (Electrical Engineer) and Nigel Brady (Geophysicist) with a combined experience of over 50 years in the gravity business.
• Build new airborne, marine and land gravity systems as well as service, repair and upgrade zero length, metal spring based gravity meters (LaCoste & Romberg, Micro-g, ZLS and DgS).
• We have delivered or are currently building 5 new and 3 upgraded dynamic gravity systems
WHY AIRBORNE GRAVITY?
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Advantages • Cover very wide area cost effectively • Consistent coverage (line spacing and altitude) • Access to rough or restricted terrain and coastlines • Data and hardware typically has rapid access to processing and
maintenance personnel after every flight
Disadvantages • High cost of equipment and personnel vs land survey • Logistics and reliability in remote locations • Weather, aircraft and pilot delays • Hardware is exposed to a very high acceleration environment • Lower resolution
WHY AIRBORNE GRAVITY?
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• Sensitive enough for oil, gas, mineral and water exploration • Detection and mapping of faults and other structural geology • Continental shelf mapping • Ice shelf mapping in Antarctica and Greenland • Geoid mapping • Volcanic hazard monitoring
THE ADVANCED TECHNOLOGY AIRBORNE GRAVITY SYSTEM
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• Reliability and Sensitivity of the metal spring gravity sensor. • Full-feedback, magnetically damped system with worldwide range
provides faster response and much lower sensor errors. • Higher accuracy and repeatability is maintained during turbulent flight
conditions (No cross coupling). • No spring tension motor, gearbox or measuring screw required (no
mechanical moving parts aside from the clamp). • Completely redesigned electronics and data acquisition system
integrated with the sensor and temperature controlled. • Data acquisition rate of 10 Hz for airborne system. • GPS timing synchronization for data collection and GPS aided
platform control for airborne system. • Easy system setup and operation. • Price
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A LITTLE HISTORY… THE LACOSTE & ROMBERG AIR DAMPED SENSOR
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AIR SEA II SENSOR SCHEMATIC
Spring
Beam Air Dampers
Test Mass
CPI System
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THE LACOSTE & ROMBERG SENSOR
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THE LACOSTE & ROMBERG SENSOR
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THE LACOSTE & ROMBERG SENSOR
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6800
6802
6804
6806
6808
6810
6812
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6816
6818
6820
-8 -6 -4 -2 0 2 4 6 8
Rela
tive
Gra
vity
(mG
als)
Platform Tilt (Gals)
Gravity versus Platform Tilt in Long and Cross Axes
Long Level (Pitch Axis)
Cross Level (Roll Axis)
THE LACOSTE & ROMBERG SENSOR
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THE LACOSTE & ROMBERG SENSOR
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THE LACOSTE & ROMBERG SENSOR
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DGS FULL FEEDBACK SYSTEM
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DGS FULL FEEDBACK SYSTEM
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DGS FULL FEEDBACK SYSTEM
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-15
-10
-5
0
5
10
15
20
-6
-4
-2
0
2
4
6
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
Long
Lev
el T
ilt (G
als)
Survey Time (Hrs)
Platform Tilt for AT1A Survey
Long Axis
Cross Axis
Cros
s Lev
el T
ilt (
Gals)
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DGS FULL FEEDBACK SENSOR
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DGS FULL FEEDBACK SENSOR
ADVANTAGES OF THE FULL FEEDBACK SYSTEM
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• Beam is locked at the reading line (0 volts) by the feedback electronics
• Effectively reduces cross coupling errors and corrections to zero for virtually all motions
• Eliminates errors caused by non linearity of the beam position when it is non zero
• Eliminates errors caused by imperfections in the counter screw • Reduces significant errors caused by the combination of
platform off level and beam non zero • Data retains high sensitivity of the zero length spring and is
much more repeatable and consistent • Maintains data quality much better in turbulence and during
course deviations
THE DYNAMIC GRAVITY SYSTEM
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THE DYNAMIC GRAVITY SYSTEM
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THE DYNAMIC GRAVITY SYSTEM
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ROSETTA - ANTARCTIC AIRBORNE GRAVITY PROJECT
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Objective: Obtain baseline measurements of the Ross Ice Shelf - Gravity and magnetic data to determine water depth and ocean floor
topography beneath the shelf - Radar, LIDAR and imaging systems to map ice thickness and fine structure
(ICEPOD)
Project: - 36 flights using an LC-130 aircraft operating from McMurdo Station - Ross Ice Shelf = 487,000 km² x 350 m thick on average Science Team: - Lamont Doherty Earth Observatory (LDEO), Columbia University, NY - Scripps Oceanographic Institute, San Diego - USGS, Denver - Dynamic Gravity Systems, Denver - GNS, Wellington
ROSETTA - ANTARCTIC AIRBORNE GRAVITY PROJECT
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ROSETTA - ANTARCTIC AIRBORNE GRAVITY PROJECT
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ROSETTA - ANTARCTIC AIRBORNE GRAVITY PROJECT
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ROSETTA AIRBORNE GRAVITY
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ROSETTA AIRBORNE GRAVITY
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AIRBORNE GRAVITY
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ROSETTA PROJECT GRAVITY PROFILE
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ROSETTA PROJECT GRAVITY PROFILE
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ROSETTA PROJECT EXAMPLE GRAVITY MAP
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210200
Filtered Free air corrected disturbance
190180170160-84
-82
-80
-100
-50
-150
-200
-78
ROSETTA PROJECT – SOUTH POLE
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ROSS ICE SHELF – ANTARCTICA
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SUMMARY - DGS ADVANCED TECHNOLOGY AIRBORNE GRAVITY SYSTEM
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• The system shows dramatic improvement over older zero length spring based systems
• Lab and field results show almost no cross coupling effects and extremely stable, near zero drift gravity in static testing
• The system requires no operator control during flight • The platform guidance improvements allow for drape survey
flights and minimize the effects of aircraft course corrections • Very low setup, calibration and maintenance requirements
compared to other systems • Faster delivery and much lower cost than other systems • Older zero length spring sensors can be upgraded to Advanced
Technology systems
DYNAMIC GRAVITY SYSTEMS
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Contact Information - Web – www.dynamicgravitysystems.com - Email – [email protected] - Phone - +1 303 815-6376 (Nigel Brady) - Address: 7120 W 117th Ave
Denver Colorado 80020 U.S.A.