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Comparison of Ground Magnetic and

Low Altitude Aeromagnetic Data

R. S. BellGeophysicist & geoDRONEologist

September 29, 2017

SEG Near Surface Technical Section

International Geophysical Service, LLCTel: 303-462-1466 e-mail: rbell@igsdenver.com www.igsdenver.com

SEG 2017 Annual Meeting Post-Conference Workshop

Drones Applied to Geophysical Mapping

mailto:rbell@igsdenver.com

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Objective

Assess data fidelity as well as applicability

of drone based magnetometry using a off-

the-shelf small UAS and the prototype of

the MFAM based MagArrow magnetometer

made by Geometrics, Inc.

Our “standard” were data ground magnetic

survey data acquired using a Geometrics

G-859 Cesium Magnetometer a.k.a. “the

Mineral Mag”.

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G-859 SpecificationsOperating Range: 20,000nT to 100,000nT

Noise: 20,000nT/m

Temperature Drift:

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The MagArrow

prototypeweight: 2.3 kg ( 5.1 lb)

Power – 2.5 W per Sensor

Weight – Less than 2 lbs.

15 cm3 sensor elements

Sample Rate – 1000 Hz.

Sensitivity – 0.001 nT/√Hz

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The sUAS Specifications

Make / model: DJI Matrice 600 Pro

UAV type: X-6 (hexacopter)

MTOW: 34.2 lbs

Lift capacity @ msl: 12.2 lbs

Horizontal speed: 0 to 40 mph

Operational ceiling: 14,750 feet

Max wind speed resistance: 18 mph

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The sUAS Specifications

Make / model: DJI Matrice 600 Pro

UAV type: X-6 (hexacopter)

MTOW: 34.2 lbs

Lift capacity @ msl: 12.2 lbs

Horizontal speed: 0 to 40 mph

Operational ceiling: 14,750 feet

Max wind speed resistance: 18 mph

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The sUAS Fly by Test

~1.1 nT

~2.1 nT

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The sUAS start up noise test

• The G-859 sensor was placed 1 meter from center of sUAS

• Operator initiated start up and lift off sequence of aircraft

• Once flight altitude was achieved he flew away from site

Test sequence for

camera gimbal

lift off

> 10 nT

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Comparison of MFAM data with Ground Magnetometer Data

Geometrics G-859

Sensor 1 Sensor 2

MFAM (MagArrowTM) GPS Line locations

Data are raw total magnetic intensity (TMI) data. The

data have not been corrected or leveled.

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UAS Magnetometry Example – Landfill

line separation: 10 m

UAV altitude:

Block 1 & 2: 15 m AGL

Block 3: 20 m AGL

MagArrow altitude:

Block 1&2: 11.5 m AGL

Block 3: 16.5 m AGLFlight Path

superimposed

on 1m DEM

FB-1

FB-2

FB-3

500 m

50

0 m

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Observed Total Magnetic Intensity (TMI)

3 flights x 15 minutes per flight

Total time on site: 2.5 hours

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RTP Total Magnetic Intensity

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CVG of RTP Total Magnetic Intensity

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CHG of RTP Total Magnetic Intensity

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Ground Survey - Total Magnetic Intensity (raw)

Sensor altitude: 2.3 m AGL

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Total Magnetic Intensity (raw)

Ground Survey

UAS Survey

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Summary & Conclusions

➢ The ground survey required 2 days to complete while

the UAS survey was accomplished in 0.5 days.

➢ The UAS magnetic data compare very well with the

ground magnetic data. No lag corrections were

needed to geo-reference the airborne survey results.

➢ The UAS was test flown at a sensor altitude of 6.5

meter AGL but the pilot was not comfortable with

flying so low. Nevertheless, it was clear that one

could safely fly a UAS survey such that the magnetic

field sensor was at the altitudes typically used for

ground survey.

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