Case study by SPH Engineering · Magnetometry · Pipelines
MagNIMBUS vs MagArrow: two drone magnetometers over buried pipelines
Researchers at CNR IREA in Italy flew two drone magnetometer systems, SPH Engineering's MagNIMBUS and the Geometrics MagArrow, over the same buried steel pipelines on the same DJI M300 RTK. Both found the pipelines. The study shows a trade-off rather than a single winner.
The challenge
Both systems measure the total magnetic field with scalar atomic sensors, but they mount the sensors very differently. The study set out to see how that affects drone interference, flight stability, vertical gradient quality, noise and survey time.
The two set-ups
- MagNIMBUS. Two QuSpin QTFM Gen-2 sensors fixed rigidly above and below the drone, about 1.7 m apart, sampling at 200 Hz. A radar altimeter handles terrain following, SkyHub runs data logging and payload power, and UgCS plans the flights. Both sensors record at once, so one flight gives the vertical gradient.
- MagArrow. One MFAM sensor hung 3 m below the drone, sampling at 1000 Hz, with height set from a terrain model. The vertical gradient needs two flights at different heights.
Noise
Both systems recorded the same pipeline anomalies. In MagNIMBUS, the sensor 0.5 m from the drone showed oscillations up to about 10 nT, and the one 1 m away up to about 5 nT. MagArrow, 3 m below, stayed under 1 nT. MagNIMBUS data had a clear 50 Hz peak from the drone. MagArrow's distance cut most of that, but its swinging payload added low-frequency peaks at about 1.5 Hz and 0.38 Hz. The pipeline signal sat around 0.05–0.06 Hz, so a 0.1 Hz low-pass filter was applied to both datasets before gridding at 1 × 1 m.
The results
- Both systems mapped two pipeline trends: a stronger central NE–SW one and a northern E–W one.
- MagNIMBUS gave a sharper vertical gradient, because both levels were measured at the same time in one flight.
- MagArrow gave cleaner raw signals, but its two-flight gradient was smoother and less consistent.
- MagNIMBUS showed heading error because the drone turned between lines. MagArrow flew at fixed yaw and avoided it, but its gradient was sensitive to mismatches between the two flights.
The researchers did not name a universally better system. A rigid dual-sensor set-up gives a one-flight gradient but picks up more drone noise. A suspended sensor is quieter but needs repeat flights and careful alignment. The right choice depends on the survey goal, the gradient detail needed, site conditions and time on site.
Where this applies in India
- mapping buried steel oil, gas and city gas pipelines before excavation;
- locating steel water mains and other ferrous services across open land;
- choosing a magnetometer set-up for a specific survey goal;
- sensor comparison work at geophysics departments and research institutes.
SPH Engineering's magnetometer training is also available through HobiTech.
The equipment, available from HobiTech
| Magnetometer | MagNIMBUS by SPH Engineering |
| Onboard computer | SkyHub by SPH Engineering with the SkyHub MagNIMBUS software |
| Flight planning | UgCS - Drone Flight Planning Software |
| Compared system | Geometrics MagArrow, tested in the study. HobiTech does not sell it. |
| Drone | DJI M300 RTK was used in this study. Ask us for current compatible drones. |
Case study by SPH Engineering, published March 2026, based on the report "Advances in Magnetic UAV Sensing, a Comparative Study of the MagNIMBUS and MagArrow Magnetometers". This page summarises it in our own words; the research was carried out by CNR IREA, not by HobiTech. Read the original case study on SPH Engineering ↗
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