FALCON™ airborne gravity gradiometry provides twice the spatial resolution of other airborne gravity gradiometers
“Resolution” is half the wavelength of the low-pass filter used, or the Nyquist sample rate. This depends on aircraft speed as well as instrument performance, so this comparison is between systems on a Cessna C208, a commonly used aircraft for gravity gradiometry. FALCON surveys are filtered at 300 m, giving a resolution of 150 m (Dransfield and Lee, 2004); FTG surveys are filtered “to remove wavelengths less than 400 to 600 m” (Murphy, 2004) – the figure below shows that this filter actually removes wavelengths less than 700 to 800 m compared to FALCON.
The signal level in the FTG data has decreased by half at about 600 m, giving a resolution of 300 m. Thus FALCON on a fixed wing aircraft has a resolution twice as good as FTG. Better yet, FALCON on a helicopter provides 45 m resolution!
Figure 1. Signal density spectra comparing FALCON (dashed) and FTG (solid) vertical gravity gradient data over the same survey area in South Africa. At wavelengths between 700 m and 300 m, FALCON data is filtered less than FTG data; at longer wavelengths, FALCON sees only slightly more signal than the FTG. These results are from an independent comparison of the two technologies. After Hinks et al. (2004).
Dransfield, M. H. & Lee, J. B., 2004, The FALCON airborne gravity gradiometer survey systems, Lane, R. (ed.), Airborne Gravity 2004 - Abstracts from the ASEG-PESA Airborne Gravity 2004 Workshop, Geoscience Australia Record 2004/18, 15-19.
Murphy, C. A., 2004, The Air-FTG Airborne Gravity Gradiometer System, Lane, R. (ed.), Airborne Gravity 2004 - Abstracts from the ASEG-PESA Airborne Gravity 2004 Workshop, Geoscience Australia Record 2004/18, 7-14.
Hinks, D.; McIntosh, S. & Lane, R., 2004, A comparison of the Falcon and Air-FTG airborne gravity gradiometer systems at the Kokong Test Block, Botswana, Lane, R. (ed.), Airborne Gravity 2004 - Abstracts from the ASEG-PESA Airborne Gravity 2004 Workshop, Geoscience Australia Record 2004/18, 125-134.
FALCON provides 20 times more resolution than airborne gravimetry
FALCON airborne gravity gradiometry has, in a Cessna C208, 150 m spatial resolution along line. Airborne gravimetry surveys are typically filtered at 6 to 7 km wavelength, giving a spatial resolution of 3000 to 3500 m – clearly twenty times poorer resolution than the FALCON airborne gravity gradiometry. (Remember small resolution distances are best.)
The ability of FALCON airborne gravity gradiometry to access the high resolution signal is best shown in the graph in the next section.
FALCON provides the greatest bandwidth and lowest noise
The figure below is derived from Drinkwater et al. (2007). The green curve represents the expected sensitivity of the Gravity Ocean Circulation Explorer (GOCE) satellite launched in March 2009 – GOCE can “see” targets above and to the right of this curve. The blue curve represents the sensitivity of airborne gravimetry based on the analysis by van Kann (2004) – an airborne gravimeter can “see” more than GOCE; in particular a number of targets of interest in oil and gas exploration. The purple curve represents the sensitivity of FALCON gravity - FALCON can “see” all the targets above this curve. It is clear that FALCON gravity is the only system that can see across the entire range of wavelengths of interest in oil and gas exploration – it has the greatest bandwidth by far.
Figure 2
van Kann, F., 2004, Requirements and general principles of airborne gravity gradiometers for mineral exploration, Lane, R. (ed.), Airborne Gravity 2004 - Abstracts from the ASEG-PESA Airborne Gravity 2004 Workshop, Geoscience Australia Record 2004/18, 1-5.
Drinkwater, M. R., Haagmans, R., Muzi, D., Popescu, A., Floberghagen, R., Kern M., & Fehringer, M., 2007, The GOCE Gravity Mission: ESA’s First Core Earth Explorer, Proceedings of 3rd International GOCE User Workshop, 6-8 November, 2006, Frascati, Italy, ESA SP-627, ISBN 92-9092-938-3, pp.1-8.
Simply put, FALCON is the only gravity gradiometry system that was specifically designed for airborne geophysics! FTG systems were designed for use on submarines. This difference is very important because the accelerations (especially vertical accelerations which are critical to high quality gravity data) onboard a fast flying aircraft at low altitude are drastically different from the accelerations aboard a slow moving submarine. Being purpose built for airborne oil/gas/mining exploration FALCON provides superior data resulting from:
- Twice as many complements of accelerometers as FTG systems.
- Twice the separation distance between accelerometers as FTG systems.
- Horizontally oriented accelerometers which greatly reduce noise in airborne applications as compared to FTG systems that have near vertical oriented accelerometers (due to FTG being designed for use on submarines).
- Unique ability to create a measured error map.
- Conforming technology provides all long wavelengths of an anomaly.
- Other technologies available in 1999 (FTG systems rely on technology from the 1980’s).
- Experience & Assets - 1.6 million line kilometers of FALCON flown in 17 countries over the past 10 years. The largest fleet of geophysical aircraft (fixed wing and helicopter) and the largest inventory of airborne gravity gradiometers.
- “Best in class” High Resolution Aeromagnetics (HRAM) acquired as part of every FALCON survey.
- Interpretation capabilities - 20 years of integrated potential fields and seismic interpretation utilizing proprietary software development including a unique simultaneous inversion tool for 3D earth models using gravity, gravity gradiometry, and HRAM data.
- Global presence – Fugro’s network of 275 offices in over 50 countries.
For more information please contact us at: FALCON Inquiries
