Tensor Gradiometry

Ask us about our full range of software and services for AGG data (and custom code for Magnetic Tensor Data)

  • Software: Intrepid and GeoModeller
  • QC service
  • Solution services including ‘processing’ and ‘interpretation’
  • Software training

Tensor Gradiometry

Intrepid Geophysics develops specific software tools and methods for handling potential field tensor gradiometry data - having spent over five years designing and shipping geophysical tools to properly respect the complete signal type, as well as the component tensors. See our ASEG 2016 Gravity Gradiometry Workshop paper.

In practice, the gravity gradient survey data you may have, likely comes from an instrument built by Lockheed Martin for Bell Geoscience, Bridgeporth, Xcalibur, or CGG (Falcon data). Falcon is a partial horizontal tensor gradient measurement system, while the others are modern systems for measuring Full Tensor Gradiometry (FTG) measurements. Together the groups of data are called Airborne Gravity Gradiometry (AGG).

The next generation of hardware has now been released, for example Enhanced FTG (eFTG). Typically, the larger the inertia of the host aircraft, the better the signal. Also, the newer fully digital electronics present more-stable systems compared with the older analog electronics.

Magnetic gradient survey data are measured by IPHT instrumentation. These data are also supported through calibration and processing via the Intrepid custom software suite.

Processing workflows for Airborne Gravity Gradiometry (AGG) available for sale in Intrepid:

Filtering is offered in FFT (Fast Fourier Transform) and by spatial convolution. These are whole of tensor filters (both finite impulse response: FIR and infinite impulse response IIR). Includes methods for estimating the underlying "POTENTIAL" using a moving window of 11 points.

Spherical Linear Interpolation of tensor data, or gridding (patent pending) is offered, this now includes support for the A & B horizontal components of the Falcon system. Traditional gridding algorithms always underestimates the gradient magnitude between flight lines by at least 1%, so spherical treatment is very important.

Whole of tensor denoising and smoothing locally for gridded tensor data called MITRE (Minimize Tensor Residual errors) is also offered in the Intrepid tools set. This uses third order tensor relationships. (Ideas for extending this to Falcon are under development.)

Euler deconvolution for tensors has been implemented in the Intrepid tools set. This provides an automatic method for finding a regional estimate of the density basement surface.

Innovative visualization for both profile tensor data and gridded tensor data is offered in Intrepid, including Phase Plots, and supporting dynamic zoom and the resampling of tensor gridded data.

Integration of tensor data is supported in Intrepid software, using all the measured gradient components to reinforce an estimate for the vertical component of gravity.

Interpretation workflows for Airborne Gravity Gradiometry (AGG) available for sale inIntrepid:

An automatic interpretation for 2D dyke bodies using FTG data is available in Intrepid. This gives a semi-automatic workflow that allows you to create a complex 3D geology model populated by these dykes.

Joint litho-constrained stochastic inversion of full tensor gradiometry data - available in GeoModeller software.

 

 

Clustering for tilt, dip and strike estimations in elongated surface features using FTG data is newly available in Intrepid software. See our EAGE 2016 Gravity Gradiometry Workshop PowerPoint and Clustering Paper.displaying 2005 FTG data from the Dry Hills, Crescent Valley, Nevada (thanks to Bell Geospace and CMQ Resources)

 

 

TIPS about handling Airborne Gravity Gradiometry (AGG)

We recommend a 6 band ERMapper grid to store a "tensor" grid, as all the elements of the measured signal are present in the one place, enabling innovative manipulations of the tensor signal (such as a Phase Plot) on demand. This also positions the survey data well for geological interpretation studies which usually require the signal in grid form.

The rather odd habit that the industry has of dropping off all the signal components except Gz or Gzz when an interpretation is attempted can be avoided. If you have paid for a tensor survey, you want to see all the data being employed during interpretation (about 30% of the geophysical signal magnitudes reside in the cross-components).

The Intrepid software suite can provide transforms from FTG to Falcon and vice-versa. In the case of FTG, this is trivial. In the case of Falcon data, to get the best results, we require an FFT transform on the Falcon grid, using the complete horizontal gradient in a complex form.