Does intrepid have special methods designed for potential field tensor gradiometry?
Intrepid has spent over five years designing and shipping geophysical tools to properly respect and handle potential field data and its gradients, including tensor gradients.
In practice, the actual gravity gradient survey data you might have mostly comes from an instrument built by Lockheed Martin to Fugro (Falcon), Bell Geoscience and ArcEx. Falcon is a partial horizontal tensor gradient measurement and the other modern measures are Full tensor gradient (FTG) measurements.
Typically, the larger the inertia of the measuring aircraft, the better the signal. Also, there are older analog electronics still being used in some instruments that are not as stable or as reliable as the newer fully digital electronics. A next generation of hardware is in design and build during 2011, for release in 2012.
Workflows for both variations are available for sale in the Intrepid tool sets.
- Filtering in FFT and by spatial convolution, so these are whole of tensor FIR and IIR filters, methods for estimating the underlying "POTENTIAL" using a moving window of 11 points.
- We hold a patent for spherical linear interpolation of tensor data (gridding). Note, this now includes the A & B horizontal Falcon system. We have shown all traditional gridding algorithms always underestimates the gradient magnitude between flight lines by at least 1%.
- We have a newly developed whole of tensor denoising and smoothing locally for gridded tensor data called MITRE (Minimize Tensor Residual errors). This uses third order tensor relationships. Ideas for extending this to Falcon are in existence.
- We have implemented euler deconvolution for tensors. This gives you an automatic method to find a regional estimate of the density basement surface.
- We have innovative visualization for both profile tensor data and gridded data. This includes Phase plots. We support dynamic zoom and resampling of tensor gridded data.
- Integration of tensor data is supported, using all the measured gradient components to reinforce an estimate for vertical component of gravity.
- Recently, an automatic interpretation for 2D dyke bodies has been added that uses FTG data. This gives a semi-automatic workflow that allows you to create a complex 3D geology model populated by these dykes.
- 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, that usually require the signal in grid form.
The rather odd habit that 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.
- We give transforms from FTG to Falcon and vice-versa. In the case of FTG, this is trivial. In the case of Falcon, we require a FFT transform on the Falcon grid, using the complete horizontal gradient in a complex form, to get the best result.