Improving the Local Wavenumber Method by the DEXP Transformation

In this paper we present an improvement to the local wavenumber method able to overcome its instability caused by the use of high-order derivatives. We make use of the stable properties of the Depth from EXtreme Points (DEXP) method, in which the depth to the source is determined at the extreme points of the field scaled with a power law of altitude. As DEXP transformation is applied to the local wavenumber function, we show that the scaling law is independent on the structural index. This allows the technique to be fully automatic, so that it may be implemented as a very fast imaging method, mapping every source, of different homogeneity degree, at the correct depth.