Euler–Bessel and Euler–Fourier transforms

We consider a topological integral transform of Bessel (concentric isospectral sets) type and Fourier (hyperplane isospectral sets) type, using the Euler characteristic as a measure. These transforms convert constructible Z-valued functions to continuous R-valued functions over Rn. Core contributions include: the definition of the topological Bessel transform, a relationship in terms of the logarithmic blowup of the topological Fourier transform and a novel Morse index formula for the transforms. We then apply the theory to problems of target reconstruction from enumerative sensor data, including localization and shape discrimination. This last application utilizes an extension of spatially variant apodization to mitigate sidelobe phenomena