Hyperspectral/spatial detection of edges (HySPADE): an algorithm for spatial and spectral analysis of hyperspectral information

An algorithm for hyperspectral edge detection is presented. HySPADE (for hyperspectral/spatial detection of edges) simultaneously utilizes spectral and spatial information. HySPADE accepts as input a hyperspectral information (HSI) data cube; VNIR/SWIR radiance and reflectance spectra are used here. A transformed data cube is contructed by finding the spectral angle (SA) between each pixel in the original data cube with every other pixel in the same cube. Thus, band 1 of the tansformed cube contains the SA of the spectrum in pixel location (1,1) of the original cube with every other spectrum. Band 2 of the transformed cube contains the SA value of the pixel at location (1,2) with every other spectrum in the cube; and so on. In practice, HySPADE is applied to an N x N window of the original HSI cube; thus the transformed SA cube has dimensions of N samples x N lines x (NxN) bands. Each spectrum in the transformed SA cube contains information about spatial changes in composition of materials as they occur within the scene: the band number of each spectrum in the SA cube is easily translated into the (sample, line) address in the original HSI cube. Each spectrum in the transformed SA cube is analyzed with a one-dimensional edge-detector; a first-order finite-difference is used. Band number coordinates of detected edges are transformed back into (sample, line) addresses in the original HSI cube and mapped to form an edge-detected image. HySPADE output is shown. Extensions of the HySPADE concept are suggested as are applications for HySPADE in HSI analysis and exploitation.