Detection of keystone in imaging spectrometer data

Abstract

A procedure has been developed to measure the spatial mis-registration of the bands of imaging spectrometers using data acquired by the sensor in flight. This is done for each across-track pixel and for all bands, thus allowing the measurement of the instrument's 'keystone' and related inter-band spatial shifts. The procedure uses spatial features present in the scene. The inter-band spatial relationship determinations are made by correlating these features as detected by the various bands. Measurements have been made for a number of instruments including the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), Hyperion, Compact Airborne Spectrographic Imager (<i>casi</i>), SWIR (Short Wave Infra-Red) Full Spectrum Imager (SFSI), and Aurora. The measurements on AVIRIS data were performed as a test of the procedure; since AVIRIS is a whisk-broom scanner it is expected to be free of keystone. The airborne Aurora, <i>casi</i>, and SFSI and the satellite sensor Hyperion are all pushbroom instruments, exhibiting varying degrees of keystone. The potential impact of keystone upon spectral similarity measures is examined.