13 May 2015 Joint azimuth and elevation localization estimates in 3D synthetic aperture radar scenarios
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The location of point scatterers in Synthetic Aperture Radar (SAR) data is exploited in several modern analyzes including persistent scatter tracking, terrain deformation, and object identification. The changes in scatterers over time (pulse-to-pulse including vibration and movement, or pass-to-pass including direct follow on, time of day, and season), can be used to draw more information about the data collection. Multiple pass and multiple antenna SAR scenarios have extended these analyzes to location in three dimensions. Either multiple passes at different elevation angles may be .own or an antenna array with an elevation baseline performs a single pass. Parametric spectral estimation in each dimension allows sub-pixel localization of point scatterers in some cases additionally exploiting the multiple samples in each cross dimension. The accuracy of parametric estimation is increased when several azimuth passes or elevations (snapshots) are summed to mitigate measurement noise. Inherent range curvature across the aperture however limits the accuracy in the range dimension to that attained from a single pulse. Unlike the stationary case where radar returns may be averaged the movement necessary to create the synthetic aperture is only approximately (to pixel level accuracy) removed to form SAR images. In parametric estimation increased accuracy is attained when two dimensions are used to jointly estimate locations. This paper involves jointly estimating azimuth and elevation to attain increased accuracy 3D location estimates. In this way the full 2D array of azimuth and elevation samples is used to obtain the maximum possible accuracy. In addition the independent dimension collection geometry requires choosing which dimension azimuth or elevation attains the highest accuracy while joint estimation increases accuracy in both dimensions. When maximum parametric estimation accuracy in azimuth is selected the standard interferometric SAR scenario results. When maximum estimation accuracy in elevation is selected the multiple baseline interferometric SAR scenario results. Use of a 2D parametric estimation method attains the best accuracy possible in both dimensions. When in some scenarios particularly the orbital case where the azimuth dimension is only approximately linear the full accuracy increase of linear joint azimuth and elevation is not fully attained. Images and point cloud estimates are shown for several linear and orbital SAR scenarios. Images provide a visual representation of the data while the quantitative point cloud data is a direct input for the multiple analyzes listed earlier.
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Matthew Pepin, "Joint azimuth and elevation localization estimates in 3D synthetic aperture radar scenarios", Proc. SPIE 9475, Algorithms for Synthetic Aperture Radar Imagery XXII, 94750B (13 May 2015); doi: 10.1117/12.2176779; https://doi.org/10.1117/12.2176779

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