A novel extension of the anisotropic rotation-invariant built-up presence index to SAR data

Although the mechanisms underlying remote sensing images by optical and SAR sensors are very different, specific environments are represented on both types of imagery as largely similar spatial patterns. The anisotropic rotation-invariant built-up presence index makes use of these patterns on optical imagery for delineating and characterizing human settlements. This paper focuses on the necessity of a different definition for this index when it is applied to SAR data. Although the extension from optical to radar data is not straightforward, the formulation proposed in this paper makes it suitable for a good characterization of large urban areas and small informal settlements as well. After introducing and validating the slant-range version of the anisotropic rotation-invariant built-up presence index, a comparison of its effectiveness with respect to different radar viewing geometries and frequencies on the same test area is carried out, suggesting that the methodology works well in any situation.