Processing with nonlinear filters satellite imagery

Abstract

This paper describes the aim towards a nonlinear processing system for satellite image enhancement and smoothing that prepares image for a successful feature extraction through edge detection. Emphasis was given to coastlines, man made objects such as airports, dams, buildings and linear features such as roads and parcel boundaries. Rank order morphological operators and adaptive filtering were employed leading to a promising result. Adaptive filtering was adopted to smooth the image, homogenize regions and at the same time prohibit edge blurring, since high frequency areas in the image are protected. Morphological operators based on rank filters were also implemented because they are often more robust to noise and shape variations than morphological operators with plain structuring element. A survey concerning the shape and the size for the structuring element used for the morphological operators is presented. Structuring element’s shape can lead to certain transformation of desired features geometry and size controls the scale space, trying to retain only features at certain desirable scales. The nonlinear processing system was applied to SPOT HRV (10-meters ground resolution) and IKONOS PAN (1-meter ground resolution) satellite imagery and is demonstrated with examples.