Automated extraction of airport runway patterns from radar imagery

Abstract

Image processing for extracting terrain features from an image formed of an array of pixels is disclosed. In a particular embodiment, each pixel in a neighborhood is averaged in a direction which is most homogeneous thereby preserving and smoothing edges of the image. Edge detection in orthogonal directions is applied for defining the magnitude and direction of edges at each pixel. After edges are defined each pixel is compared with pixels in a neighborhood for determining the probability that the pixel is on an edge and the angle at which such edge is disposed. Probable edges are reinforced and non-probable or non-edges are eliminated. Reinforced edges are thinned to a minimum of one pixel without eliminating its connectivity with any adjacent pixel on the edge. Components consisting of pixels of a similar kind which are connected are identified and uniquely labeled. At least two properties of each connected component are calculated including area and spread. Connected components which fall within predefined limits indicative of a desired feature are selected. Borders of each component are identified and selected pixels are eliminated. Pixels in each border are encoded and thereafter converted into a series of straight line segments by polygon approximation. The image may be displayed or stored in a data base for later utilization.

Dependencies are inferred from the claim text.