A Fast Approximation Method of Median Filtering for SAR Image

Abstract

The invention discloses a median filtering fast approximation method for SAR images. According to the characteristics of multi-view SAR intensity images that approximately obey the Gamma distribution, the intensity images are converted into amplitude image forms, and the global maximum and minimum values ​​of the amplitude images are counted to obtain Estimate the interval range where the median value of the amplitude image is located, and linearly quantize the amplitude image to several gray levels based on this range, and then search for a gray level with a cumulative distribution function value of 0.5. When the number of pixels located within this gray level When the number is small, the average value of the pixel intensity of this level is taken as the final result of median filtering. Otherwise, the intensity images of this level of pixels are finely sorted. This invention quantifies the median value in a small range of the amplitude domain, which is helpful to The median value is accurately located, and the calculation amount is basically independent of the number of elements that need to be sorted. Therefore, the search calculation amount can be greatly reduced, and the problem of low efficiency of median filtering in large windows and multi-temporal SAR images is solved.

Description

【Technical field】 [0001] The invention relates to the technical field of remote sensing image processing, and relates to a synthetic aperture radar (Synthetic Aperture Radar, referred to as SAR) image coherent speckle noise suppression method, specifically a median filter fast approximation method for SAR images. 【Background technique】 [0002] Synthetic aperture radar is not limited by factors such as weather, geography and time. It can perform high-resolution imaging on the ground and has certain penetrating power. Therefore, it is widely used in military reconnaissance, resource detection, environmental monitoring, surveying and mapping, and geographical conditions. Monitoring and other ground remote sensing applications. With the successful launch of many radar satellites, time-series radar images have become an important aspect of current remote sensing applications. [0003] Since SAR works based on the coherent imaging mechanism, serious speckle noise exists in the S...

AI Technical Summary

Problems solved by technology

[0007] The technical problem to be solved by the present invention is to provide a fast approximation method for median filtering of SAR images, that is, to solve the problem of low calculation efficiency of multi-temporal or large sliding window median filtering in SAR intensity images. The present invention is based on multi-view SAR The intensity image approximately obeys the characteristics of the Gamma distribution. First, set the sliding window parameters, convert the intensity image into an amplitude image, and count the maximum and minimum values ​​of the amplitude image, and then estimate the interval of the median value of the amplitude image, and based on this range The magnitude image is linearly quantized to fewer gray levels, in order to accurately locate the gray level of the median value of the magnitude image by calculating the sliding window distribution accumulation function, and effectively improve the calculation efficiency of the median filter

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