SAR image quality evaluation

SAR Image radiation quality evaluation index

The program is based on SAR Imaging mechanism and digital image processing principle , Two kinds of evaluation are realized SAR Calculation index of image radiation quality ——SAR Image radiation resolution and SAR Equivalent number of images .

1. SAR Image radiation resolution

The radiation resolution describes the radiation quality of each pixel , That is, the ability to distinguish the backscattering coefficient of the target . It's a measure SAR A measure of the resolution of image gray level , It is equivalent to the ability to distinguish different gray levels in black-and-white photos , Its quality directly affects SAR Image quantification and interpretation application . The size of the radiation resolution is determined by the target coherent speckle and signal-to-noise ratio . Its calculation formula is as follows ：

among ,μ and σ Each represents a piece SAR The mean and standard deviation of the intensity information of the image area .

2. SAR Equivalent number of images

Equivalent visual number is also a measure SAR The relative intensity of speckle noise in the image Indicators of , It can characterize the ability of the image to distinguish regions with different backscattering characteristics . The greater the equivalent number of views , It indicates that there are spots on the image The weaker the noise . The equivalent number of views depends not only on SAR Satellite specific work Pattern , It also depends on SAR Ground workstation for image preprocessing . This means that the equivalent number of views should be estimated from the image itself , Or treat it as a function of working mode and ground workstation parameters through a series of image calculations . Its calculation formula is as follows ：

In style ,μ and σ Each represents a piece SAR The mean and standard deviation of the intensity information of the image area ,ENL Is the equivalent number of views of the uniform area of the image (Equivalent Number of Looks, ENL)

3. The feasibility of

For radiation resolution , Dongge [2] Through numerical analysis , Point out the purpose Before the application of SAR The engineering estimation formula of image radiation resolution can only be qualitatively analyzed SAR Signal to noise ratio of single view image and multi view number pair SAR Image radiation The effect of resolution . Dongge also derived a new SAR Engineering estimation formula of image radiation resolution , Through theoretical and numerical analysis, it is proved that the error is significantly smaller than the currently applied engineering estimation formula and is suitable for quantitative analysis .

4. reference

[1] Wang Zheyuan , Li Yuanxiang , Yu Wenxian . SAR Overview of image quality evaluation [J]. Remote sensing information , 2016, 31(5):10.

[2] Dongge . Correction of engineering estimation formula of radiation resolution of synthetic aperture radar image [J]. Journal of electronics and information , 2004, 26(12):7.