Calibration method of polarimetric synthetic aperture radar based on natural bare soil

Abstract

The invention discloses a polarization synthetic aperture radar calibration method based on natural bare soil. The method comprises the steps that the crosstalk and cross polarization channel imbalance parameters of a POLSAR radar image are estimated and removed at first; then, the POLSAR radar image is parted in the distance direction and the azimuth direction; finally, an optimization function is built with the low spirochete ingredient of real soil as an optimization object, and imbalance of a same polarization channel is solved through the characteristic that blocks in the same distance direction have the identical unknown numbers. The weak scattering characteristic of the spirochete of the natural bare soil is utilized, calibration is carried out on emission and receiving distortion matrixes existing in a POLSAR radar system, biased observed values are re-calibrated to be a real scattering matrix, and powerful guarantees can be provided for a radar in the application aspects of territorial resources surveys, natural disaster emergency responses and the like.

Description

technical field [0001] The invention belongs to the technical field of radar remote sensing image processing, and in particular relates to a calibration method of a polarimetric synthetic aperture radar (POLSAR) based on natural bare soil. Background technique [0002] As an advanced synthetic aperture radar technology, POLSAR (Polarization Synthetic Aperture Radar) obtains the ground object scattering matrix by transmitting and receiving horizontally and vertically polarized electromagnetic waves, and performs land observation under all-weather and all-weather conditions, making up for other remote sensing methods. Insufficient, it effectively assists the classified survey of land resources and obtains physical parameters such as vegetation biomass and surface humidity. The information observed by POLSAR is often affected by the transmission and reception distortion matrix of the system, which makes the observed value deviate from the real value. The distortion process can...

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Problems solved by technology

[0003] Existing polarization calibration methods use the reciprocity and scattering symmetry of natural objects to correct crosstalk and cross-polarization channel imbalance without reference targets; for co-polarization channel imbalance, the existing Calibration methods require at least one active or passive corner reflector to be deployed in the scene for calibration, and it is often difficult to deploy corner reflectors in some undulating mountainous areas (such as western my country) and uninhabited desert areas

Foreign machine-spaceborne polarimetric synthetic aperture radar hardware systems are reliable and stable, and the image amplitude error is often less than 0.5dB and the phase error is less than 5 degrees when the unbalanced calibration of the co-polarization channel is not performed, which can meet the most basic land observation accuracy requirements; The errors of my country's electronic hardware systems are often high, and the data without polarization calibration is difficult to meet the basic needs of remote sensing, which seriously restricts the application range of my country's POLSAR system

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