Image registration method based on synthetic aperture radar (SAR) image and digital elevation model (DEM) data

Abstract

The invention discloses an image registration method based on a synthetic aperture radar (SAR) image and digital elevation model (DEM) data, wherein the problems that the positioning precision to ground target points in SAR image is not high and positioning is difficult to realize in actual projects in the prior art are mainly solved. The method comprises the following steps of: solving a longitude L, a latitude B and an elevation value h' of a ground target point in a spherical coordinate system by using a steepest descent method according to the Range-Doppler (RD) principle and the earth model equation, and transforming the values into a geodetic coordinate system; looking up the elevation value h' corresponding to B and L in a DEM database, and comparing the absolute value of h'- h' with a set threshold value epsilon, if the absolute value of h'- h' is greater than epsilon, enabling h to be equal to h' and returning to resolve the equation system again, and if the absolute value ofh'- h' is identical to or less than epsilon, stopping iteration, and taking h' as the elevation value of the ground target point, and the corresponding latitude B and longitude L as the latitude and longitude of the ground target point; linearly correcting the longitude and latitude to eliminate system errors, so that a final ground target point positioning result is obtained. The image registration method disclosed by the invention has the advantages of small operand and high positioning precision, and can be used for positioning ground target points in SAR images in actual projects.

Description

technical field [0001] The invention belongs to the technical field of image processing and relates to image registration, in particular to a ground target positioning and registration method, which can be used in the preprocessing link of the ground target positioning in SAR images and the geometric correction process of SAR images. Background technique [0002] Synthetic aperture radar (SAR) technology is playing an increasingly important role in military affairs, topographic surveying and mapping, and ocean monitoring because of its high resolution, all-weather, all-weather working ability, and target recognition characteristics. Image registration is to spatially align remote sensing digital images acquired from the same area, at the same time or at different times, from different sensors or from different viewpoints. Using the image registration of SAR image and digital elevation model DEM database, the pixel of the image can be precisely positioned. The image registrat...

AI Technical Summary

Problems solved by technology

[0020] Although this method can solve the defects that the positioning method based on the polynomial model has great limitations and low positioning accuracy in practical engineering applications, and the positioning method based on the collinear equation model cannot be well used in SAR image positioning.

However, most of the solutions to this positioning method use the least squares iterative algorithm, the solution process is complicated, and the height h of the target point is unknown during the solution process, so the ground target position vector (x t ,y t ,z t ) to represent and then calculate the height h

At the same time, the coordinate conversion of the calculated ground target position vector is carried out, so that in the process of solving, since the known data such as the earth's equatorial radius and the earth's polar radius are approximate data, the error of the calculation result will be enlarged to make the positioning Reduced precision and no way to verify the plausibility of the resulting data

Images