Usually, a standard least-squares image-matching functional model has radiometric shift and drift parameters, and geometric affinity parameters. This paper is focused to improve on a conventional stochastic modeling. Single-difference gray-levels are no longer dealt with to be independent and identically distributed. Scaling variance and covariance components are associated with some processed image segments. The estimated variance and covariance components are then used to form a new measurement covariance matrix, leading to iteratively adjusted weights until a steady parameter state is achieved. In theory, the proposed Blue-estimator is akin to the best invariant quadratic unbiased estimator. In practice, two Radarsat-1 synthetic aperture radar image scenes were made available to study an image-matching applicability to features such as an angular section of a pond and an intersection of roads. As a result, both the line and sample coordinates can be determined more accurately.