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There are four main steps to forming an interferogram. The first step is co-registration, which aligns two SAR images as accurately as possible. The second step is forming the interferogram itself, which involves reducing noise and converting the values to the continuous phase. The third step is unwrapping, which makes the result easier to interpret. The final step is dual-coding, which is done in the radar reference frame but can be transformed to the geodetic reference frame for use. There are four fundamental steps to forming an interferogram. Actually, there are additional steps, such as filtering, but the detailed processing steps depend on different software packages. Here, the four steps are the general steps that most software packages apply. In the state of co-registration, two SAR images are aligned as accurately as possible. In reality, every time SAR satellite passes through the same region, it cannot measure the same region precisely. Two SAR images may have offset. If two SAR images are not aligned accurately and are directly used to form an interferogram, interference may be implemented between two faces at different pixels. The random components at different pixels are different, so it cannot obtain useful information. The state of co-registration aims to align two or more SAR images as accurately as possible. The state of the interferogram is just a three-step thing. It forms interferograms. During these steps, it usually adopts multi-look to reduce noise. After forming interferograms, the values are within minus pi to pi. It is not intuitive to interpret or view this kind of result, so we convert it to the continuous phase. The process is called unwrapping. The final step is dual-code. Here, both steps are processed in the radar reference frame. If you want to use the result, it is convenient to transform the radar reference frame to geodetic reference frame.