Persistent Scatterer Interferometry (PSI) is a time series remote sensing technique to estimate displacements of geo-objects from the interferometric phases of selected Persistent Scatterers (PS). The relative position of a scatterer within a resolution cell causes an additional phase contribution in the observed phase, which needs to be accounted for in PSI processing. Here we analyze the influence of this sub-pixel position correction on point localization and displacement quality. Apart from a theoretical evaluation, we perform experiments with TerraSAR-X, Radarsat-2, and Sentinel-1, demonstrating various levels of improvement. We show that the influence of the sub-pixel correction is significant for the geolocation of the scatterer (meter-level improvement), modest for the elevation estimation (centimeter-level improvement), and limited for the displacement estimation (submillimeter-level). For displacement velocities, we find variations of a few tenths of a millimeter per year. The effect of sub-pixel correction is most dominant for large orbital baselines and short time series.

持久散射体干涉测量法（PSI）是一种时间序列遥感技术，用于根据选定的持久散射体（PS）的干涉相来估算地理对象的位移。分辨率单元内散射体的相对位置会在观察到的相位中引起额外的相位贡献，这需要在PSI处理中加以考虑。在这里，我们分析了此子像素位置校正对点定位和位移质量的影响。除了进行理论评估外，我们还使用TerraSAR-X，Radarsat-2和Sentinel-1进行了实验，展示了不同程度的改进。我们表明，子像素校正的影响对于散射体的地理位置（米级改进）是显着的，对于高程估计（厘米级改进）是适度的，并且仅限于位移估算（亚毫米级）。对于位移速度，我们发现每年的变化幅度仅为十分之几毫米。对于较大的轨道基线和较短的时间序列，亚像素校正的效果最为明显。