Along-track InSAR (AT-InSAR) is a special mode of interferometric SAR (InSAR) where the individual SAR images have been acquired from the same flight track. With virtually identical geometric configuration of the individual SAR images, the measured phase difference is dominated by temporal changes occurring between the acquisitions. Consequently, AT-InSAR can be used to measure the displacement and/or radial velocity of targets on the ground, with the temporal offset between the acquisitions determining the time scale of the measurements. AT-InSAR can be implemented using one or more SAR sensors, in both single-pass and repeat-pass configurations, accommodating various needs. Using at least two sensors in a single-pass configuration allows the measurement of relatively high velocities, e.g., for vehicles and ocean waves. Conversely, using at least one sensor in a repeat-pass configuration allows the measurement of low velocities or displacements, e.g., for glaciers and due to volcanoes, earthquakes, subsidence, and landslides.