Interferometric Synthetic Aperture Radar (InSAR) is a remote sensing and geodetic technique for ground deformation measurements using radar images of the Earth's surface that are collected regularly by orbiting satellites equipped with SAR sensors. Natural reflectors on the ground which backscatter the radar signal to the satellite are monitored at different time and changes of the line of sight (LOS) distances can detect ground surface movements. Natural reflectors are abundant in many places, especially in urban areas. However, areas that are densely vegetated or covered by snow have limitations for InSAR technique and therefore artificial corner reflectors, passive, or active ones, can be used instead. These corner reflectors are devices which provide precise measurement points and can be installed at selected locations. These devices can measure temporal LOS changes of the measurement point precisely using the InSAR technique.

Since 2020, Lantmäteriet has installed three active electronic corner reflectors (ECR) and several types of artificial passive reflectors (CR) in different locations of Sweden. The corner reflectors are anchored to the bedrock like GNSS stations using metal masts. The installation is in progress and the plan is to continue and complement the national geodetic infrastructure with at least 20 passive corner reflectors which are collocated with permanent GNSS stations and/or tide gauges and/or absolute gravity points. Among other applications, these collocated points link different geodetic measurement techniques, including InSAR and GNSS, and contribute to the development and validation of the national and European ground motion services. Moreover, the GNSS derived velocities and the LOS temporal variations measured on the nearby corner reflectors are useful to transform the relative ground motions estimated with InSAR to an absolute geodetic reference frame.