*3.4. Comparison of VLM and LOS Velocities and GNSS Data*

The trends in vertical land movement measured at the GNSS stations located in Santa Marta and Barranquilla were contrasted with VLM and LOS velocity values from InSAR pixels located nearby these stations. Every four years, daily readings for each station were processed by the Deutsches Geodätisches Forschungsinstitut (DGFI) to provide long-term displacements for a network of permanent stations in South America. Roughly matching the time span for ALOS data, a solution for 2006–2011 compiled for the GNSS station in Santa Marta (Figure 2), indicated a vertical displacement of −0.52 cm/yr for that period [58]. For the same area, LOS velocities of −0.12 cm/yr were found for ALOS data. For the GNSS station in Barranquilla, vertical displacements of −0.14 cm/yr were reported for 2007– 2009 [58], whereas a value of −0.31 cm/yr was obtained for the ALOS LOS velocities for 2007–2011. Sentinel data is not available for these years. For the period 2017–2021, VLM estimates using Sentinel-1A/B data near the Santa Marta station are −1.31 cm/yr. An updated processed solution for the GNSS stations to contrast the above values is not available yet.
