The ’DIRECT’ Algorithm for the Efficient Estimation of Mean Deformation Velocity with PSI

Permanent Scatter Interferometry (PSI) is a established technique to measure terrain deformation. In order to monitor natural disasters and to better understand their causes and impact, it is important to precisely estimate the mean velocity of the terrain deformation, eventually making use of higher order deformation models. The estimation is usually performed using Grid-Search (GS) to find the location of the maximum of the periodogram, operation which may be very time demanding depending on the densities of the Persistent Scatter (PS) grid and of the stack. In this paper we propose the use of the Dividing Rectangles (DIRECT) optimization algorithm as an alternative to GS. DIRECT offers a good balance between local and global search, largely reducing the number of evaluations of the optimization functional. The approach was tested with different datasets and the mean velocity could be determined more precisely and faster than GS (speedup up to 20 was obtained).